PLATINUM METALS REVIEW

UK ISSN 0032-1400

PLATINUM METALS REVIEW

A quarterly survey of research on the platinum metals and of developments in their application in industry

VOL. 30 OCTOBER 1986 NO. 4

Contents

Corrosion Prevention in Concrete

Some Platinum Group Metals Cluster Catalysts

Commodity Meeting on Platinum

Striving to Advance Platinum Technology

High Pressure Ammonia Oxidation

Energy Storage and Transmission

The Platinum Prints of Peter H. Emerson

Organometallic Chemistry of Palladium

Sintering Aids in Powder Metallurgy

Oxidation Behaviour of Some Platinum Alloys

Tenth International Precious Metals Conference

Alexander Abramovich Grinberg

Abstracts

New Patents

Index to Volume 30

Communications should be addressed to

The Editor, Platinum Metals Review Johnson Matthey Public Limited Company, Hatton Garden, London EClN 8EE

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Corrosion Prevention in Concrete THE CATHODIC PROTECTION OF REINFORCING STEEL BARS USING PLATINISED-TYPE MATERIALS

By P. C. S. Hayfield IMI plc, Research and Development Department, Birmingham

The cathodic protection of steel reinforcing bars in concrete to prevent their corrosion, brought on principally by de-icing salts used on roadways, is at the interesting stage where technology is barely keeping pace with practical demand. I t already seems likely that platinum and other noble metals, used in conjunction with titanium and niobium, will play a vital role in several of the protection systems that appear to be the forerunners in a rapidly developing industry.

Reinforced concrete is used in numerous ways, some of the larger and better known uses including roadways, bridges, car parks, residential buildings and in industry; for example it is widely used in nuclear power plant. It is in general an excellent construction material (I). Concrete alone is good in compression, but reinforced concrete greatly increases the scope for making structures required to withstand other forms of mechanical force.

In a small percentage of instances reinforced concrete may deteriorate prematurely, but so widespread is the use of the material that problems can be encountered in a wide range of individual applications. It is reliably reported that in North America there are now some 300,000 concrete bridges requiring repairs, with costs estimated in terms of billions of dollars, in addition to the roadways and car parks requiring remedial attention. There are also lesser but significant problems with reinforced concrete in Europe and the Middle East. From a financial aspect the future costs over the next few decades for repairs and replacement throughout the world are likely to be staggeringly high.

One is tempted to ask why, if reinforced concrete has been used for so long, is it only now that problems are arising, predominantly, though not exclusively, associated with corrosion of the reinforcing steel bars, or rebars as they are commonly called. While it is

dangerous to make generalities, the reasons would seem to be that since World War I1 the volume of reinforced concrete has greatly increased and so also has the amount of salt used on roads, salt being a major cause of rebar corrosion. For example, in the U.S.A. from 1955 to 1970, the amount of de-icing salt used increased by an order of magnitude, and it continues to increase. Such is the insidious nature of salt in concrete that it requires an ingestion period of 10 to 20 years for the damage to make itself evident.

Degradation of reinforced concrete shows up in a variety of ways. Corrosion of rebars produces a bulky reaction product that puts pressure on the surrounding concrete cover which first cracks and eventually spalls. Spall- ing of the cover gives rise to possible injury, particularly for example in the case of high rise flats or bridges, but extensive corrosion of the rebar itself will lead to mechanical weakening of the reinforced structure. The ultimate result can be collapse of the structure, and disquieting examples have, in fact, occurred.

While the commonest cause of rebar corrosion arises from the use of de-icing salts on roadways, chloride contamination can also arise from setting additives such as calcium chloride put into the concrete during mixing, or by the accidental use of contaminated make-up water. Most salt corrosion problems occur in the so-

Platinum Metals Rev., 1986, 30, (4), 158-166 158

Fig. 1 Reinforced concrete is widely used as a constructional material for structures that are required to withstand more than simple compressive forces. This section of motorway viaduct in the English Midlands is just one example of the many crucially important uses of the material

Fig. 2 Premature deterioration of conrrete can result from corrosion of the steel reinforcement bars. Commonly this is due to the action of de-icing salts on finished structures, but it may also be caused by chloride-containing setting additive or contaminated make-up water. Bulky reaction products can result in spalling of the concrete cover and mechanical weakening of the whole structure

Platinum Metals Rev., 1986, 30, (4) 159

called Northern Hemisphere snow belt area. However, problems are also rife around the Arabian Gulf, for example, in hot humid conditions where sea-water laden winds deposit salt on roadways and buildings, and where water supplies are also high in chloride, the higher environmental temperature accentuating the rate of rebar corrosion.

Porosity in Concrete Most concrete is porous, this being in the

form of interconnecting micropores, and in consequence pore water will have access to embedded rebars. Due to the chemistry of concrete, pore water is usually highly alkaline at pH 12 to 13 and this high alkalinity is responsible for the inertness generally exhibited by rebars in concrete, steel under such conditions forming a stable protective oxide film (2).

When reinforced concrete is being made up, it is not uncommon to observe that the rebars are already rusted. Provided the rust is adherent, it is said that this helps to promote a good bond between rebar and concrete. Exposing the surface of a rebar that has been embedded in concrete for some time shows that the rust layer on the steel has transformed to a hard, shiny, dark, protective film which renders the steel perfectly stable from a corrosion viewpoint.

With concrete exposed to humid or wet conditions, and with salt contamination, a situation eventually arises where the steel, irrespective of the high pH, is exposed to oxygenated chloride- contaminated water. These are conditions that can give rise to corrosion of steel, often by localised pitting attack (3). That this is the case can be judged by measuring the electrode potential of the rebar (4), but because of the concrete cover this cannot be done directly. None the less, indications of the so-called ‘mixed’ potential of the rebar can be obtained by measurements taken on the outer surface of the material. Indeed, electrode potential mapping of concrete structures is now commonly used to reveal corrosion in a structure at locations where it might be expected to occur preferen- tially, and sometimes to detect corrosion in areas where its presence was not anticipated.

It will not be possible to overcome rebar corrosion by introducing a non-porous form of concrete on a large scale so the use of more corrosion resistant materials such as galvanised or stainless steel rebars, is being considered. Some countries, including Sweden, have banned the use of de-icing salts on roads, and Austria seems likely to follow.

Salt contamination of existing structures, however, is now an immense problem. On a practical scale there is no ready possibility of expelling chloride or other activating ions. Several years ago research was carried out to show that, on a pilot scale, salt contamination could be removed electrochemically (9, but so far it has proved impractical to apply this technique in the field; thus the engineer is still left with the unenviable task of deciding what to do with salt contaminated porous concrete containing corroding rebars (6- 13).

Solutions to the Problem of Corroding Steel Reinforcement

There are a number of options for resolving the problems. The structures could be rebuilt and steps taken to ensure no further salt contamination, but applied to a motorway, for instance, this could be far too expensive. Another option is to uncover the corroding rebar, remove the corrosion product, or even weld in new reinforcement, and then repair with a low porosity concrete, all of which can be difficult and expensive work. Yet another option is to seal the outer surface of the concrete, for example with silicones or polymer concretes, so that no further oxygen, chloride ion or water is per- mitted into the structure, any activating products inside eventually stifling themselves; but even this is considered impractical on a large scale.

The consensus view seems to be that the only real practical option left is to arrest rebar corrosion electrochemically by the application of cathodic protection.

Cathodic protection has been described several times in past articles in this journal (14- 16). It is a corrosion prevention method based upon the fact that iron held at a specified


negative electrode potential is immune from corrosion, for all practical purposes. There is a long history of the successful application of cathodic protection to steel structures such as oil rigs, oil well casings, oil pipelines and storage tanks, the hulls of ships and buried pipelines.

Impressed Current Cathodic Protection

The cathodic protection of rebars, on any scale, is unlikely to be based upon the use of consumable zinc, aluminium or magnesium electrodes which make use of the principle that the galvanic difference between these metals and iron will allow sufficient depression of the iron electrode potential for cathodic protection to occur. This is because the available driving force in terms of volts is too small to cope with the resistance of the concrete cover. In contrast impressed current cathodic protection, using non-consumable anodes, allows whatever cell voltage is necessary to drive the required current density of reaction.

However, impressed current cathodic protection to concrete raises special problems including: (I) The resistivity of the concrete, which will depend upon concrete type and quality. Sea- water has a resistivity of 3oQcm whereas concrete might possess values up to 20,oooQcm or more. Also, because the mobility of electrolyte in concrete is limited, some areas of the concrete may have high salt contamination while others have almost none; thus large differences of resistivity can occur in the pore water electrolyte of even relatively small concrete items. (2) The location of the counter electrode anodes is limited. They need to be applied either to the surface or at only a shallow depth. A fundamental problem arises because anodes operating in aqueous systems produce H + ions or acidity through decompositon of the water. In most environments acidity would dissipate without problem, but in concrete such acidity is almost certain to react with the free alkaline content of the concrete. Thus the very real possibility exists that acid attack around anodes might lead to as much damage to the concrete

as cathodic protection of the rebars is helpful in preventing corrosion.

There is little prior art relating to anodes in or on concrete which the cathodic protection engineer can turn to for guidance. Perhaps the closest experience is in electro-damp-proofing where small anodes are embedded in brickwork or masonry. Anodes have been observed to produce high acidity in the mortar immediately surrounding them, usually necessitating the use of specially developed forms of acid-resisting platinum electroplated titanium anodes, and an appropriate fixing technology.

In the cathodic protection of rebars in concrete, the cathode reaction is fairly predictable with some slow evolution of hydrogen accompanying the lowering of the electrode potential to values which will protect the steel. There has been concern that hydrogen evolution might lead to embrittlement of the steel or break-up of the steelkoncrete bond, but this does not seem to be a major problem area.

Reactions at the anode counter electrode are more difficult to forecast, and will depend upon the level of salt contamination, current density and electrochemical characteristics of the anode. The major reactions will be chlorine and oxygen gas evolution, the latter being accompanied by H+ ion production or acidity. What happens to the acidity is debatable.

The Practical Application of Cathodic Protection to Rebars

How cathodic protection of rebars is applied in practice is determined more by what is prac- ticable than by design. By this is meant that in most cathodic protection systems careful con- sideration is given to the siting of the anodes to give the throwing power required for effective protection. In contrast the way that the problems of

reinforced concrete have been tackled has been to cover the available surface with as much anode as possible, irrespective of the positioning and depth of the underlying rebars. Inevitably with such systems that part of the anode blanket coverage nearest to a rebar and separated by the most conductive concrete is


the part most likely to operate at highest current density, giving rise to the greatest acid attack of the underlying or adjacent concrete, which has a bearing on the life of the system.

The Indirect Use of Noble Metals The majority of systems proposed to-date use

carbon (or graphite) as the primary anode material, which is usually called the ground bed. This can be a coke/asphalt mix, a paint or in some other form. To this ground bed are attached electrical connections, which may be carbon fibre strands, lumps of silicon iron or some form of platinised titanium or platinised niobium. Often these are misleading!y named secondary anodes, but the terminology may not be too inapt if the network does not make con-

tinuous contact to the carbon, because then it becomes the primary anode and needs to have appropriate durability to contend with such an eventuality.

Some examples illustrating techniques that involve platinised materials are now given.

The Saw-Cut Method For concrete roads without an asphalt cover,

grooves are cut into the surface at intervals of approximately 300mm, the cross-section of the grooves being about 25mm x 25mm (17- 19). This separation is selected on the basis of a rule of thumb figure of 15omm for the throwing power of an anode in concrete, though clearly this figure will depend upon the many factors that can affect the electrical conductivity of

(A )

I 11 I

in the concrete structure

Fig. 3 The noble metals may be used in a number of indirect ways for the cathodic protection of rcbars. Plans and cross-sections showing three of the ways in which they are used in conjunction with carbon or graphite primary anodes (ground beds) are illustrated. (A) Grooves are cut into the surface of concrete roads, the grooves are filled with carbon and electrical contact is made by platinum-clad copper-cored niobium wire. (B) Here the concrete surface is first cleaned, then one or more layers of carbon pigment paint are applied. Electrical connection to the paint is made by means of a grid of conductor wires which is pinned to the surface and overlaid with further layers of conducting paint. (C) The concrete surface is covered with a layer of partially conducting carbon-containing concrete, applied by spraying (guniting); this encapsulates a network of platinised wire which serveu as the electrical conductor, and is overlaid by another layer of normal concrete to provide durability


concrete. Into each groove is placed the carbon- based ground bed, and electrical connection is achieved using metallurgically co-processed platinised copper-cored niobium wire (20).

Because the roadway is used without further cover over the slots, there is a risk that the backfii will work out of the grooves due to the constant movement of vehicles, and to prevent this the U.S. Federal Bureau of Highways has developed a suitable backfill formulation.

For this application the predominant type of anode is platinum-clad copper-cored niobium wire I to zmm in diameter which is produced in coils of hundreds of metres by a process developed by IMI Titanium Ltd. (20). The material begins as a metal billet IOcm or more in diameter by zocm or more in height; this is composed of a copper core, with first a niobium sleeve and then an outer coating of wrought platinum (20). Subsequently these billets are hot extruded to take the form of the massive anodes used in North Sea Oil platforms, and illustrated in Figs. 5, 6 and 7 of Shreir’s article ( I 5). Such material can also be further reduced to form fine wire coated with a pore-free layer of wrought platinum, perhaps o.5pm thick. Should any breaks occur in the coating due to scratching or bending, the underlying niobium provides high corrosion resistance to any adjacent acidity which may possibly develop during use, and it is also able to withstand high electrical stress in the presence of chloride ions.

High Carbon Paint The saw-cut method is applicable to road-

ways (pavements in American terminology) and also to other concrete forms such as crossbeams and pillars, but there are other more appropriate techniques of which the paint method is proving a popular choice (21). In this technique the concrete to be protected is first cleaned down, say by grit blasting, any urgent repairs to the cover effected, and then one or more layers of an 80 per cent carbon (graphite) pigment paint are applied. To achieve electrical connection to the paint, a grid of conductor wires is then pinned to the surface. The grid may take the form of a mixture of carbon fibres or

platinum electroplated titanium (22) or metallurgically co-processed forms of wire (20). The connection to the paint is enhanced by further layers of electrically conducting graphite paint which are applied so that the wire current distribution network becomes embedded in the paint layer. High carbodgraphite containing products are black, and because a coating of black paint is aesthetically undesirable on many structures, particularly public buildings, the black electrically conductive paint is overlaid with a more attractive, lighter-coloured, conventional electrically non-conductive paint..

Carbo-Concrete This material is partially electrically conduc-

ting due to the high percentage of carbon with which the concrete is loaded. Generally the electrical connection is made by means of a platinised titanium conductor wire.

The Direct Use of Noble Metals and Noble Metal Oxides

In the previous section reference has been made to the use of platinised titanium or platinised niobium conductors for the distribution of electricity to the electrocatalyst, which is essentially carbon, and that if the contact between carbon and feeder arrangement fails for any reason, such as slow conversion of the carbon to carbon monoxide/dioxide in the anodic reaction, then the platinised material takes over as the primary anode. It is logical to think that if a network of platinised wires could be arranged, at an economically attractive price, then it should be possible to dispense with the carbon. This is precisely what has happened, and it seems to be the developing trend. The material, which might be likened to wire netting, is a very open form of titanium mesh, typically having a metal cross-section of 1mm2 with holes of 100mm by 50mm. Such a mesh is included in Figure 4.

The mesh requires a special coating designed not only to accommodate an appropriate electrocatalyst, but also to make the overall product acid resistant. The wire and netting illustrated in Figure 4 is coated with an iridium-based


Fig. 4 These are some examples of the platinised titanium-type materials used in the cathodic protection of reinforcing bars in concrete. The coil of wire at the front right is metallurgically co-processed platinum-clad copper-core niobium (courtesy of IMI Titanium Ltd.). The coil of wire front left is platinum electroplated titanium wire, while the centre coil of wire and the roue of netting are iridium- based coated titanium (courtesy of Marston Palmer Ltd.)

material which is a preferable electrocatalyst to platinum in respect of durability under oxygen evolution conditions. There are now at least two other similar products commercially available using alternative electrocatalysts.

The wire netting type of product can be used for most applications. For example it can be laid down on roadways, on the floors of car parks, and wrapped around columns or cross beams. The coated mesh is attached by clips to the concrete and is then overlaid with a concrete cover which is applied by spraying.

Methods Not Involving the Noble Metals or Their Oxides

For the sake of completeness other methods that are being proposed are now mentioned, even though they do not involve platinum, other noble metals, or their compounds. Electrically Conducting Titanium Oxide.

The anode is a porous electrically conductive ceramic looking much like graphite but in fact composed of a particular form of titanium oxide (23, 24). Localised anodes of this material are mounted at approximate 3ocm intervals at positions midway between underlying rebars, and are connected to each other, and to the electrical supply, by a means of a network of thin titanium strip or wire. Coke/Asphalt/Sicon Iron. To cathodically protect the steel mesh rebar over a road surface, the road surfacing is removed to expose the underlying concrete and allow repairs to be made to any exposed damaged cover. Onto this is placed a layer of coke/asphalt. The electrical connection to the coke is made by flat pancake anodes of silicon iron with conventional electrical lead connections. The silicon iron is overlaid with further ground bed and the normal road surface applied (25).


Carbon Loaded Polymer. Yet another method based upon carbon involves a copper conductor wire which is covered with a thick coating of a carbon-loaded plastic. In terms of metals, the carbon loaded plastic is not very electrically conductive, but it is entirely adequate for passing the low currents required in the cathodic protection of rebar. This rope-like anode is attached over the surface of the concrete to be protected by means of suitable furings and it is then embedded in a few centimetres depth of sprayed on concrete (26).

Discussion There are now a number of competing im-

pressed current cathodic protection systems for arresting the corrosion of rebars in concrete; some of these have been under trial for a number of years while others have only recently been introduced. Specifications are being updated continuously to ensure that the most updated technology is invoked in new systems (27). But just as it may take a number of years for salt corrosion of rebars to result in significant degradation of reinforced concrete, so it takes several years to prove not only the effectiveness of cathodic protection systems but also

their long term durability in actual service. Most cathodic protection of rebars in con-

crete systems have been installed and operated in North America, with no more than a few examples in the U.K., mainly to protect buildings. The deterioration of reinforced concrete roads and bridges is less of a problem in the U. K. because of the more widespread use of asphalt-type coverage, especially over bridges. This acts as a membrane to keep de-icing salts from seeping into the reinforcement of the roadways and any supporting structures. However, problems exist with salt contamination of some crossbeams and pillars in concrete motorway viaducts, and it has recently been an- nounced on behalf of the U.K. Department of Transport that trials of several methods will shortly take place on parts of a motorway viaduct in the Midlands (28).

It has been estimated that over the next twenty-five years many millions of square metres of reinforced concrete will be fitted with impressed current cathodic protection systems. This application looks certain to become a significant new outlet for both noble metals and for refractory oxide base metals, principally titanium.

References I D. R. Lankard, Muter. Perform., 1976, 15, 24 2 M. Pourbaix, “Atlas d’Equilibres Electrochimi-

ques”, Gauthier-Vilars, Paris, 1963 3 U. R. Evans, “Metallic Corrosion, Passivity and

Protection”, Edward Arnold and Co., 1945 4 A. F. Baker, Paper No. 3,.Seminaron “Corrosion

in Concrete-Monitoring, Surveying and Control by Cathodic Protection”, organised by GCC, London Press Centre, 13 May 1986

5 J. E. Slater, D. R. Lankard, and P. J. Moreland, Muter. Perform., 1976, 15, (II), 21

6 References prior to 1985 can be found in Metals Information Bibliography Series 1985, “Corro- sion in Reinforced Concrete and Reinforcing Bars”, published by The Institute of Metals, London, and The American Society for Metals, Ohio. This lists several hundred references

7 K. Kendell, Ind. Corns., 1985, 3, (I) , 17 8 J. W. Figg, Corrosion, 1980, 5, 34 9 R. D. Browne, Paper 9, Second Int. Conf. on

“Maintenance of Maritine and Offshore Struc- tures”, 19-20 Feb. 1986, Inst. of Civil Engineers, London

10 N. J. M. Wilkins, “Cathodic Protection of Con- crete Structures”, Conference proceedings, “Cathodic Protection: Theory and Practice”, Ellis Horward Ltd., pp. 172-182

11 A. P. Crane, “Corrosion of Reinforcement in Concrete Construction”, Ellis Horward Ltd., England, 1983

12 J. E. Slater, “Corrosion of Metals in Association with Concrete”, ASTM Publication, Philadelphia, 1983

1 3 “Cathodic Protection of Reinforced Concrete Bridge Decks”, San Antonio, Texas, 12-13 Feb. 1985, National Association of Corrosion Engineers, 1985

14 J.P.Cotton, Platinum Metals Rev., 1958,2, (2), 45 15 L. L. Shreir, Platinum Metals Rev., 1977,z1, (4),

16 P. C. S. Hayfield, Platinum Metals Rev., 1983,

17 P. Nicholson, Paper 42, NACE Meeting, Corro-

18 J. S. Tinnea, Paper 181, NACE Meeting, Corro-

110; ibid., 1978, zz, (I) , 14

27, (I), 2

sion/81, Toronto

sion/83, Anaheim, California


19 W. R. Schutt, Paper 267, “Steel-in-Concrete Cathodic Protection, Results of a 10-Year Ex- perience”, NACE Meeting, Corrosion/85, 2,100,290; 1982 Boston, Massachusetts

25 R. F. Stratful, op. c i t . , Ref. 13, p. 66 26 European Appl. 147,977& 1985, British Patent

27 Proposed NACE Standard, Recommended Prac- tice for “Cathodic Protection of Reinforcing Steel in Concrete Structures”, 1986

28 U.K. Dept of Transport Press Notice, “Trial to Prevent Steel Corrosion on Midland Link Motor- ways to Start Soon”, 10 July 1986, Andy Hopkin- son, central office of Information, Birmingham

20 British Patent 1,457,511; 1973 21 British Appl . 2,140,456A; 1984 22 British Patent 1,351,741; 1970 23 European Patent 47,595; 1982 24 European Appl . 186,334A; 1986

Some Platinum Group Metals Cluster Catalysts Contribution of Clusters Physics to Materials Science and Technology

EDITED BY J . DAVENAS AND P. M. RABEITE, Martinus Nijhoff, Dordrecht, 1986, 646 pages, Dfl. 250,000/L69.25

Clusters and small particles have a large area to volume ratio and can therefore be considered as an intermediate state of matter at the interface between atomic or molecular chemistry and the physics of condensed matter. Dis- cussion at the NATO Advanced Study Institute held in France in 1982, where the papers in this book were given, centred on the critical size at which the change to bulk properties occurs.

The book includes a chapter on catalysis by molecular clusters and many of the examples given contain platinum group metal systems. Following a description of the reactivity of molecular clusters, the reactions catalysed by these systems are described. The rhodium and ruthenium catalysed synthesis of ethylene glycol from carbon monoxide and hydrogen under high pressure conditions has been studied in detail by workers at Union Carbide and has been shown to involve anionic clusters such as [Rh,(CO),,I-, and [HRu,(CO),,I- and Ru(CO),I,-; but other examples showing unambiguous catalysis by clusters are still rare. Two examples of homogeneous catalysis given are the isomerisation of olefins catalysed by H,Os,(CO),, and catalysis of the water gas shift reaction by Ru (CO) I 2 . Olefin hydrogenation has been shown to be catalysed by silica supported HOs , (CO) I ,, and the water gas shift reaction is catalysed by Rh,(CO) I on alumina.

Molecular clusters can be used as starting materials for the preparation of heterogeneous catalysts, and for ruthenium systems cluster derived catalysts display enhanced activity for the hydrogenation of straight chain aliphatic hydrocarbons. The increased activity super- ficially correlates with the smaller metal crystallite sizes reproducibly obtained with metal cluster compounds as catalyst precursors.

The study of the organometallic chemistry of

surfaces could prove to be a significant area for future investigations. For example, the oxidative addition of hydrogen onto a co- ordinately unsaturated rhodium atom on the surface of alumina has been described.

The book gives many examples of the surface characterisation of supported platinum metals catalysts and, for example, links product selectivity in catalysis to platinum particle size in platinum on alumina catalysts produced by the evaporation of a range of platinum film thicknesses followed by various treatments in hydrogen and oxygen. There are many surface methods available for the characterisation of metal supported catalysts and examples of the use of ESCA, EXAFS, EELS and other techniques are given throughout the book.

Cluster science has relevance to a large number of solid state sciences including metallurgy, magnetism, and defects in solids and alloys, in addition to inorganic chemistry and catalysis. Interrelating results from all these fields is still in its infancy, but this book has helped to focus attention on the value of considering the relevance of cluster phenomena to them all. D.T.T.

Commodity Meeting on Platinum The Institution of Mining and Metallurgy is

to hold its Annual Commodity Meeting on December 4th, 1986 at The Geological Society, Burlington House, London. The programme will include presentations on platinum as a strategic metal, exploration targets and guidelines, the UG2 platinum reef, processing of platinum metals, developments in the platinum market, trends in industrial applications, and its use in the control of gaseous environmental pollutants.

Platinum Metals Rev. , 1986, 30, (4) 166

Striving to Advance Platinum Technology INDUSTRY SEEKS TO ENCOURAGE ACADEMIC PROGRESS

During the latter part of the eighteenth century the only source of platinum was New Granada, a region located in the north-west of South America, and history records that the Spanish authorities donated quite substantial amounts of the metal to individuals and scientific institutes throughout Europe in order that its properties could be established and uses found. In due course applications were found for the quite remarkable properties of platinum by a select group of manufacturers, including the firm that became Johnson Matthey. For many years from about 1870 onwards George Matthey, a member of the Chemical Society and the Royal Institution and later a Fellow of the Royal Society, encouraged his large circle of scientific friends by providing them with samples of platinum and the other metals of the platinum group for the investigation of their properties and in the search for further applications. This policy of co-operation with the

scientific world continues to this day and the University Loans Scheme operated by Johnson Matthey has enabled many scientists worldwide to obtain platinum metal materials for their researches. This co-operative approach will be taken a step further at the Barclays Techmart exhibition, to be held 11th to 14th November 1986 at the National Exhibi- tion Centre, in Birmingham, England, where Johnson Matthey is participating for the first time. This exhibition will provide an ideal forum for academia to discuss scientific problems related to platinum and its applications, or ideas for collaborative ventures in new platinum metal technology. To illustrate the scope for new ideas, examples from the broad spectrum of current applications of platinum will be displayed, together with the scientific rationale underlying their use. Although the chosen theme “Plati- num - The Catalyst for Change” is metaphorical, catalysts themselves offer a

major research and development oppor- tunity to advance further their industrial application in chemical processes, pollution control and energy generation systems, such as fuel cells. Work is required to correlate the catalytic properties of platinum-containing materials with their solid state chemical and physical characteristics. Fundamental materials studies are also essential for future electronic applications. High- temperature and catalytic applications which illustrate the cost-effectiveness of platinum in industry will be displayed, together with biomedical uses such as in Carboplatin, the second-generation platinum-based anti-cancer drug launch- ed earlier this year. R.J.S.

Fuel cell development will be the central feature of the Johnson Matthey display. The 500W prototype shown here has been deaigned as a portable aource of electricity for use in remote locations for charging batteries or for powering communications equipment. The hydrogen fuel is supplied from a lightweight cylinder, but a portable methanol-fuelled generator may be used

Platinum Metals Rev., 1986, 30, (4), 167 167

High Pressure Ammonia Oxidation AN EXPERIMENTAL PLANT FOR EVALUATING PLATINUM CATALYST SYSTEMS FOR THE NITRIC ACID INDUSTRY

By K. G. Gough and B. L. Wibberley Johnson Matthey Metals Limited

The principles of the design and operation of a new variable high pressure, large diameter experimental ammonia oxidation test facility built by Johnson Matthey Metals Limited are described. The layout and arrangement of the plant are illustrated in some detail and examples of its use with platinum catalysts are given. The design of the plant is such that the operating conditions of any current, or likelyfuture, commercial undertaking can be reproduced.

The nitrogen cycle established by the natural world which enables plants to grow is extensively supplemented nowadays by man-made fertilisers. The tangible benefits of additional fertilisers are high crop yields and the delay of Thos. Malthus’s gloomy prediction of a world with a population too big to feed. Since early times attempts to rejuvenate the soil’s supply of essential minerals have been made, but it was not until the end of the nineteenth century, at the peak of the great European Chemical Industry era, that bulk production of manufactured nitrates was established. In 1908 Ostwald and Brauer first operated the platinum catalysed ammonia oxidation process on a commercial scale in Germany, the method which eventually rendered other inorganic methods of nitrate production obsolete. Their work has been reported in this journal previously (I). Development of the process was spurred on during the following few years due to the war- time blockade of the Chilean nitrate route which interrupted the supply of nitrates for explosives and fertilisers. Since that time the industry has grown to become one of the largest tonnage output processes in the world, estimated to be approximately 60 x 106 tonnes of nitrogen per year (2).

At the heart of the modern process is a chemical reactor, containing a platinum based catalyst and associated catchment gauzes,

which allows the ammonia oxidation process to take place readily at an efficient and economic rate. About 70 per cent of the nitric acid produced is used in the manufacture of nitrate fertilisers; the remainder being utilised in the production of nitrogen containing products, such as explosives, plastics and dyestuffs. The reaction is considered by chemists to be a three- stage process involving initially the “burning of ammonia gas with air” over the platinum based catalyst to form nitric oxide, followed by the oxidation and the absorption of this gas in water to form nitric acid. The oxidation reaction with air is complex but can be summarised in the equation:

4NH, + 50, - 4NO + 6H,O + 906.7 kJ This gaseous reaction, which gives acceptable yields at temperatures between 750 and 95Ooc, has been found to be sensitive to a number of variables. Other than temperature and pressure, product yield is influenced by the nature and distribution of the catalyst material and the cleanliness and throughput rate of the reacting gases.

To aid the study of such phenomena an experimental plant representative of today’s high pressure, high output manufacturing process has been constructed at Wembley. This plant is superior to installations reported on previously (3) because of its larger catalyst reactor size and its higher operational pressure range. A view of


Fig. 1 The exterior portions of the experimental plant, showing in the bottom left hand comer the bunded ammonia cylinder, with exterior control gear and nitrogen gas store to the centre and right, respectively. The shelter behind the blue cooling tower houses the air compreeeor, and the large tank in the centre receives acid from the absorption towers. The left hand and central towers extending above the adjacent laboratory handle the acidabsorption stages, the third being the tail gas scrubber

the external features of the new plant is shown above in Figure I, and a diagrammatic layout of the major components is given in Figure 2.

Plant Design The design is modelled on conventional nitric

acid manufacturing plant, with the exception of the reactor section which is specifically made to be adaptable to suit experimental variation, including simulation of different commercial operations.

The operational pressure range is between I and 12 bar (15 to 180 psig), with gas preheat capability of between ambient and 375OC. Various catalyst diameters up to 100 mm (4 in) are allowed for with an ability for a “deep bed” arrangement up to 150 mm (6 in) to be accom- modated. Gas flow is upwards with gauze ammonia loadings of up to 200 TPD (tonnes per day per mz catalyst projected area) in the

high pressure range, and continuous runs of at least seven days can be made. Longer runs are possible if allowance is made to refill from bulk ammonia storage located on site. The preheater and reactor sections, shown in Figure 3, are housed separately in a ventilated room adjacent to a laboratory area where the system control panel is located; a part can be seen in Figure 4. Controllers, readouts and sample ports sited on the panel allow catalyst activity measurements to be made comfortably and safely in the laboratory. Detailed descriptions of the various parts of the plant are as follows.

Ammonia and Air Supply Ammonia for the plant is stored in a thick

rolled steel shell ammonia cylinder which has a capacity of 1400 kg, sufficient to run the plant continuously for a week at maximum throughput. In order to run the plant at pressures


n

N~TROGEN

Reactor

Pressure Cylinder

L A I R

Fig. 2 Here the flow of gases and liquors through the major items of plant are indicated. Filtered compressed air is metered into the preheater before being mixed with vaporised ammonia fed from the high pressure cylinder. The mixed feedstock then enters the reactor where it is converted over the platinum-based catalyst mainly into nitric acid and water. The gaseous products are then cooled and diluted with air prior to being circulated through the absorption towers to generate nitric acid. At this stage the acid is taken to storage and the tail gas circulated through the scrubber to remove traces of acid gas

greater than the vapour pressure of ammonia and to eliminate fluctuations in flow caused by changes in ambient temperature, the cylinder is pressurised with nitrogen to an operating pressure of about 15 bar (225 psig). During use the cylinder pressure is maintained automatically by means of a pressure controlled solenoid valve on the nitrogen supply line. The cylinder is charged with ammonia from a 20 tonne bulk ammonia storage facility located on site.

For health and safety reasons the ammonia cylinder is located within a high retaining wall, with all apparatus controlled from a panel positioned outside.

The content of the cylinder is measured using a load cell situated underneath. The display for this is located on the control panel along with gauges showing supply line pressure, cylinder pressure and nitrogen pressure. The load cell is also connected to alarms in the control room to warn when filling is required and to signal com-

pletion of the filling operation. The ammonia supply is transferred to the reactor site in liquid form, where it is vaporised by means of a standard ammonia boiler.

Air for the plant is taken from the atmosphere and compressed using a two-stage, water cooled, high pressure compressor. This supplies air at 40 bar (600 psig) to a large air reser- voir, to which is fitted a pressure switch in order to maintain a pressure of 30 to 33 bar (450 to 500 psig).

The air is then passed through a filter to remove any foreign material before being reduced to’the operating pressure by means of a two-stage pressure reduction device. The high initial pressure and the two-stage reduction are employed so that changes in flow due to pressure variation during air compressor cycling are minimised. The ammonia supply, maintained at a temperature of about 150Oc after the vaporiser, is also passed through a


Fig. 3 The insulated gas preheater, mixer and reactor sections are housed inside, adjacent to the analytical laboratory. Meters and check valves are located under the insulated sections while the controllers and sample ports are mounted at the rear of the blue coloured control panel alongside the analysis area

filter and a pressure regulator to reduce its pressure to the desired operating pressure.

Flow Control System The flowrates and the ratio of the two re-

actants to the reaction chamber are measured and controlled by means of thermal mass-flow meters located on each line and linked to controllers and flow control valves.

The signal from the air flow meter provides the input to the primary control. The flow-ratio controller provides the set-point signal and receives a process variable signal from the ammonia mass-flow meter. The output is fed to a flow control valve on the ammonia feed line downstream of the flow meter, so that the selected flow-ratio is automatically achieved. The result of this is a dynamic equilibrium of the ammonia and air flows which can thus operate within close limits. This feature is particularly important when the plant is being used experimentally and operating close to the explo- sion limit of ammonia-air mixtures. Provision eists within the system for manual flow con-

trol, and in practice the plant is normally started up in this mode. This improved flow control system enables a

wide range of reactant flowrates to be established quickly and reproducibly and, most

Fig. 4 Here a gaseous sample is being with- drawn from cae of the valved outlets sited on the main control panel. The whole expermental operation is monitored from this laboratory


Simulation of Commercial Nitric Acid Plants

Pressure, atmospheres Preheat temperature, O C

Ammonia, vol per cent Ammonia loading, tonnes/

Number of gauzes Gauze outlet temperature, O C

Average conversion efficiency,

Conversion efficiency obtained

m2/day

per cent

on pilot plant, per cent

Medium/high pressure plant

7.2

10.8

36 10

940

230

92-94

92.2

importantly, offers the facility to maintain them within close limits over extended campaigns.

Reactor Assembly The air is preheated by'passing it through

two electrically heated sections arranged sequentially, each containing two coiled heating elements. The ammonia is introduced into the air stream after this point by means of a specialised flange designed to create a homogeneous ammonia-air gas mix. Adjacent to this point is a section containing a bursting-disc holder fitted with a in reverse type, FTFE coated, nickel disc. The gas stream then passes upwards into the reactor section, illustrated in Figure 3, which has been designed so that the catalyst may be changed between campaigns without difficulty. Catalyst holders able to accommodate gauzes of between 25 mm (I in) and 100 mm (4 in) diameter and cartridge type catalyst elements up to I 50 mm (6 in) deep can be used within the reactor.

Thermocouples to monitor the process line temperature, together with pressure switches are located at various points along the reactor and feed lines. These are connected to various recording devices and to alarm sensors which cause the plant to shut itself down in the event of a potentially hazardous situation arising. Thermocouples are also present on either side of the catalyst bed, as are sampling ports so that analysis of the reactant and product gases can

Medium pressure plant

5.2

10.5

16 10

890

150

93-95

93.5

be carried out. These sampling lines are also connected to a differential pressure transducer so enabling the pressure drop across the catalyst bed to be accurately determined.

The pressure drop across the catalyst and the catchment gauzes is an important factor to be considered both from a chemical and an economic viewpoint. In the former case the residence time and reaction path of various reactant and product species is affected, and in the latter case the energy balance is changed. During a production campaign there is a natural increase in pressure drop due to both a metallurgical material restructuring effect and the physical clogging of the gauzes which results from material migration by a catalytic vaporisation-deposition reaction.

Energy balance becomes most important in high pressure plants where the efficiency of heat recovery may be lowered to the detriment of the economics of the whole plant. Figure 4 shows part of the main control panel which contains the pressure drop display and also the sampling section.

Cooling and Absorption Systems The gases leaving the reactor, at tem-

peratures as high as 96ooC, are passed through a specially designed tubular heat exchanger. This consists of an Inconel 825 tube within a stainless steel outer tube fitted with bellows, enabling it to increase in length to take up the

Platinum Merals Rev., 1986, 30, (4) 172

expansion of the Inconel tube. Recirculating water continuously passes through this heat exchanger enabling the product gas to be cooled to below 20o0C, after which it is passed through the main flow control and pressure let- down valve. The gas, at about I W O C and just above atmospheric pressure, enters the low pressure oxidation and absorption stages.

Air is added to cool the gas further and promote the oxidation of nitric oxide to nitrogen dioxide. Afterwards the gas enters the first of three, 300 mm (12 in) diameter absorption towers each containing three 1500 mm ( 5 ft) beds of standard tower packings. Two towers are constructed from 316L stainless steel and handle the acid gas absorption stages. The gas in the first tower is scrubbed by dilute nitric acid produced in the second; giving approximately 30 weight per cent nitric acid which is pumped to a 3500 gallon stainless steel storage vessel before being transferred for use within Johnson Matthey. Water is added to the second tower to maintain the liquid level in the scrub- bing system, so producing acid of approximately 10 weight per cent.

The third tower is of similar design to the first two but is constructed from polypropy- lene. Sodium hydroxide solution is pumped through this tower on a closed circuit system to neutralise any nitrogen oxides remaining in the gas stream before emission to the atmosphere. A demister trap is fitted to the outlet to prevent any sodium hydroxide solution being carried out with the exhaust gas.

Although the absorption processes in the towers are exothermic and favoured by low temperatures, it has only been found necessary to fit a heat exchanger to the recirculatory liquor passing around the first tower. This heat exchanger is water cooled and is fed from a self- contained recirculatory system through an air cooling tower, which also provides water for cooling the water of the plant cooling circuit.

Work Carried Out in the Plant An example of the capabilities of the

ammonia oxidation plant was demonstrated by a simulation of two commercial type operations

which use rhodium-platinum alloy gauze. The development of platinum group metal catalyst and catchment systems has been the subject of earlier articles in this journal (4-6). The plants modelled'here were a medium pressure and a medium-high pressure installation, each having ten catalyst gauzes woven from 0.076 mm diameter 10 per cent rhodium-platinum wire for a normal campaign. The trials on the test rig were run under the operating conditions of the commercial plants, except that a higher preheat temperature was used to compensate for the greater heat losses experienced on smaller diameter test rigs. These running conditions, together with the results obtained from the investigation, are shown in the Table.

The conversion efficiencies of ammonia to nitric oxide, measured on the pilot plant over 24 to 72 hour campaigns, were obtained by the Gailliard method (7). Within the limits of experimental error, they show close agreement with those normally found on commercial plants.

Other work has included an investigation of the mechanism of reconstruction of catalyst gauzes, reported in this journal recently (8).

A Tool for the Nitric Acid Industry These examples highlight an important use of

the ammonia oxidation test rig. It has also been extensively employed on new catalyst and catchment development as well as for product optimisation. It has become a valuable tool in the development of platinum metal based catalyst and catchment systems for the nitric acid industry.

References I L. B. Hunt, Platinum Metals Rev., 1958,z, (4), 129 2 United Nations Industrial Development Organiza-

tion, Vienna, Fertilizer Manual, 1980 3 J. A. Busby, A. G. Knapton and A. E. R. Budd,

Fertilizer Society, Proceedings, 1978, (169) 4 H. Connor, Platinum Metals Rev., 1967, 11, ( I ) , 2

5 H. Connor, Platinum MetalsRev., 1967,11, (2), 60 6 A. E. Heywood, Platinum Metals Rev. , 1982, 26,

7 D. P. Gailliard,J. Id. Eng. Chem., 1919, XI, 745 8 A. R. McCabe, G . D. W. Smith and A. S. Pratt,

Platinum Metals Rev., 1986, 30, (2), 54

( I ) , 28


Energy Storage and Transmission PLATINUM CATALYSES CHEMICAL CLOSED-LOOP SYSTEM

By N. Giordano, G. Cacciola and A. Parmaliana Institute C.N.R. for the Transformation and Storage of Energy, Messina, Italy

Increasingly the energy needs of society will have to be met from renewable resources. The use of these is limited at present by their location, the technologies available to harness them and the major problems associated with their storage. One possible solution to these difficulties has now been demonstrated, and is described here, while further development W L rk is continuing. Hydrogen produced by any convenient means is used as a medium for energy storage and transmission. Close to its production site the hydrogen is catalytically reacted with toluene to yield rnethylcyclohexane; this is transferred safely by pipeline or container to the point of energy requirement where it is catalytically dehydrogenated. The hydrogen released is then available for use in a wide variety of ways, while the toluene is returned to the source for further hydrogenation, and the cycle is repeated.

The use of hydrogen as a fuel is not a new idea, having been proposed by J. B. S. Haldane in 1923 (I); however, the term “Hydrogen Economy” is more recent, being used first by John O’M. Bockris in 1971 (2). This concept relates to the possibility of using hydrogen as an energy medium. Appropriate technologies, including electrolysis, photovoltaic and thermochemical conversion are employed to produce hydrogen which is then used in conventional ways to produce thermal or electrical energy. It is evident that exploitation of renewable energy sources such as solar, wind or hydroelectric power by these means would be very dependent upon the location of the sources and the time they were available for energy generation. Con- sider, for instance, the climatological and geographical dependence of solar energy, the fluctuating character of the winds and the seasonal variations in the rainfall upon which hydroelectricity depends.

A prerequisite for these energy sources to be exploited successfully is the solution to the problems of hydrogen storage and transmission. An additional but no less important factor would be the availability of cheap land.

The ambitious goal of harvesting these dilute energy resources will require vast areas of desert where solar energy could be converted by thermal or photovoltaic means. Similarly the development of the huge unused sources of hydroelectric power would also require large areas for water collection and storage. These are available, but mostly in remote regions of the world, such as central Africa, central South America and northern North America; all at great distances from existing major energy users.

Although these problems belong to a future in which renewable energy sources will have to play an ever increasing role, finding more effective means for both storing and transmitting hydrogen could have important implications for everyday life. A solution to these problems would, in fact, have a bearing upon the many applications where hydrogen is currently used. At present transmission in liquid form may be restricted by hydrogen embrittlement which affects steel containment vessels and pipelines. As safety and energy density are paramount for any hydrogen utilisation programme, it is not surprising that great efforts are being made to

Plaiinum Metals Rev., 1986, 30, (4), 174-182 174

The r ma1 energy - input - €$ -6.C h-q Thermal

= n e w output

Trans missionlstorage

Fig. 1 In the “chemical heat pipe” system for energy storage, A is catalytically dehydrogenated to B and C with any available heat source. This energy is then transmitted to the user where the original heat is released by catalytic recombination between B and C. A is formed and is returned to the start of the cycle. For the reaction methylcyclohexane = toluene and hydrogen, A is methylcyclohexane, B is toluene and C is hydrogen

find alternatives to the presently available methods of storage and transmission, which are as a compressed gas in pressurised vessels or as a liquid in cryogenic containers. Recently the preferred approaches have involved the development of hundreds of metal alloys for possible use as hydrogen absorbing materials, and further investigations of cryogenic storage in the presence of hydrogen absorbing materials. However, while these could solve the problem of storage, it was only in the 1970s that the search for more convenient means of transmission achieved prominence. Liquid hydro-

genated molecules such as methyl alcohol or ammonia were first considered, but these were soon abandoned because of the difficulties associated with the gaseous nature of the con- stituents if they were to be used in closed-loop systems. The use of methylcyclohexane (MCH) as a liquid carrier of hydrogen to be used for automotive purposes was first reported by Sultan and Shaw (3). Later this concept was adapted for storing and transferring energy by Vakil (4, 5). His “chemical heat pipe” (CHP) concept involved the (de)hydrogenation of cyclohexane and methylcyclohexane and this

1 I 1 L _ _ _ _ _ _ _ _ _ _ - - - - _ _ - _ - J

Fig. 2 An alternative view of the “chemical heat pipe” is as a hydrogen storage medium. Here toluene is catalytically hydrogenated at H, liberating stored energy. The methylcyclohexane (A) produced is transmitted to the user, a t D, where it is catalytically dehydrogenated. The liberated hydrogen can then be utilised, possibly in a fuel cell. The toluene (B) formed is then returned to the start of the cycle

Platinum Metals Rev . , 1986, 30, (4) 175

1O’L PETROLEUM

METHANE ILiquidl

HYDROGEN IHydrldel

HYDROGEN ILiquidl 0 HYDROGEN I M T H I 10-

BATTERY lProiectedl

THERMAL ENERGY IN M T H

CHEMICAL 10’-

LEAD ACID BATTERY LATENT HEATS

HYDROGEN (Gas1 10’-

HYDROELECTRIC 1100 rn d r o p d

J l d

10’

HYDROGEN

PETROLEUM rd

HYDROGEN I M T H l

10’ HYDROGEN IHydridel

THhRMAL ENERGY I N M T H

CHEMICAL

1 oa LATENT HEATS

LEAD ACID BATTERY WATER ISonsible. AT Z 0 ” C l

10

Fig. 3 A comparison of the chemical energy storage media shows the relative - 1 position of methylcyclohexane

Whlkg

was said to be the most suitable “model” reaction in a mid-temperature range.

To distinguish between the two concepts, consider the equilibrium of the catalysed reaction:

T*

T2 methylcyclohexanekAH toluene + 3H2 (i)

where T,>TI In the CHP concept for energy storage and

transmission the process starts from the left, in Equation (i). Any available heat sources such as waste heat or solar energy are used to carry out the endothermic catalytic dehydrogenation reaction, to the right. The products formed are stored and/or transmitted to the location where the energy is required. Here the original heat is released by exothermic catalytic recombination, to the left. A conceptual scheme of this closed- loop cycle is shown as Figure I. In the former idea, which relates to the storage of hydrogen, the same closed cycle is repeated but the starting point is different, see Figure 2. It starts with the hydrogenation of toluene and the methylcyclohexane formed is transmitted to the end-user, where it is decomposed. The

hydrogen released is consumed by any conventional means, or preferably in a fuel cell, and the toluene is sent back to the source for recycling.

Methylcyclohexane-Toluene- Hydrogen

Initial outlines of both concepts have been expanded in this Institute and elsewhere, to include engineering, catalytic and kinetic aspects, and techno-economic evaluation (6-23). Before going into details the main features of the methylcyclohexane-toluene- hydrogen cycle (MTH) will be summarised. First, MTH ranks amongst the best of the chemical storage media, even though these are poor when compared with fossil fuels; this is demonstrated in Figure 3. The ability to collect dilute quantities of energy is however a characteristic feature of chemical storage, in contrast to the depletive consumption of fossil fuels. With an energy storage capacity of 0.63 kWhkg of methylcyclohexane (the heat of the hydrogenation reaction), 18 round trips of the methylcyclohexane-toluene-hydrogen cycle


store energy equivalent to I litre of oil. For hydrogen storage the MTH system offers definite advantages (energy density) over conventional systems, as shown by the data in Table I, and possesses the additional unique benefits of indefinite storage, ease of handling and transmission even over long distances. Furthermore the melting points of the components allow the system to be used under arctic conditions.

For these two closed-loop cycles to be cost effective, very stringent requirements have to be met. First the catalysts must possess long- life, high activity and the ability to catalyse both the dehydrogenation and the hydrogenation reactions completely, unhindered by even traces of by-products. In undertaking experimental work at this Institute it was accepted that even though the isolated (de)hydrogenation of cyclohexane and of methylcyclohexane are not used commercially they do form part of a series of reactions which are used industrially on a large scale for the catalytic reforming of naphthas to yield high

Density, grams of hydrogen

per litre

Octane reformates. These reactions are catalysed by noble metals which therefore were also considered for our investigations. At the start, interest was focused on the cyclohexane- benzene cycle as a “probe” reaction. Although many platinum-based catalyst formulations were tested only a few attained IOO per cent selectivity, which was seen as a goal since even trace amounts of methylcyclopentane seriously affect the number of cycles necessary for a closed-loop system to be realistic. The superior performance attained over proprietary catalysts based upon honeycomb supported platinum encouraged extensive work at this Institute on all their inherent catalytic, structural and kinetic aspects. High turnover numbers comparable to those of conventional catalysts were found, with the added benefit of 100 per cent selectivities for both the forward and the reverse reactions. Typical conversion plots of conversion against contact time, W E (where W is the weight of the catalyst and F the flow rate of the reactant), are shown in Figures 4, 5 and 6; the data being obtained as part of a

Theoretical weight per cent, grams of hydrogen per

gram of saturated compound

Table I

Comparison of Characteristic Properties of Hydrogen Storage Systems

Gaseous hydrogen P = l bar I P=200 bar

Liquid hydrogen

Cryogenic storage with I adsorbing material

Metal hydrides TiH, I FeTiH,

Reversible organic reaction C,H, +3 H, e C,H,, I C,H, +3 H, $ C,H,

0.09 1 100 18 100

70 I 100

56 47.4

7.19 6.16

Mass of non- saturated compoun

needed to store 1 kg of hydrogen,

kg

20

25 77

12.9 15.2


r _ _ . . . , . . . ~ , . CONTACT TIME (W/F),ghlrnol

100 500 1000

Fig. 4 The conversion of cyclohexane to benzene versus contact times at various temperatures, when the volume ratio of the reaction mixture N, : CH is 5, N, serving as a carrier for the cyclohexane

- zoo-c

- 2M'C

2BO.C

.300'C

1 0 0 ' 500 ' 'rob0 1500 CONTACT TIME (W/F).ph/mol

- zoo-c

- 2M'C

2BO.C

.300'C

1 0 0 ' 500 ' 'rob0 1500 CONTACT TIME (W/F).ph/mol

Fig. 5 The conversion of benzene to cyclohexane versus contact times at various temperatures, when the volume ratio of the reaction mixture H, : benzene is three

275.C 300.C :too.

d 0

U 250.C

80. 225'C &

z 0 60, In U

z 40. 200.C

0.

I 200 4 0 0 600 800 1000 1260

CONTACT TIME (WIF), ghlrnol

Fig. 6 The conversion of methylcyclohexane to toluene versus contact time at various temperatures, when the volume ratio of the reaction mixture N, : MCH is five

continuing programme aimed at determining all parameters necessary for the scale-up, construction and testing of a pilot plant equivalent to a thermal power source of 6 kW (7). The geometry of the honeycomb monolith proved to be advantageous, the low pressure drop through it reducing the energy needed for pumping. Based upon extensive catalytic and kinetic information, some typical flow-sheets have been examined, and the one shown here as Figure 7 appears to offer the best compromise.

Relying upon a theoretical energy density of 0.68 kWhkg of cyclohexane-for the chemical heat pipe concept of energy storage-and 2.4 kWhkg of cyclohexane-for hydrogen storage-flow-sheets of this type have been adapted conceptually by us to fit the purposes of an ideal heat-storage plant of 1000 kW (7), or for the storage and transmission of 200 MW as hydrogen over a distance of 160 km (9), or the transmission of IO,OOO MW electrical power as compared with the equivalent hydrogen energy as MTH, over distances of thousands of kilometres (I 2).

Supported Platinum Catalysts Although details are not given here, we want

to emphasise some essential points of the proposed processes. First, beyond any doubt the use of correctly tailored platinum catalysts is a

Fig. 7 This flow-sheet of a hydrogen storage andlor transmission system u s i n g a reversible chemical reaction has been selected as the best compromise R, hydrogenation reactor R, dehydrogenation reactor S, liquid gas separator S, counter flow heat exchanger H, hydrogen tank


c

5 0.06. y i ,

U 0.04. ul 9 ' 0, 0.02. a ln

1000 2 0 0 0 3000 TIME STORED, hours 1000 2 0 0 0 3000 TIME STORED, hours TIME STORED, hours

Fig. 8 The variation of storage costs per unit of stored energy as a function of the time stored (a) for short time storage, (b) for weekly storage, (c) for seasonal storage LH = liquid hydrogen CA = cryoadsorher storage MH = metal hydride storage (FeTi) LP = low pressure storage (12 bars) CB1 = cyclohexanehenzene process CB2 = cyclohexanehenzene process

without recovering the heat of hydrogenation

i I \ 8 0.04

c 0 2 c01

i - L P 0.02 * I

I 1000 2000 300( TIME STORED. hours

prerequisite, for they alone assure no losses of the recycled reactants and products. As the catalyst represents the heart of the process, further improvements to it are necessary, particularly for the MTH cycle where, at least under the most severe high temperature conditions of the dehydrogenation step, it suffers from a number of weaknesses, the most critical of which is a tendency to coking. Progress on this is likely to result from parallel work being

carried out on the catalytic reforming of naphthas, by which means IO* tondyear are processed using a platinum catalyst to increase the octane number. As deactivation by coking is the main difficulty we have recently focused our attention on the role of chlorine, which appears to be the key to this problem (23). If the limitation imposed by coking could be removed there is no doubt that the MTH cycle would have a great future. The way forward has

r------- i

L--- - - -J

Fig. 9 Flow chart of an alternative method for transporting large amounts of electrical energy from a hydroelectric plant, stored as hydrogen in methylcyclohexane, over large distances to the user

~ ~~


- E Q UI 1

I m 0

c

C

C Q 0)

-0 z r

0 UI 0 4- UI

.-

2

?! c

n U

0 C 3 0

.- - 4-

E a -

c' m ? Q

-0 1 m T Y

-0 ?! x

6 EJ= i=

2 0

II I

2 X Ln Ln

~

- e N m

W

P

0 m

already been prepared. A 17-ton truck with an engine producing I 50 kW of mechanical power has been built and run successfully (21); even though improvements to the platinum- rhenium/alumina catalyst are still seen as a goal, this trial has demonstrated the readiness of the MTH closed-loop cycle to serve present needs while at the same time it is being developed for the future.

The ability of the MTH concept to serve in a future hydrogen economy has already been demonstrated and work carried out at this Institute has contributed to this. Catalyst formulations for the forward and the reverse reactions have been disclosed, and an adiabatic- type reactor which reduces capital costs has been proposed (7); this is illustrated in Figure 7. Computer optimisation of the main operating conditions and full heat- and mass-balance evaluations (9) have been established, to serve as the guidelines for future projects.

Estimation of thermodynamic efficiencies, reactor volumes and the other engineering

Fig. 10 This plot of emciency of transmitted energy versus the distance travelled to the user shows that at distances greater than about 2000 km transmission of energy by the cyclohexane-benzene system is cheaper than transmission along overhead wires

E electricity G hydrogen transmitted by a gas

pipeline CIB hydrogen transmitted by a

cyclohexane-benzene system

Platinum Meruls Rev., 1986, 30, (4) 180

la) E

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ric p

ower

Ib

l Rat

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nerg

y re

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parameters-given in Table 11-all contribute to the background information required to turn this process into a successful energy or hydrogen storage package.

The reader is reminded that only the MTH cycle meets the requirements for both storage and transmission of hydrogen, other conventional means being unsatisfactory for transmission. Unique advantages include the unlimited duration of storage, an energy density that is higher than that of any other reversible system, while there is no need for insulated vessels or pipes. All these factors, plus the extremely low cost of the starting materials, combine to make the cost of hydrogen storage and transmission at least one order of magnitude lower than that of any conventional process. This is demonstrated by the data in Figure 8.

Towards a Hydrogen Economy Looking to the future, it is to be hoped that

these lower costs and other considerations, such as pollution control and energy conservation, will attract the attention of sections of our industrial society. Of all the renewable energy resources, hydroelectricity is perhaps the source that could benefit first from this new technology, as unexploited resources amount to

4 x 109 tons of petroleum equivalent (TEP) per year; one TEP being 1 0 7 kcal and I I .6 x 1 0 3

kWh. This amounts to about 60 per cent of the present world consumption of fossil-fuel energy! Taking this as an example we have anticipated conceptually that it would be cheaper to transmit hydrogen produced by electrolysis over a distance of 2000 km from the source by means of the methylcyclohexane- toluene-hydrogen cycle than it would be to transmit it through overhead wires as electricity. Figures 9 and 10 show this. The feasibility of producing and consuming hydrogen from this renewable source is not in doubt; the electrolysis of water is a mature technique and fuel cells are poised for com- mercialisation. It is therefore to be hoped that in time, as fossil fuels are increasingly depleted, the needs of the hydrogen economy will match the prospects offered by the MTH process, like a cure in search of a disease.

Acknowledgements Thanks are due to C.N.R. National Council of

Research Progetto Finalizzato Energetica and to Enea for financial support. The authors wish to express their appreciation to co-workers R. Di Leonardo, F. Frusteri, A. Mezzapica, E. Recupero, G. Restuccia and P. Tsiakaras for their contribution to the work reported.

References

I J. B. S. Haldane, in a lecture, “Daedalus, or Science of the Future”, at Cambridge, 4 February 1923

2 J. O’M. Bockris, Environment, 1971, 13, 51 3 0. Sultan and M. Shaw, “Study of Automotive

Storage of Hydrogen Using Recyclable Liquid Chemical Carriers”, TEC 75/003 ERDA, Ann Arbor, Michigan, 1975

4 H. B. Vakil, “Energy Storage and Transmission by Chemical Heat Pipe”, General Electric, Schenectady, N.Y., Technical Information Series No. 76CRD281, January 1977

5 H. B. Vakil and J. W. Flock, “Closed Loop Chemical Systems for Energy Storage and Trans- mission (Chemical Heat Pipe)”, ERDA Contract EY-76-C-02-2676, U.S. Dept. of Energy, February 1978

6 N. Giordano, “Thermodynamic Analysis of Solar Energy Storage through Thermochemical Rever- sible Reactions”, Comples, 18th Int. Conf. Solar Energy, New Prospects, Milan, 23-27 Sept. 1979

7 G. Cacciola, G. Resruccia and N. Giordano, Proc. Int. Conf. Energy Storage, Brighton, U.K., 29 April-I May 1981, I, pp. 73-89

8 G. Cacciola, Tecnol. Ckitn., 1981, I, (6), 56 9 G. Cacciola, N. Giordano and G. Restuccia, Int.

10 N. Giordano, G. Cacciola and A. Parmaliana, Indian J. Tecknol., 1983, 21, (9), 398

X I G. Cacciola and N. Ciordano, Proc. Fifth World Hydrogen Energy Conf., Toronto, 15-19 July

12 G. Cacciola, V. Recupero and N. Giordano, Int. 3. Hydrogen Energy, 1985, 10, (9, 325

13 A. Parmaliana, C. Crisafulli, R. Maggiore, J. C. J. Bart and N. Giordano, React. Kinet. Catal. Lett., 1981, 18, (3-41, 29s

14 A. Parmaliana, A. Mezzapica, C. Crisafulli, S. Galvagno, R. Maggiore and N. Giordano, React. Kinet. Catal. Lett., 1982, 19, (1-2), 155

1 5 A. Parmaliana, M. El Sawi, G. Mento, U. Fedele and N. Giordano, Appl. Catal., 1983, 7 , 221

3. Hydrogen E w w , 1984, 9, (9, 4x1

19843 3, PP. 1232-1251


16 A. Parmaliana, M. El Sawi, U. Fedele, G. Gior- dano, F. Frusteri, G. Mento and N. Giordano, Appl. Catal., 1984, 12, 49

17 M. El Sawi, F. Frusteri, A. Parmaliana and N. Giordano, 3. Chem. Technol. Biotechnol., 1985, 36, 122

18 A. Parmaliana, 0. S. Alekseev, G. A. Nesterov, Yu. A. Ryndin and N. Giordano, React. Kinet. Catal. Lett., 1986, 31, (2), in press

19 G. Moleti, R. Quagliata and G. Cacciola, “Studio di Fattibilita di Sisterni di Accumulo per Impianti

20 F. Ippolito, “L’Energia” da L’Energia: Fonti e Produzione-Letture da Le Scienze, Milano, 1976, PP. 13-25

21 M. Taube, D. Rippin, W. Knecht, D. Hakimifard, B. Milisavljevic and N. Gruenen- felder, Int. 3. Hydrogen Enera, 1985, 10, (9), 595

22 A. Touzani, D. Klvana and G. Belanger, Int. J . Hydrogen Enera, 1984, 9, (10, 929

23 A. Parmaliana, F. Frusteri, A. Mezzapica and N. Giordano, “Coking on Pt/Honeycomb Reforming Catalyst: Effect of Surface Acidity”, J. Catal.,

Eolici”, Intern. Rep., CNR Inst., Messina, 1983 submitted

At the turn of the century platinum was used extensively in photography, but the popularity of the platinotype process declined prior to the First World War. Recently, however, the process has been revived, while early photographs have come to be recognised as valuable collector’s items. Among the most sought after are the platinotypes ofPeter HenryEmerson(1856-1936). Hisalbum “Life and Landscape of the Norfolk Broads” was illustrated with platinum prints, which demonstrated the wide tonal range that could be obtained with platinum. Another feature ofthe process was the permanency of the image, and today the condition of his platinotypes testifies to this.

Almost one hundred years after publication of this book, and f e years after his death, an exhibition of his work is taking place at the Sainsbury

Centre for Visual A r t s , University of East Anglia, Norwich, until 26th October 1986. The platinotypes that form part of this exhibition, which is sponsored by Norwich Union Insurance, could appeal especially to those who have previously regarded platinum solely as an industrial metal.

Later the display will move to the Royal Photographic Society, Bath (5th December 1986-17th January 1987), University of Warwick (21st February-21st March 1987), Impressions Gallery of Photography, York (27th April-yst May 1987), and the Walker Art Gallery, Liver- pool (7th August-20th September 1987).

The image reproduced here, from an Emerson in the Johnson Matthey Collection, is featured in the exhibition.


The Platinum Prints of Peter H. Emerson

Organometallic Chemistry of Palladium Palladium Reagents in Organic Syntheses, Best Synthetic Methods

BY RICHARD F. HECK, Academic Press, London and New York, 1985, 461 pages, L85iU.S. $99

This is one of a new series of books designed to provide working details of methods which can be applied to the synthesis of organic compounds by the practising organic chemist. The book is not comprehensive but it does include all of the palladium-promoted reactions reported in the literature up to 1983 which are relevant to organic synthesis. In all 509 references are given. In the Detailed Contents, the subject matter of each chapter is itemised, and this arrangement together with an index of compounds and methods enables topics of interest to be located readily.

The opening chapter provides details of the preparation of palladium reagents and also of the recovery of the metal, and it is particularly helpful that procedures are given for the preparation of representative complexes. It is noted that while the initial cost of palladium is high (although comparable with many other organic reagents) the metal can be readily recovered and is therefore reusable. Thus the use of stoichiometric rather than catalytic amounts of palladium can be viable in particular reactions.

A very wide range of organic transformations are catalysed by palladium species and a chapter is devoted to each of the following topics: double bond isomerisation; palladium- catalysed molecular rearrangements; palladium-catalysed oxidation of alkenes, alkynes, benzylic carbons, carbonyl compounds and alcohols; palladium-assisted substitution and elimination reactions at allylic carbons; palladium-assisted couplings of aryl, alkenyl, ally1 and alkyl derivatives; palladium- assisted dimerisations and oligomerisations of alkenes, dienes and alkynes; palladium-catalysed carbonylations and decarbonylations; palladium-promoted cyclopropanations, and catalytic reduction by hydrogen transfer and related reactions.

The book is well-laid out and the 172 tables neatly summarise a vast quantity of information. These tables indicate reaction conditions and yields and provide references for specific transformations and are therefore particularly useful as a working aid. It is helpful that the author, who has a wealth of experience in the area of the organic chemistry of palladium, offers opinions on the usefulness of palladium in specific reaction types. Examples include: “With a few exceptions palladium and its complexes are not good double bond isomerisation catalysts” and “Not only do many of these catalytic rearrangements (sic sigmatropic rearrangements) occur under much milder conditions with the metal catalyst . . . but the reactions often occur in significantly higher yield and in some cases gave different products’’. These comments are helpful in deciding the relative merits of a particular reaction pathway.

It would also, however, have been beneficial to refer the reader to the treatise by B. M. Trost and T. R. Verhoeven entitled “Organo- palladium Compounds in Organic Synthesis and in Catalysis”, to be found in Volume 8 of “Comprehensive Organometallic Chemistry” (editor G. Wilkinson) published in 1982 by Pergamon Press, as the two texts are com- plementary.

Since this series is directed at practising chemists and ideally should be found in organic chemical laboratories it would be advantageous if the publishers could bring out a paperback version at a reduced price. This would do much to ensure that the remarkable catalytic properties of palladium become more widely used for the synthesis of novel organic molecules, thus realising the author’s expressed desire to “help organic chemists to simplify many organic syntheses with a significant saving of time, effort, and energy”. M . J .H.R.

Platinum Metals Rev., 1986, 30, (4), 183 183

Sintering Aids in Powder Metallurgy THE ROLE OF THE PLATINUM METALS IN THE ACTIVATED SINTERING OF REFRACTORY METALS

By C. W. Corti Johnson Matthey Technology Centre

When a metallic powder is subjected to a suffkiently high pressure a certain amount of adhesion takes place between individual particles. If this compact i s then sintered the bond is improved by diflusion and intergranular grain growth. The earliest known platinum objects were fabricated by such a powder metallurgical process, and when European scientists first addressed the problem of manufacturing platinum bars they also used powder metallurgy to Overcome their inability to melt the metal. N o w powder metallurgical methods are widely used for fabricating a variety of materials, and this paper reviews studies made of the sintering of refractory metals when this process is promoted by the addition of a minor amount of a platinum group metal activator.

The manufacture of engineering metals and alloys in fabricated forms generally commences with the melting and casting of ingot material for subsequent shaping by mechanical techniques, such as forging, rolling and extrusion, although in many instances molten metal can be cast directly to a final shape. However, in the case of the refractory elements, such as tungsten, molybdenum and rhenium, their very high melting points (in excess of 2o0o0C), as well as their resistance to deformation, generally precludes the melting approach as a practical route to material and component manufacture. This has led to the development of processes in which consolidation of powder materials is achieved by sintering at temperatures below their melting points.

To promote and assist the sintering process, two techniques have been developed which involve the use of metallic sintering additives. These are known as Liquid Phase Sintering and Activated Sintering. In Liquid Phase Sintering the refractory metal powders are sintered in the presence of one or more metals-generally transition metals such as copper or iron-at temperatures above the melting point of the additive, so that sintering occurs in a molten

binder phase which may be present in substantial amounts, for example up to 40 per cent by weight.

In contrast, Activated Sintering is performed in the presence of small amounts of metal additives, again often transition metals, but in the solid state at temperatures below the melting point of the additive. Thus, as can be seen from Table I, Activated Sintering can be accom- plished at lower temperatures than Liquid Phase Sintering, although not necessarily so, depending on the particular metal additive used. In both cases, however, the temperatures employed are substantially lower than would otherwise be required if the refractory powders were sintered without additives. Kurtz, for example, showed in 1946 that 99 per cent dense tungsten parts could be achieved by sintering below 140o0C with less than I wt. per cent addition of nickel (I), whereas temperatures above 2800OC are required to achieve a comparable density in untreated tungsten powder.

Activated Sintering Since Vacek reported the enhancement of

sintering by additions of small quantities of transition metals to tungsten in 1959 (2 ) ,


Tabla I

Typical Sintering Temperatures for Activated Sintering and Liquid Phase Sintering of Refractory Metals

1550 1100 1460

‘ >1350

I Refractory

element

Molybdenum

Melting point,

OC

Tungsten carbide

‘The tungsten carbide-cobalt eutectic

3410

2610

-

Activated sintering

Additive

Nickel Palladium

Nickel Pal I ad i u m

-

temperature is 1 32OoC

making it possible to lower the sintering temperature substantially, a great deal of work has been carried out into the activated sintering of tungsten and other refractory metals, particularly with additions of Group VIII transition metals. Much of this work has involved the use of platinum group metals which have been shown to be very effective as sintering activators. This paper reviews the published work on the effect of the platinum group metals on the activated sintering of tungsten and other refractory metals, in particular on the kinetics and mechanisms of sintering. The properties and microstructure of the sintered materials are also examined. Finally, the scientific basis for the beneficial effect of the platinum group metals in the activated sintering of the refractory metals is examined in terms of current theories and phenomenological models.

Tungsten Much of the early work on the activated

sintering of tungsten was carried out by Brophy, Hayden and co-workers (3-7). Their initial work focused on the sintering of tungsten powder coated with nickel. They found that, on sintering at I IOOOC, the tungsten underwent rapid densification to more than 90 per cent theoretical density. Moreover, they found that the amount of nickel required to promote this accelerated sintering was roughly equivalent to a nickel coating thickness of about I atom monolayer (3). Nickel coatings thicker than this

Sintering temperature,

OC

1100 1100 1200 1200 -

Liquid phase sintering

Additive

Nickel Copper Nickel

Cobalt


OC

did not produce any further enhancement; indeed, there was a tendency for the sintering rate to decrease from the optimum. They also found that densification occurred in two stages, the second stage coinciding with the onset of grain growth in the tungsten (4).

In an attempt to clarify the mechanism of activated sintering, which they had earlier attributed to the activating metal acting as a carrier phase for the diffusion of tungsten to the interparticle “necks”, Hayden and Brophy examined the influence of ruthenium, rhodium, platinum and palladium additions on the kinetics of sintering in the temperature range 850 to IIOOOC (7).

As in their previous work, the platinum group metal sintering additives were added to the tungsten powder in the form of aqueous solutions of salts (chlorides and nitrates) in the requisite amount; this was dried at I~oOC and prereduced in hydrogen at 80o0C to form a metallic coating on the tungsten powder. Sintering was carried out under hydrogen.

For all the platinum group metals examined, Hayden and Brophy found that a minimum level of platinum group metal was required to promote full activation, see Figure I , as had been observed in the case of nickel, and that larger amounts did not produce any further enhancement. Interestingly, palladium was the most effective element; this is clearly illustrated in Figure 2 which shows the temperature dependence of shrinkage for each platinum


g o 0 0 1 l'o 2.0

0.002

310 4' AMOUNT OF ADDITIVE,weight per cent

Fig. 1 During the activated sintering of tungsten the linear shrinkage is dependent upon the activator, and the amount added; a minimum level b e i i required to promote full aetivation. Data from Hayden and Brophy (7).

Sintered for 1 hour Palladium, 95OOC Ruthenium, 1 100 O C Platinum, 1 100 O C Rhodium, l l O O ° C

0.1.

: 005.

2 0.02-

5 0.01.

- 4 W 0

z K -

group metal additive after sintering for I hour. Ruthenium was the least effective element. Significantly, the authors found that palladium was better than nickel in promoting densification. For example, the densities of samples sintered at 110o0C for 30 minutes and 16 hours were 93.5 and 99.5 per cent, respectively, in the case of palladium in tungsten compared to 92 and 98 per cent, respectively, for nickel in tungsten. Untreated tungsten would only be presintered at this temperature.

Analysis of the sintering kinetics in terms of the process controlling mechanism in their carrier phase model of activated sintering- which applies also to liquid phase sintering- showed that for all the platinum group metals examined, the sintering rate was not dependent upon composition, but was proportional to the cube root of time, except for rhodium in a low shrinkage regime. This time dependence was interpreted in terms of the diffusion controlled transport of tungsten in the interface between the tungsten and the platinum group metal

coating layer. In the case of rhodium there is a transition in the rate controlling process, from the dissolution of tungsten in the rhodium layer at low shrinkages to interface diffusion at large shrinkages. Table I1 summarises these results, the slope, S , being the time dependence of the sintering curves.

Also shown in Table I1 are the calculated activation energies for each platinum group metal additive. These lie in the range 86 to I 14 kcal/mol, which the authors believed to be comparable to the activation energy for tungsten grain boundary self-diffusion.

The effectiveness of the platinum metals and nickel in promoting enhanced sintering of tungsten were found to be in the order:

Pd > Ni > Rh > Pt > Ru The reason for the platinum group metals being such effective activators for the sintering of tungsten was not established in this work, although it was suggested that it may be linked to their relatively high (10 to 20 per cent) solubility for tungsten and their low solubility in tungsten.

Subsequently Hayden and Brophy extended their work on platinum group metal activators

Rhodium ,' ./' 50.005 (lWt.%),' +/

/

0.002i 1 .

800 900 * l o o 0 1100 TEMPERATURE C

Fig. 2 The dependence of linear shrinkage upon temperature during the activated sintering of tungsten. This shows that after sintering for 1 hour, palladium is the most effective activator (7)


Table I1

Summary of the Effect of Platinum Group Metal Additives on the Sintering of Tungsten (Data from References 7 and 3)

Additive

Palladium Ruthenium Platinum Rhodium (a)

Rhodium (bl

Nickel

Slope ’S’

0.33 0.39 0.33 0.5 0.33 0.5

Control of process

Diffusion Diffusion Diffusion Solution Diffusion Solution

Activation energy, kcal/mol

86 114 92 85 98 68

(a) Rhodium : low shrinkage regime Ibl Rhodium : high shrinkage regime

to the sintering of tungsten with iridium additions (8). In contrast to the other platinum metals, they found that iridium actually decreased the rate of densification of tungsten, the effect reaching a minimum value at about 2

wt. per cent iridium, larger additions having no further effect. The measured activation energy of 133 kcal/mol was close to that for volume self-diffusion of tungsten ( I 35 kcal/mol).

Further work on the activated sintering of tungsten by palladium and nickel additions was carried out by Toth and Lockington, who also found that there were optimum concentrations of both palladium and nickel for maximum densification during sintering at 10ooOC (9). Calculations showed these optimum concentrations to correspond approximately to a monolayer of the activating element on the tungsten surface, as also found earlier by Brophy, Shepherd and Wulff (3). Once again, palladium was found to be more effective than nickel, especially at and below a temperature of 95Ooc. Toth and Lockington found the time dependence of the densification to be 0.5 for both palladium and nickel, in contrast to the value of 0.33 for palladium found by Brophy (7). The apparent activation energies were lower, 62.5 kcal/mol compared to 86 kcal/mol for palladium and 50.6 kcal/mol as against 68 kcal/mol for nickel. Microprobe analysis of the fracture surfaces of sintered specimens showed segregation of the activating elements on grain boundary surfaces. The authors concluded that Brophy’s model for activated sintering was not

applicable; rather, they favoured a mechanism in which the surface diffusion of tungsten on the activator surface is the controlling step; both are shown schematically in Figure 3.

The influence of a wide range of transition metal additions, including all the platinum group metals, on the sintering of tungsten at temperatures between 1000 and 2000OC was studied by Samsonov and Jakowlev (10). They found, in agreement with earlier findings, that additions of Group VIII elements-including the platinum group metals-promoted densification of tungsten, with the exception of osmium which was neutral. Iridium had a small beneficial effect at the highest temperature studied, 2o0o0C, which is not inconsistent with the earlier work of Hayden and Brophy (8), since extrapolation of their Arrhenius plots predicts a transition from a detrimental to a beneficial effect at temperatures above about 14moC. The effectiveness of the platinum group metals in enhancing sintering was found to be in the order:

Ru < Rh < Pd and 0s < Ir < Pt

with the upper row of elements being superior to the lower row. This is shown in Table 111, which also gives the measured values of compressive strength, hardness and grain size. On this basis, nickel appears to be slightly more effective as an activator than palladium, in contrast to the earlier work, but this is based on results obtained at higher sintering temperatures than those of the earlier studies.


Fig. 3 of tungsten particles which have been coated with a metallic activator.

These two models show different representations of the sintering

(a) The model of Brophy, Hayden and W N (3) has tungsten diffusing through the carrier (activator) phase, away from the line joining the centres of adjacent particles, to be redeposited elsewhere on the particles as indicated by the arrows. (b) The model of Toth and Lockington (9), where dissolution of tungsten at the activator-tungsten interface is followed by volume diffusion outwards through the activator layer and subsequent surface diffusion, this being the rate controlling step. Diffusion through the activator layer to the contact point between adjacent particles results in the formation of sintering “necks”

TUNGSTEN

These results show that the stronger activators also enhance the associated grain growth in the final stage of sintering. The higher densities (lower porosity) achieved are also reflected in higher values of compressive strength and hardness.

Samsonov and Jakowlev summarised their findings in terms of the position of the activating element in the Periodic Table,

Figure 4. The arrows indicate an increasing degree of activation. They interpreted these results in terms of the electron structure of the activators and tungsten; an increase of the stable d-bonds in the system lowers the free energy, activating the sintering process in which diffusion is accelerated by the activators for which tungsten acts as an electron donor.

More recently, German and his co-workers

Tabla 111

Dependence of the Properties of Tungsten on the Activating Element at the Optimum Concentration and Sintering Temperature (10)

Activator, weight

per cent

w Fe (0.5- 1 .O)

Ni (0.2-0.4)

Ru (1.0) Rh (0.5)

CO (0.3-0.4)

Pd (0.3-0.4)

0 s (1.0) Ir (1.0) Pt (1.0)


OC

2000

1600 1600

1 400- 1600

1600- 1800 1600

1400- 1600

2000 2000

1800-2000

Density, g/cm3

16.1

17.4- 17.95 17.4- 17.95 18.1 - 18.4

17.4 17.8

18.1 -18.35

16.1 16.7

17.6- 17.9

Compressive strength, kg/mm*

80

92-96 83-87 91 -95

77 71

83-90

80 98

88-93

Hardness, kg/mm2

181

310-390 277-282 280-306

309 290

290-300

181 238

305-330

Tungsten grain

size, pm

5-7

12-15 20-25

100- 1 20

15-20 10-1 5 20-25

5-7 5.5-7 20-30


have investigated the activated sintering of tungsten in more detail (I I - 13). German and Ham (I I) confirmed that palladium is the best metallic activator for the sintering of tungsten in the range 1100 to 140o0C, as shown in Figure 5 . This shows that, for both palladium and nickel, enhancement of sintering starts at approximately I monolayer thickness of additive and peaks at a thickness of 4 monolayers. Sintering in a moist hydrogen atmosphere was found to be detrimental to palladium activation

TI y

Fig. 4 Trends in the activated sintering of tungsten are related to the position of the activating element in the Periodic Table, as proposed by Samsonov and Jakowlev (10). l%e arrows indicate increasing degrees of sctivation

PALLAOIUM,wetght per cent 0.01 0.1

NICKEL.Welght per cent 0.01 0.1

1

EOUIVALENT MONOLAYER THICKNESS

Fig. 5 The effect of the thicknees of the palladium or Rickel activators upon the linear shrinkage of tungsten powder sintered at 1200 and 130OOC in dry hydrogen is shown, d e r German and Ham (11)

Tungsten+palladium, 130OOC A Tungsten + nickel, 1300 OC v Tungsten+palladium, 120OOC 0 Tungsten+nickel, 1200OC

. for one tungsten powder, but beneficial for a second. The apparent activation energy is lowered on sintering in a moist atmosphere.

German and Munir (12) extended this work to other Group VIII elements including platinum, and confirmed that enhanced sintering commenced at about I monolayer thickness and peaked at 4 monolayers. They found the effectiveness of the activator to be in the order:

P d > N i > P t = Co>Fe>Cu Below 130o0C, iron was more effective than platinum and cobalt. In the case of palladium and nickel, where sintering progressed to the second stage, extensive tungsten grain growth was observed. The onset of grain growth was associated with a decline in the shrinkage rate. The authors found a time dependence of the shrinkage for all activators, similar to that found by Toth and Lockington, favouring


volume diffusion of tungsten through the activator layer as the rate controlling mechanism. The addition of 0.4 weight per cent palladium was found to increase the apparent grain boundary diffusion rate by about 6 orders of magnitude, corresponding to a decreased activation energy. The measured activation energies decreased in the order of increasing activator effectiveness, palladium having the lowest value. This was related to the electron structure modifications as postulated by Samsonov and Jakowlev (IO), that is the transition metals with unfilled d-shells are the optimal activators for tungsten. Based on this concept, the authors suggest that palladium and nickel are optimum activators for all refractory metal powders.

Later work by Li and German examined the properties of palladium- and nickel-activated tungsten sintered with optimum activator content in the temperature range 1200 to 16ooOC (13). Hardness levels were in the order Pd > Ni > Co > Fe at lower temperatures, as can be seen in Figure 6, but were closer together at the higher temperatures. In the case of transverse rupture strength, nickel-activated tungsten was stronger than palladium-activated tungsten, the strength decreasing with increasing sintering temperature above 140ooC due to rapid grain coarsening. For the 0.43 weight per cent palladium-activated material, the grain size increased from 4.5pm at 1200~C to 18.opm at 140oOC and to 28.5pm at 1600OC.

Recent work on activated secondary recrystallisation of heavily-drawn doped tungsten wire has provided additional evidence for the influence of the activators during sintering (14). In this work the tungsten wire was coated with palladium, platinum or nickel prior to annealing and the rate of secondary recrystallisation measured. The highest rate of recrystallisation was found in the presence of palladium, followed by nickel and then platinum, grain growth being induced at temperatures several hundred degrees lower than uncoated tungsten wire. The process was controlled by the pene- tration of the activating elements into the wire. The diffusivities of these were found to be

much higher than in prerecrystallised tungsten, which is attributed to the high diffusivity paths through an intergranular phase formed by the activator which segregates to the grain boundaries. Auger electron spectroscopy revealed this layer to be about 2nm thick for both palladium and nickel. The measured diffusivities of the activators were in the order:

Pd > Ni > Pt > CO Studies by Gessinger and Buxbaum on elec-

tron emission from thoriated tungsten cathodes has shown that platinum can also activate enhanced diffusion of thorium to the surface along grain boundaries, enabling the temperature limit for electron emission to be extended

80, 1 Pal lad i urn

Untreated

I I

I +

K 4 0 0 - c v)

W

3

2

300- U W

U

9 200-

E z

W 0 100.

U W

P 1200 1400 1600

SlNTERlNG lEMPERATURE,'C

Fig. 6 The hardness and the strength of tungsten after activated sintering with various activators is shown here as a function of sintering temperature, from Li and German (1 3)


from 1950 to 215oK and the maximum emission current to be increased from 3 to 7.5 A/cm2 (IS). This work demonstrates that platinum group metals not only enhance the diffusion of tungsten, but can also enhance the diffusion of other elements in the tungsten grain boundaries.

Molybdenum and Other Refractory Metals

As with tungsten, several investigators have shown that both palladium and nickel can enhance the sintering of molybdenum, for example see References 16 to 18. Further, more detailed work on the activated sintering of molybdenum by platinum group metal additions has been carried out by German and his co-workers in the U.S.A. (19, 20). Their work on the heterodiffusion modelling of tungsten was extended to molybdenum where the effect of I 3 transition metal additions including rhodium, palladium, iridium and platinum was examined in the temperature range 1000 to 135oOC (19). Again, they found that activation of sintering commenced at activator concentrations equivalent to I monolayer thickness and reached the maximum effect at about 10

monolayers’ thickness, although this plateau shifted to greater thicknesses with increasing sintering temperature. They confirmed that palladium was the best activator for molybdenum, with the degree of effectiveness being in the order:

Pd > Ni > Rh > Co > Pt > Au > Fe As in the case of tungsten, iridium was

detrimental to the sintering of molybdenum. The activation energy for sintering decreased with increasing effectiveness of the activator, that for palladium-activation being 280 k J/mol (66.9 kcal/mol) compared to 405 kJ/mol (96.8 kcal/mol) for untreated molybdenum. This decrease in activation energy for palladium, nickel and platinum was observed to be concentration dependent, a rapid decrease occurring at about I monolayer thickness and reaching a minimum value at the optimum concentration of about 10 monolayers. The authors concluded that the sintering process was in accord with the

grain boundary heterodiffusion model developed earlier for tungsten (21).

Later studies by German and Labombard (20) on palladium, nickel and platinum additions to two different molybdenum powders of the same particle size sintered at low temperatures (1050 to I I 50°C) confirmed the earlier findings, namely that palladium is the best activator, followed by nickel and platinum, and that sintering behaviour conformed to the heterodiffusion model.

German and Munir also studied the activated sintering of hafnium (22) and tantalum (23) with transition metals as part of their broader investigation into the mechanisms, particularly the d-electron exchange model proposed by Samsonov (10). In the case of hafnium, the activators were added to a thickness equivalent of 4 monolayers. Isothermal sintering experiments in the range 1050 to 145oOC showed densification after I hour in the following order of enhancement:

Ni > Pd > Co > F’t Cobalt and platinum were only beneficial at temperatures above about 130oOC. Unusually, a non-Arrhenius temperature dependence was found for the activated sintering, and this was confirmed by constant heating rate experiments which showed sharp peaks for some activators at varying temperatures. These peaks occurred at about 1375OC for palladium and about 1240OC for nickel, for example, and are indica- tive of an optimum sintering temperature for maximum densification enhancement. It was concluded that the activated sintering of hafnium does correlate with the electron structure model, although the activators only impart a limited benefit.

In their study of the activated sintering of tantalum in the range 1250 to 170ooC, German and Munir found only slight enhancement with platinum, palladium and rhodium (23). The poor enhancement of palladium was particularly surprising, but examination of fractured surfaces suggested that palladium enhanced only surface diffusion, not bulk diffusion.

The use of palladium and nickel as activators in the sintering of chromium has been studied


Fig. 7 This geometric model of the heterodiffueion controlled activated sintering process shows the activator layer wetting the interparticle grain boundary, after German and Munir (29)

at the Tokohu University in Japan (24). It was found that palladium enhanced sintering considerably, the degree of enhancement reaching a plateau at about 0.8 wt. per cent palladium over the range 1050 to 120oOC. Above 120ooC, on sintering for I hour, the extent of enhancement became suppressed; this was mainly an effect of the higher density levels achieved at the higher temperatures and a reflection of the retardation due to grain growth in the second stage. In contrast, nickel had little activating effect. The relative behaviour of palladium and nickel was interpreted by the authors in terms of the mutual solubility criterion suggested earlier by Hayden and Brophy (7). Palladium- chromium fulfils this requirement whereas nickel-chromium does not.

The activated sintering of rhenium and tungsten-rhenium mixtures has been studied by several investigators (25-28). Dushina and Nevskaya found that on sintering rhenium for 2 hours in the range 1300 to 20oooC, substantial enhancement of sintering occurred with palladium contents of 0. I to 0 .5 weight per cent (25). Maximum enhancement was found in the range 0.2 to 0.4 wt. per cent palladium. This enhancement was observed to be accompanied

by substantial grain growth, grain sizes of 10 to I 5pm being observed compared to I to 2pm for untreated rhenium. Sintering at 180o0C produced densities of 92 per cent in 0.2 wt. per cent palladium-activated rhenium and only 81 per cent for untreated rhenium.

In their study on the sintering of rhenium, German and Munir found that at 10ooOC only platinum enhanced sintering, while elements such as palladium, nickel, iron and cobalt inhibited densification (26). The enhancement effect of platinum commenced at a thickness of about I monolayer, reaching a peak at about 2

monolayers. At 140ooC, both platinum and palladium enhanced sintering, platinum becoming effective at about I monolayer, rising to a plateau of maximum effectiveness at about 4 monolayers. Palladium acts less rapidly, reaching that of platinum at about 10 monolayers thickness, which suggests that palladium would be better than platinum at higher concentrations. The results of this study were considered to correlate with the electron structure model reasonably well.

The study of palladium additions to co- reduced tungsten-rhenium powders by Shnaiderman and Skorokhod again illustrates the beneficial effect of palladium in activated sintering of refractory metals, although in this instance palladium-rich alloy interlayers are formed at the grain boundaries (28) .

Models of Activated Sintering As we have seen, the activation of sintering

refractory metal powders by transition metal elements has been interpreted in terms of several models, which are generally qualitative in nature. The results of the many studies on several refractory metals have shown a reasonably consistent pattern in that the most beneficial activators are palladium, nickel and platinum, generally in that order. Since these three elements sit in the same column of the Periodic Table, it is reasonable to assume that their role is related to their electronic structure and its ability to promote rapid diffusion of the refractory element. The time, temperature and activator concentration dependencies are also


MODEL ----- EXPERIMENTAL CONSENSUS - Fig. 8 The position of the activator in the Periodic Table affects the densification of the tungsten. There is good agreement between the predictions of the heterodiffusion model (29) and experimental consensus

similar for all the refractory metals studied, which suggests that there is a common basis for a generalised model (29).

The initial model postulated by Hayden and Brophy was based on a solution-precipitation approach in which the relative solubilities of the activator in the refractory element and the refractory metal in the activating element should be low and high, respectively (7). In this model, illustrated schematically in Figure 3(a), the refractory element diffuses away from the interparticle boundary and is redeposited elsewhere on the particle surface-as indicated by the arrows in the Figure. Experimentally the rate controlling step is found to be either refractory metal diffusion at the interface with the activator layer, or refractory metal solution in the activator layer.

Later, Samsonov and Jakowlev proposed that activated sintering was a consequence of the electronic structure stabilisation of the refractory metal caused by the additive metal (10).

They based this approach on the argument that a metallic system containing partially filled d-subshells becomes more stable as the number of d5 and d * O electron configurations increase. The refractory element acts as an electron donor, and this ease of electron transfer gives

rise to the high solubility in the activating element.

A more recent proposal by German and Munir takes this model further (21) and applies the Engel-Brewer theory (30) to the prediction of the activation energies for the diffusion of refractory metals through the activator layer. In this quantitative model the activator has a role in providing enhanced grain boundary diffusion of the refractory metal. This is shown schematically in Figure 7, with the activator layer wetting the interparticle grain boundary. This is taken from Reference 29, where a more detailed description of these models is given. The relative solubility criterion is a prerequisite for enhanced diffusion of the refractory metal. Enhanced mass transport, and hence densification, results from the lowering of the activation energy for the refractory metal in the activator.

German and Munir have shown (29) that their calculated values of activation energy for diffusion of molybdenum agree well with experimentally determined values (19). These calculations indicate that palladium, nickel and platinum are the best activators, as shown experimentally for several refractory metals. The predicted shrinkages for molybdenum also


agree well with experiment, as shown in Table IV (29). Figure 8 shows the good agreement between their predictions and the experimental consensus for tungsten in terms of the position of the activator in the Periodic Table. This clearly demonstrates the superiority of palladium as an activator, with rhodium and platinum also in significant positions.

More recently, Miodownik has proposed a quantitative figure of merit for assessing the potential of additive elements as activators (31). This parameter, 4, has been derived by com- bining the relevant heats of solution, surface energies and the energy of vacancy formation in the activator, and is based on the underlying thermodynamic parameters that are responsible for the phase equilibria; the solubility criterion of the earlier models is an aspect of the latter:

where AH,, AH, and AH, are thermodynamic functions related to solubility, segregation and diffusion, respectively. Using calculated values of for the sintering of tungsten, Miodownik’s predictions are correct for 12 out of 14 activator elements shown in Figure 8, the only dis- crepancies being manganese and gold. Once again palladium is predicted to be the most effective activator.

4 = AH, + AH2 + AH3

Properties of Sintered Materials While there has been a considerable number

of studies into the phenomenon of activated sintering, relatively few studies have measured the properties of the sintered materials. Fracture is generally intergranular in nature, suggesting that the activator-rich grain boundaries are paths of easy fracture. Strength and hardness are very density dependent and the effectiveness of the activator on densification clearly plays a major role. Thus, both type and concentration of the activator influence sintered strength, as shown in Table I11 and Figure 6. Strengths as high as 1050 MPa have been shown for palladium-activated tungsten (10).

No data have been presented for high temperature creep properties, but the enhancement of grain boundary diffusion in the

Table IV

Comparison of Predicted and Measured Shrinkage for the

Activated Sintering of Molybdenum Powder (29)

2.2pm size: sintered 1 hour at 125OOC in hydrogen

I Shrinkage, per cent Activator 1 Predicted I Measured

Untreated Mo Pd Ni Pt co Fe Cr

1.6 8.9 6.9 4.7 4.6 3.5

~ 1 . 1

2.1 8.2 7.2 3.6 4.3 2.2 1 . 1

presence of activators would be expected to promote diffusional creep of the Coble type.

As stated above, the use of platinum group activators can promote enhanced electrical properties: Gessinger and Buxbaum have utilised the increased grain boundary diffusivity in platinum-activated thoriated-tungsten emitters to improve electron emission ( I 5 ) .

Summary This paper has reviewed the numerous

studies of the activated sintering of refractory metals by transition metal additions and has shown that the platinum group metals, and particularly palladium and platinum, even at amounts of less than I per cent by weight, are very effective in promoting densification at temperatures several hundred degrees lower than would otherwise be required. The models developed to describe the phenomenon have been examined and those of German and Munir (29) and Miodownik (31) have been shown to predict the order of effectiveness remarkably well. Significantly, palladium is predicted to be the best activator element for several refractory metals including tungsten and molybdenum, in accord with experimental findings. The enhanced densification that results from the use of platinum group metal activators leads to improved strength properties.


I

2

3

4

5

6

7

8

9

I 0

I1

I2

13

I4

I5

16

References

J. Kurtz, Proc. Second Annu. Spring Meeting, I7 0. Neshich, V. V. Panichkina and V. V. Metal Powder Assoc., 1946, 40 Skorokhod, International Team for Studying J. Vacek, Planseeber. Pulvermetall., 1959, 7, 6

“powder all^^^>,, ed. W. hszbski , NME- MPI, Interscience, New York, 1961, p. 113 J. H. Brophy, H. w. Hayden and J. wulff, Trans. AIME, 1962, 224, 797 H. W. Hayden, S.B. Thesis, Massachussetts Institute of Technology, Metallurgy h p t . , 1960 J. H. Brophy, H. W. Hayden and J. wulff, Trans. AIME, 1961, 221, 1225 H. W. Hayden and J. H. Brophy, 3. Electrochem.

H. W. Hayden and J. H. Brophy, J. Less- Common Met., 1964, 6, 214 I. J. Toth and N. A. Lockington,J. Less-Common

G. W. Samsonov and W. I. Jakowlev, Z . Metallkd., 1971, 62, (S), 621 R. M. German and V. Ham, Int. J . P m d e r Metall. Powder Technol., 1976, 12, (2), 115 R. M. German and Z. A. Munir, Metall. Trans.

C. Li and R. M. German, Metall. Trans. A , 1983, 14, 2031 L. R’ Warren and E’ Henig3 to be Powder Metall. Ceram., 1980, 19, (I), 27 presented at the 7th Int. Risd Symposium, Roskilde, Denmark, Sept. 1986 G. H. Gessinger and Ch. Buxbaum, “Sintering and Catalysis”, ed. G. C. Kucqnski, Plenum, New York, 1975, p. 295 V. V. Panichkina, V. V. Skorokhod and A. F. Khrienko, Soviet Powder Metall. Ceram., 1967,6,

Sintering, ITS 27, 1972

shev, L. L. Kolomiets and L. I. Schnaiderman, Soviet Powder Metall. Ceram., 1976, 15, 435

19 R. M. German and Z. A. Munu, J. Less-Common Met., 1978, 58, 61

2o R- M. German and c. A. In[. 9. PowderMetaN. Powder Technol-, 1982, 1% (2), 147

21 R. M. G e m , “Sintering-New Developments”, 4th Int. Conf. on Sintering, ed. M. M. Rustic, Dubrovnik, Sept. 1977, Elsevier, 1979, p. 257

22 R. M. German and 2. A. Munir, 3. Less-Common Met.’ 1976’ 46’ 333

23 R. M. German and Z . A. Munir, Powder Metall., 1977y 20’ (3)’ 145

24 R. Watanabe, K. Toguchi &d Y. Masuda, Sci. 1983’ Is’ (’)’ 73

25 0. V. Dushina and L. V. Nevskaya, Soviet Powder Metall. Ceram., 1969, 8 , 642

26 R. M. German and Z. A. Munir, J. Less-Common Met‘’ 1977’ 53y 14’

27 V. V. Panichkina, L. I. Shnaiderman and V. V. Skorokhod, Dokl. Akad. Nauk. Ukr. SSR,’ 1975,

28 L. I. Shnaiderman and V. V. Skorokhod, Soviet

29 R. M. German and 2. A. Munir, Rev. Powder

30 L. Brewer, “High Strength Materials”, ed. V. F.

31 A. p. Miodownik, “Shtering: Theory and Prac- Metall.,

J. H. Brophy, L. A. Shepherd and J. Wulff, I 8 v. v. Skorokhod, s. M. solonin, L. 1. Cherny-

Sot., 1963, 11% (7), 805

Met., 1967, 12, 353

A , 1976, 7A, 1873

A, (9, 469

Metall. Phys. Ceram., 1982, 2, (I), 9

Zackay, J. Wiley, New York, 1965, p. 12

tice”, H a m w e , October 1984; 558 1985, 28, (31, 152

Oxidation Behaviour of Some Platinum Alloys For a limited number of specialised applica-

tions, such as for jewellery, the aesthetic appearance of a material is a crucial factor. Clearly the appearance must be pleasing at the time of purchase, and for precious metal items it is equally important that they should not lose their appeal with use or the passage of time.

Recently the results of a study sponsored by Rustenburg Platinum Mines Limited into the oxidation behaviour of a number of commercially available platinum-rich and 18 carat gold alloys has been reported (A. Wells and I. Le R. Strydom, J. Muter. Sci., Lett., 1986, 5 , (7), 743-746). The reactivity of the alloys was assessed by examining them in both the as- received condition and after heating at I~oOC for 24 hours under a flow of oxygen.

After this treatment it was observed that both the gold alloys had undergone a colour

change, but no changes were perceived on the four platinum alloys, which contained 5 weight per cent cobalt, 10 and 15 palladium, and 7 palladium plus 3 cobalt.

Auger electron spectroscopy detected surface segregation of alloying elements on all samples, except for the alloy containing cobalt, an element for which the technique is insensitive. In general, the platinum alloys showed no significant changes as a result of the oxidation treatment, although minimal oxidation-enhanced copper enrichment was observed on the surface of the platinum-15 palladium alloy, in which a small amount of copper is incorporated.

From this study it was concluded that the platinum alloys examined were significantly less environmentally reactive than the two gold alloys, under oxidising conditions at near ambient temperatures.


Tenth International Precious Metals Conference SELECTED PLATINUM METALS PAPERS REVIEWED

By Roger J. Runck International Precious Metals Institute, Allentown, Pennsylvania

On 8th to 12th June 1986, the International Precious Metals Institute celebrated its tenth anniversary with its annual conference. This was held at the Hyatt Lake Tahoe Hotel in Incline Village, Nevada, the purpose being to bring together worldwide specialists in all phases of the precious metals industry for an exchange of information.

The meeting was attended by 456 people who came from 26 of the 50 states in the United States of America and from 17 other countries. The technical sessions included 68 papers in 12 sessions covering such subjects as recovery of precious metals from primary as well as from secondary sources, evaluation of analytical procedures, environmental considerations, economics and various applications.

Fuel Cell Technology The application of platinum group metals in

fuel cells was reviewed with a discussion of some technical developments and estimates of the requirements for platinum in the next two decades. Maynard K. Wright of the Westing- house Electric Corporation in Pittsburgh, Pennsylvania, reported that the company’s ob- jective is to commercialise phosphoric acid fuel cell technology in the 1990s. If successful, the estimated cumulative platinum requirements for their programme would reach some 850,000

troy ounces by the year 2005. And the year 2005 has some significance

because estimates of phosphoric acid fuel cell development, presented by A. J. Appleby of the Electric Power Research Institute in Palo Alto, California, project that this production will peak in the years 2005 to 2009, by which time more efficient fuel cell systems using non-

Platinum Metals Rev., 1986, 30, (4), 196-197

noble metal catalysts may of the market.

Philip N. Ross of the

have captured much

Lawrence Berkeley Laboratory in Berkeley, California, pointed out that commercial use of fuel cells was dependent on more efficient use of platinum than was possible with the platinum-black deposit as prepared by the Adams method. With improved technology, such as deposition of platinum by adsorption from colloids rather than by electrodeposition, a remarkably uniform distribution of platinum crystallites can be obtained. With this, and with engineering improvements in electrode technology and stack engineering at United Technologies, platinum loadings have been reduced by two orders of magnitude with no sacrifice in performance.

Satoshi Motoo of Yamanashi University in Japan discussed the theoretical performance of gas diffusion electrodes for fuel cells and electrolytic cells. This ties in with a programme by Prototech Company in Newton, Massa- chusetts, to replace the conventional lead anode used in electrowinning zinc with a hydrogen diffusion anode (HDA). Amiram Bar Ilan of Prototech described a development programme in West Germany to demonstrate the benefits of this substitution which is reported to save more than one-half the DC energy at the expense of hydrogen, eliminate acid mist, and alleviate cooling requirements. They propose to retrofit existing plants as well as to use HDAs in new plants where even greater benefits could be realised. Since the HDAs generate hydrogen, this could be used in hydrogen-air fuel cells to generate all the electricity needed for the zinc tankhouse. The platinum requirement to

196

retrofit substantially all existing zinc tank- houses with HDAs is estimated to be of the order of 130,000 troy ounces.

Z. George Swiatek of Diesel Controls Ltd., Ontario, Canada, described the construction and performance of a metallic substrate as a honeycomb platinum catalyst support for a catalytic converter to purify diesel engine exhausts. Called a Mine-X design, the converter is superior to units using a ceramic honeycomb due largely to its higher thermal conductivity which provides better distribution of heat. Advantageously, the units can be brazed to the container.

Coatings for Refractories Interest continues in using platinum group

metals as protective coatings particularly against high temperature oxidation of refractory substrates. Richard P. Walters of the U.S. Bureau of Mines described work on the electrodeposition of platinum group metals in molten cyanide. An equimolecular mixture of sodium and potassium cyanide was used. Thick platinum coatings produced were adherent and fully ductile, but not pore free. The researchers suggest laser processing to reduce porosity.

John T. Harding of Ultramet in Pacoima, California, coated refractory metals with iridium, platinum and rhodium from acetyl- acetonate compounds by chemical vapour deposition. Of these, iridium was preferred and claims of effective protection in air at 2000OC over 5 hours were made. Work is continuing with alloys of these three metals.

Petroleum Refining While not all of the steps in the refining of

fossil fuels (gas, coal and petroleum) into fuels or chemicals use noble metal catalysts, these are essential in many of the steps. The subject is too complex for a useful short summary. For example, in petroleum refining there are 25 to 35 different commercial platinum catalysts available. All consist of platinum on alumina.

Those used in ' petroleum refining were described by Arthur H. Neal, Exxon Research and Development Laboratories in Baton

Rouge, Louisiana, while precious metals used in the production of petrochemicals were described by R. J. Farrauto of Engelhard Cor- poration in Edison, New Jersey.

In petroleum refining, platinum catalysts are particularly necessary for the paraffin isomerisation and catalytic reforming processes which are important in the production of high octane motor gasoline. Iridium and palladium also are used as catalysts. Recovery of these catalysts is high, however, and demand for platinum group metals in this industry is modest compared with other industries.

For petrochemicals, the precious metals used as catalysts are primarily composed of platinum, palladium, rhodium, or silver, and sometimes a combination of these or other metals. Catalysts may consist of platinum metals plated on carbon particles or alumina honeycomb, or as wire mesh screens. Homo- geneous catalysts of noble metals (those dis- solved in the reactant phase) are also used, but only in a very few processes.

Related to petrochemicals was a paper by T. A. Koch of E.I. du Pont de Nemours in Wilmington, Delaware. Dr. Koch described research to understand and improve the behaviour of rhodium-platinum catalysts used in the manufacture of hydrogen cyanide from methane and ammonia. While consistency in performance of these catalysts was improved somewhat by tighter limitations on impurities, especially iron, no solution to the problem of rapid deterioration in catalyst performance was found. Research, however, disclosed that there is rapid restructuring of the platinum alloy which produces dislocations and voids which result in expansion in the volume of the wires in the mesh.

Of the 68 papers presented, 48 (in whole or in part) were bound in book form prior to the conference. The book is available from the International Precious Metals Institute, Government Building, ABE Airport, Allen- town, Pennsylvania 18103. The price is $25 for IPMI members, $35 for others, plus $2.50 for postage and handling a single copy and $0.75

for each additional copy.


Alexander Abramovich Grinberg RESEARCH ON THE CO-ORDINATION COMPOUNDS OF THE PLATINUM METALS

By Professor Y. N. Kukushkin The Lensoviet Institute of Technology, Leningrad

This year marks the twentieth anniversary of the death of Academician A. A. Grinberg who, fifty years ago, founded a new field of science to study the chemistry of co-ordination compounds of the platinum metals at the Lensoviet lnstitute of Technology in Leningrad. His academic lije was devoted to this subject and his many contributions continue to form a source of inspiration to his successors.

Alexander Abramovich Grinberg ( I - 5 ) , a full member of the U.S.S.R. Academy of Sciences, was born in St. Petersburg on 2nd May 1898. After graduating from the Gymnasium with a gold medal in 1916, he entered the Physico- Mathematical Faculty of the Petrograd State University to join the medical group. Later he moved to the chemistry department of the same faculty. In those times, the university pro- fessors included such distinguished chemists as

A. E. Favorsky, L. A. Chugaev, V. N. Ipatiev, M. S. Vrevsky, V. E. Tishchenko, Yu. S. Zal- kind, and S. V. Lebedev. This fact of his transfer from the medical group to the department of chemistry was later used by his friends to make jokes to the effect that “the chemists had stolen Alexander Abramovich from medicine”.

Grinberg finished at the university in 1924, while in 1920 he began his work at an institute founded by L. A. Chugaev to study platinum and the other noble metals. Late in the nineteenth and early in the twentieth century Russia was the main supplier of platinum to the world market from the rich platinum deposits discovered in the Urals in 1822. Thus, platinum and its satellites were one of the riches of Russia, and it was of course necessary to study these riches. Immediately after the Great

Alexander Abramovich Grinberg 1898-1966

A full Member of the U.S.S.R. Academy of Sciences and Head of the Chair of General and Inorganic Chemistry at the Lensoviet Institute of Technology in Leningrad, Grinberg developed the theory of co-ordination chemistry on the basis of platinum metal compounds. His enthusiasm was to influence many of his former students to devote their academic careers to the study of co-ordination chemistry in general and the chemistry of the platinum metals in particular, as he had done


October Revolution of 1917, in those difficult times for the newly born nation, the young government of Soviet Russia made a decision to establish a network of scientific research institutes and among the first research establish- ments founded in April 1918 was the Institute for Platinum Studies.

A. A. Grinberg began working in this institute almost from its start-up and he continued there until 1934 when the institute was transferred to Moscow to become the main core of the Institute of General and Inorganic Chemistry of the U.S.S.R. Academy of Sciences.

The chemistry of platinum metal compounds is essentially that of their co-ordination compounds, and the theory that correctly described the main features of their structure was presented by Alfred Werner as far back as 1893. This theory was by no means accepted immediately by all chemists, and critical comments continued until the 1930s. L. A. Chugaev was quick, however, to recognise the advantages of Werner’s theory, and he adopted it as a guiding principle in the research activities on the Group VIII elements of the Periodic System and above all platinum metals, and he is rightly considered to be the father of Soviet co-ordination chemistry. Outstanding contributions to the chemistry of co-ordination compounds were made by the pupils of L. A. Chugaev and by his associates in the Institute of Platinum, such as I. I. Chernyaev, V. G. Khlopin, N. K. Pshenitsyn, V. V. Lebedinsky, E. Kh. Fritsman, and many others. Among these, an important part was played by A. A. Grinberg.

Grinberg started his pedagogical activities in 1928 when he became an assistant professor and then privardocent, while from 1932 he became Professor of General and Inorganic Chemistry at the I. P. Pavlov Institute of Medicine in Len- ingrad. From 1936 he held the Chair of General and Inorganic Chemistry at the Lensoviet In- stitute of Technology. There Grinberg created a large scientific school of his own which produced many of the leading Soviet specialists in co-ordination chemistry and in the chemistry of platinum metals. His broad interests in science,

combined with his enthusiasm and friendliness, drew associates and students closer to him, and under the influence of his bright personality many of the graduates from the Lensoviet In- stitute of Technology devoted their life to co- ordination chemistry and to the chemistry of the platinum metals. It was here that he wrote the textbook “Introduction to the Chemistry of Complex Compounds”, which was published four times and translated into many languages. For several decades this was a standard text for large numbers of students, post-graduates, institute teachers and research associates. Addi- tionally, in 1936, he edited the Russian translation of A. Werner’s “New Ideas in the Field of Inorganic Chemistry”, published in the Soviet Union. (One of the two translators of this book was A. A. Grinberg’s mother, Yekaterina Mikhailovna.)

During World War I1 Grinberg was evacuated with the Institute of Technology from Leningrad to the town of Kazan. There he worked shoulder to shoulder with A. E. Arbuzov, an outstanding researcher of organic phosphorus compounds, and the joint activities of these two men of science in Kazan resulted in the establishment of a laboratory to study the complex compounds of platinum metals with organic phosphorus ligands. This laboratory still remains very active.

In Kazan, Grinberg became Head of the Laboratory at the Institute of Radium which had also been evacuated from Leningrad. Co- operation with this institute, however, had begun in Leningrad several years before just after the first European cyclotron was com- missioned there in 1936. Already in the pre-war years, Grinberg, together with F. M. Filinov, used the cyclotron to obtain radioactive isotopes of platinum, iridium and bromine which were utilised in the study of co- ordination compounds. Grinberg headed this laboratory in the Institute of Radium until his death.

In 1943 Grinberg was elected Corresponding Member, and in 1958 Full Member, of the U.S.S.R. Academy of Sciences, while for his contribution to science and for his scientific


organisation activities, he was awarded many high government honours, including one Order of Lenin, one Order of the Red Banner of Labour and an Order of the Red Star. He was also given the title of Worker Emeritus of Science and Technology.

Grinberg’s Publications The first papers written by A. A. Grinberg on

research in the co-ordination compounds of platinum concerned stereochemistry. At this time opponents of Werner’s co-ordination theory were doing their utmost to invalidate the square-planar structure of platinum(I1) com- lexes. Such publications were written, in particular, by Reilen and Nestle (6) in the late 1920s and also by Drew and co-workers in the early 1930s (7). On the basis of the measurement of molecular weights of Peyrone’s chloride (cis-[Pt(NH,),Cl,]) and of Reise’s second base chloride (trans-[Pt(NH,),Cl,I) in liquid ammonia, Reilen and Nestle arrived at the conclusion that the latter complex was essentially a dimer and, consequently, the two complexes were not isomers. However, Grin- berg synthesised isomeric [Pt(NH,),(SCN),l complexes and measured their molecular weights in acetone (8). These happened to be equal, which confirmed that the complexes were isomeric. If complexes of this composition were isomeric they must have a square-planar structure, which supported Werner’s theory.

Also of importance was Grinberg’s research using ligands which form chelate rings, such as C,o:-, NH,CH,COO-, to determine the geometric configuration of [Pt(NH,),Cl,l complexes (9). For example, when interacted with oxalic acid and glycine, the cis-tPt(NH,),Cl,I complex forms [Pt(NH,),(C,04)l and [Pt(NH,),(NH,CH,COO)l+ , respectively, while trans-[Pt(NH,),Cl,] leads to the formation of trans-[Pt(NH,),(C,O,H),l and trans-[Pt(NH,),(NH,CH,COOH),12+. In other words, one mole of the ligand reacts with one mole of the complex in the first case, and two moles react in the second, which was consistent with the proposed isomeric structures.

In addition the successful synthesis of the

cis-trans-isomeric glycine compounds [Pt Gl,], where (Gl=NH,CH,COO-), (10) can be related to the research in stereochemistry and testified to the square-planar structure of the given complexes. Attempts had been made before Grinberg’s time to synthesise these isomeric complexes predicted by the co- ordination theory, but without success.

In the late 1920s and early I ~ ~ O S , many researchers were also attempting to synthesise the analogous isomeric complexes of palladium(I1). One of the goals of such syntheses was to determine whether these complexes had a square-planar or a tetrahedral structure. Back in 1927, Krauss and Brodkord (11) reported that they had obtained isomeric complexes of the [PdA,X,l type (where A=ammonia or organic amines). Grinberg (12) and Drew, Pinkard, Preston and Wardlaw (I 3) reproduced their data and arrived at the conclusion that they had obtained [PdA,X,l and [PdA,l- [PdX,], but not isomeric compounds. Based on this, Drew and colleagues rejected the possibility that geometrical isomerism existed in the complexes of palladium(I1). At the same time, Grinberg directed his efforts to obtain the missing isomer. Properties of palladium(I1) complexes of the type [PdA,X,l had been obtained by that time and these pointed to a trans-configuration. Utilising the method of synthesising the cis-[Pt(NH,),Cl,I complex, Grinberg was fortunate and synthesised cis-[Pd(NH,),Cl,I (14), thus confirming the square-planar configuration of palladium(I1) complexes.

One of the central problems of co-ordination chemistry has been, and to some extent still remains, the problem of the mutual influence of ligands, particularly on reactivity. In 1926 I. I. Chernyaev discovered the trans-influence phenomenon (15) which was later expressed in the form of a law ( I 6). Throughout all of his activities in science, Grinberg was busy in research directed to the experimental and theoretical confirmation and development of this law. In 1932, simultaneously with B. V. Nekrasov, he explained the law of trans- influence using polarisation concepts. A later


development was a rather fruitful idea concern- ing the nature of the trans-influence, from the viewpoint of the oxidative and reductive properties of ligands ( I 7).

In the first edition of his monograph, “Intro- duction to the Chemistry of Complex Com- pounds” ( I @ , Grinberg wrote: “The law of trans-influence does not presuppose in any way that the interaction of trans-groups by way of a central metal atom is the only kind of interaction which is possible between co-ordinated groups combined in one complex nucleus. It is evident that groups in the cis-position also can (and must) cause an influence on one another.” In the mid-IgSos, Grinberg experimentally demonstrated the influence of ligands in the cis- position (19). This resulted from a study of the kinetics of reactions in which chloride ligands were substituted by ammonia in the complexes:

L L

If the cis-positioned ligands did not influence one another, then the rate of substitution reactions on the co-ordinate Cl-Pt-CI in these complexes should be very similar. However, the experimental data showed that the rate of substitution in the ion [PtNH,CI,l- is higher than that in [PtCl4Iz-. The same picture could be observed from the isotope exchange of chloride ligands. Later, Grinberg and his pupils studied analogous complexes with ligands such as pyridine, aliphatic amines, ethylene, thio- ethers and sulphoxides, instead of ammonia. In general the cis-influence of these ligands was found to be in the reversed sequence compared to their trans-influence (16). For example, ammonia has a small trans-influence value but has a relatively high cis-influence. In contrast, ethylene has a high trans-influence but a low cis-influence.

A. A. Grinberg was one of the first to have used radioactive isotopes in studies on co- ordination compounds. For example, he studied the isotope exchange of the bromide ligend in the complexes [PtBr,lz- and [PtBr61Z- and obtained important conclusions (20). He asserted that in spite of the high stability of

these complex ions, the ligands in their inner spheres were labile. Also important was the conclusion that all of the bromide ligands in each of the complexes in question happened to be of equal value. From this it followed that there was no difference whatsoever between the main and additional valencies.

Grinberg’s investigations with the use of radioactive markers resulted in other very important conclusions. Suffice to say that using an example of the isotope exchange of ligands of the type [PtX41z- (where X=Cl-, Br-, I-, CN-), a seemingly paradoxical phenomenon was found: the thermodynamic stability of complexes did not agree with their kinetic lability. It appeared that the more stable the complex the faster the ligands exchanged therein. Later, a similar situation was disclosed by Hertz on type [HgX,lz- mercury complexes (21). Grinberg, however, did not think that such behaviour for identical complexes of the same metal was widespread, and he warned other researchers against making too extensive generalisations.

Kinetic research into the substitution reactions and the isotope exchange of inner- sphere ligands made it possible for Grinberg to detect the mechanism of many of the reactions. His papers show the important role played by the solvent in these reactions. It has been found that in water solutions, many isotope exchange and alkaline hydrolysis reactions of the complex compounds of platinum(I1) proceed via an initial aquation step, while in non-co-ordinating solvents exchange can be carried out by the direct substitution of ligands. The reaction mechanisms of isotope exchange and substitution in the octahedral complexes of platinum(1V) are more diversified. A substantial role in these reactions is played by the acid-base properties of the complexes, and redox mechanisms can be involved.

A great contribution was made by Grinberg towards the science of acid-base properties of co-ordination compounds. In his early research activities he showed that the following reaction, which produces an amidotetrammine complex and was first carried out by L. A.

Platinum Metals Rev . , 1986, 30, (4) 20 1

Chugaev, involved a reversible change of spectrum in the ultraviolet region: [Pc(NH3)5CIlC13 + NaOH [Pt(NHJ4(NH2)Cl1Cl2

+ NaCl + H 2 0 He also discovered that a similar change in the spectra of amine complexes of platinum(1V) influenced by an alkali could be observed in many instances, thereby demonstrating the de- protonation of the amine ligands. In this connection Grinberg put forward a supposition, later confirmed, that all of the co-ordination compounds of metals containing RH ligands were potentially acid in nature. Subsequent research activities of Grinberg and of his numerous pupils were associated with the quantitative characteristics of the acidic properties of amino- and aquo-complexes of different metals. After many years of research work, Grinberg formulated generalisations about the relationship of acidic properties of complexes and a number of factors: namely central metal charge, complex ion charge, the geometrical structure, the tendency of the free ligand towards acidic dissociation and other factors. These guidelines make it possible to predict the properties of yet unknown compounds (22).

A. A. Grinberg paid a large amount of attention to the study of red-ox properties of the

A. A. Grinberg with one of his pupils and followers in research on the co-ordination chemistry of platinum metals, Professor Y. N. Kukushkin, the author of this paper, and the present Head of the Chair of General and Inorganic Chemistry at the Lensoviet In- stitute of Technology

co-ordination compounds of platinum metals. Early in the 1930s he wrote a paper that established the possibility of quantitative oxidation of certain platinum(I1) compounds using per- manganate (23), and for many years this reaction had a significant place in analytical practice. For Grinberg it happened to be the beginning of a new direction in his research activities, that is the study of red-ox properties of co- ordination compounds. As a result of research in this direction, the influence of the nature of ligands upon a red-ox potential was disclosed, and an idea was formulated on the nature of phenomena defining the red-ox potential.

The exact nature of the nitrile-amine compounds of platinum(I1) (24) were the subject of discussion among researchers for a long time. These were synthesised for the first time in 1915 (25) and remained an enigma until early in the 1960s. Back in 1950, in his important paper about the Pt( NCCH,),(NH,),l C1, complex, Sidgwick wrote that there should not have been any doubt that platinum in that compound has a covalence of 6. In I 95 I Grinberg expressed an idea that the amino-nitrile complexes of platinum(I1) were essentially compounds with intra-sphere amidines (27). Several years later, using infrared spectroscopy, Kharitonov was

Plarinum Metals Rev., 1986, 30, (4) 202

able to confirm this supposition (28). It is known that the degree of conversion of alkyl- nitriles into amidines is not very high under ambient conditions (29). However, formation of amidines in the internal sphere of complexes becomes much easier as a consequence of their co-ordination. The effect of co-ordination on ligand reactivity continues to be a major research topic in co-ordination chemistry, particularly as it is directly related to metallo- complex catalysis.

In recent times bioinorganic chemistry has become an independent branch detached from co-ordination chemistry, and Grinberg also stood on the threshold of this field of science. Early in the I ~ S O S , he suggested that M. A. Azizov should begin to study co-ordination compounds using biological compounds as ligands. Now, the laboratory of Professor Azizov is one of the leaders in the U.S.S.R. in the field of research and application of bio- logically active co-ordination compounds.

Grinberg devoted all his adult life to co- ordination chemistry in general and to the chemistry of platinum metals in particular. He left behind for his successors a large scientific inheritance, and the thoughts and ideas expressed in his papers and monographs still continue to be used by many researchers as a source of inspiration for further investigations.

A human death is always premature. A. A. Grinberg was caught by death during a period of great creativity. Until his last days he was busy preparing a report for the International Conference on Co-ordination Chemistry (I.C.C.C.) to be held in Geneva and devoted to the centenary of the birth of Alfred Werner, creator of the co-ordination theory.

Every year, early in May, in the Lensoviet Institute of Technology in Leningrad, a ceremonial meeting is held at which the pupils and followers of Alexander Abramovich Grin- berg read a lecture about this great scientist and remarkable man.

References I Y. S. Varshavsky and M. I. Gelfman, “Alexander 17 A. A. Grinberg, Izv. Akad. Nauk SSSR, Otd.

A. Grinberg”, Nauka Publ., Leningrad, 1974 2 “Collected Articles, Academicians A. A. 18 A. A. Grinberg, “Vvedenie v Khimiu Kom-

plexnykh Soedinenii”, Goskhimizdat, Moscow- Leningrad, 1945, p. 254

19 A. A. Grinberg and Y. N. Kukushkin, Zh. Neorg. Khim.3 1957, IY 106

20 A. A. Grinberg and F. M. Filinov, Dokl. Akad. Nauk sssRp I9399 23, 918

Khim. Nauk, 1943, (9, 350

Grinberg and I. I. Chernyaev, Outstanding Soviet Chemists”, Nauka Publishers, Moscow, I970

3 Obituary notice, Radwkhimia, 1966, 8, 612 4 Y. N. Kukushkin and Z. E. Golbraikh, Zh.

5 L. K. Simonova, Zh. Prikl. Khim., 1966,39,2393 Neorg. Khim., 1966, 12, 835

6 H. Regen and K. T. Nestle, Ann, Chem. (Liebig), 21 H* G. Hertz, z. Elektmchem., 19619 65, 20 1926, 447, 211 H. D. K. D ~ ~ ~ , F. w. pinbrd, w. wardaw and

8 A. A. Grinberg, Izv. Inst. Plafiny, 1928, 6, IZZ

22 Y. N. Kukushkin, “Khimia Koordinatsionnykh Soedinenii”, Vys’shaya shkola, Moscow, 19859 P.

23 A. A. Grinberg and B. V. Ptitsyn, Izv. Inst. E. G. Cox,J. Chem. SOC., 1932, 988 256

Platiny, 1933, 1x9 77 9 A. A. Grinberg, Inst. p1arinY9 19313 8, 93 24 y. N. Kukushkin, Koord Khim,, 25 L. Tschugaev and w. hbedinski, Compt, Re&.,

26 N. v. Sidgwick, “ne aemical ~l~~~~~~ and

,, 323 10 A. A. Grinberg and B. v. RitsYn, Izv. Inst.

11 F- Gauss and F. Brodkord, z. Platiny, 1932, 9, 5s 1915, 161, 563

Their Compounds”, Oxford Univ. Press, Lon- don, 1950, VOI. 2, p. 1583

27 A. A. Grinberg and Kh. I. Gildengershel, Izv. and w. J. Wardlaw, J. Sectora Platiny IONKh Akad. Nauk SSSR, 1951,

26, I 15 Nauk SSSR, 1933, (9, 215 28 Y. Ya Kharitonov, Ni Tsa-Tsan and A. V.

Babaeva, Dokl. Akad. Nauk SSSR, 1961, 141, 645

29 J. Zimmerman, J. W. Minnis, P. Oxley and W. F. Short, J. Chem. SOC., 1949, 2097

a&?. Chem., 1927, 165, 73

12 A. A. Grinberg, h. Inst. PlatinY, 1933, 1 b 95 I 3 H. D. K. Drew, F. W. h h d , G. H. heston

SOC.9 19329 1895 14 A. A. Grinberg and V. M. Shulman, Dokl. Akad.

15 I. I. Chernyaev, Izv. Inst. Platiny, 1926, 4, 243 16 Y. N. Kukushkin and R. I. Bobokhodzhaev,

“Zakonomernost’ transvliania I. I. Chernyaeva”, Nauka Publishers, Moscow, 1977

Plarinum Metals Rev., 1986, 30, (4) 203

ABSTRACTS of current literature on the platinum metals and their alloys

PROPERTIES Specificity of Hydrogen Adsorption on Chromium-Supported Platinum Group Metal Catalysts J. ADAMIEC, React. Kinei. Caral. Lett., 1986, 30, (I), 143-147 H , adsorption on O , O , supported Pt, Pd and Rh was studied under various pretreatment conditions. The reduction temperature strongly influences the H, uptake for all these metals. Pt/Cr,O, shows an unusually high H , adsorption stoichiometry.

Magneto-Optical Properties of Vacuum- Deposited PtMnSb Thin Films T. INUKAI, hi. MATSUOKA and K . ONO, Appl. Phys. Lett., 1986, 49, (I) , 52-53 Magneto-optical properties of PtMnSb thin films, prepared by sequential vacuum deposition and annealing have been examined. Films annealed at 5oo°C exhibit a large Faraday rotation and a large polar Kerr rotation. They transmit light well in the 400-900nm wavelength range with an absorption coefficient of 3.2x10Jcm-' at 633nm.

Electrical and Structural Properties of Thin Palladium Films

Naturforsch., A , 1986, 41a, (4), 665-670 The electrical resistivity of thin Pd films deposited on amorphous substrates was measured as a function of film thickness. Structural information was obtained from AES, TEM and X-ray diffraction studies. The steep decrease of resistivity in the ultra thin region can be correlated with the formation of coherent areas in the film. A more flattened course occurs at - 8nm film thickness when a continuous film develops.

Solubility of Helium in Melts of the Metallic Glass System Pd-Ni-P and in Related Systems 1. DIETRICHS and G. H. FRISCHAT, J . Muter. s c i . , 1986,

Glass melts of Pd~o-,oNilu-,uP,4-~6 were saturated with He gas during the melt- spinning process. Pt was substituted for Pd, Mn, Fe and Co for Ni and B for P and these could also be saturated. The He could be extracted from the glasses. The He solubilities between 750 and 125oOC varied between 2 and 45 (pl He/mol glass). This method can measure very low gas solubilities in metallic glass melts where the solubilities obtained depend on the free volume and thus on the structure of the glasses and glass melts.

R. ANTON, K. HUPL, P. RUDOLF and P. WISSMANN, z.

21, (7), 2535-2539

Synthesis, Lattice Parameters and Ther- mal Expansion Coefficients of Rhodium Arsenide Rh,As and Some Substituted Compounds

GUERIN, J . Cyst. Growth, 1986, 76, (I), 135-141 The lattice parameters of cr-Rh,As obtained by direct synthesis was measured between 295 and 956K. Its thermal expansion coefficient was practically constant within this temperature range. cr-Rh,As has numerous features in common with GaAs and seems to be favourable for coherent metal/semiconductor heteroepitaxy .

Preparation and Characterization of Con- ductive IrO, Thin Films by Reactive Sputtering

Nippon Kagaku Kaishi, 1986, (3), 249-254 Transparent conductive IrO, films were prepared by reactive sputtering of an Ir target in 0,. IrO, films of 500h thickness have 85% transmittance in visible light, 60 S/cm conductivity at room temperature and sheet resistivity of 300 Q. Optical, electrical and electrochemical properties of IrO, films prepared under various sputtering conditions are described and bonding structures and valence bond profiles studied.

On l l f Noise in Ru0,-Based Thick Film Resistive Films A. KUSY and A. SZPYTMA, Solid-state Electron., 1986,

Results of I/f noise power spectral density measurements on RuO, -based thick resistive films are presented. A model of I/f noise is proposed based on the results. Films made of RuO of average particle size slightly smaller than ~ook have I/f noise relative power spectral density 4-6 orders of magnitude smaller than RuO, films of average particle size 3000A.

M. SECOUE, P . AUVRAY, Y. TOUDIC, Y. BALLINI and R.

S.-I. KAWATE, R. FUJIWARA, S. ODA and I. SHIMIZU,

29, (6), 657-665

CHEMICAL COMPOUNDS

Water Soluble cis-Platinum(I1) Com- plexes s. A. HAROUTOUNIAN, M. P. GEORGIADIS and J . c. BAILAR, Inorg. Chim. Acta, Bioinorg. Chem., 1986, 124, (b16), (3), 137-139 Extremely water soluble complexes of cis-Pt(I1) and 2-desoxystreptamine, D-glucosamine and 1-amino-z-methyl-2-propanol have been prepared; thus they may be less toxic than cis-DPP.


Crystal Growth of CsC1-Type Rh,,Al,,,Cu, from Copper Solution T. SHISHIW and H. TAKEI, J. Less-Common Met., 1986, 119, (I), 75-82 Single crystals of Rh,AI,-,Cu, (osxS9) have been prepared by the solution growth method, using Cu as solvent. The structure is the same as that of RhAl(CsC1-type) with space group B2.

ELECTROCHEMISTRY

The Electrochemistry of [PtH(PEt,),] +; Inverted and Amplified Cyclic Voltam- metric Waves and Catalytic Hydrogen Production at a Mercury Electrode

SOC., Dalton Trans., 1986, (6), 1225-1229

The electrochemistry of [PtH(PEt ,) , ] + at a Hg drop electrode has been investigated by cyclic voltammetry. The inverted and amplified waves in the voltammograms are interpreted by catalytic cycles for H, production from water. The sweeps of the voltammograms and variations in peak shape and position are discussed and interpreted. By sweeping anodically to - 1 . 7 V it has been possible to observe catalytic H, production over 1 6 hours, which cor- responds to an extremely efficient catalytic reaction with a turnover number of - 2 x Io’hour.

Characteristics and Stability of n-SilSnO, and n-Si/SnO,lPt Photoanodes

Electrochem. SOC., 1 9 8 6 , 133, (6), I I I ~ - I I I ~

The photoanodic behaviour of the SIS solid-state heterojunction n-Si/SiO,/SnO, was analysed in aqueous solution using various redox systems. The charge transfer at Ti/SnO, and Ti/SnO,/Pt inter- faces was determined, and for all the redox used, platinisation increased the heterogeneous rate constant by 1-2 orders of magnitude. Platinising n- Si/SnO, had no influence on JN curves when Fe(CN,)‘-/’- was used. The most dramatic improvement upon platinisation was with 1-D; and Fe I + / ’ + . The performance of the platinised photoanodes decreased with time.

Remarkable Enhancement of the Rate of Cathodic Reduction of Hydrocarbonate Anions at Palladium in the Presence of Caesium Ions M. SPICHIGER-ULMANN and 1. AUGUSTYNSKI, Helv. Chim. Acta, 1 9 8 6 , 69, (3), 632-634 Steady state polarisation curves obtained during electrochemical reduction of HCO: ions at a smooth Pd electrode, obtained in CsHCO, and NaHCO, solutions were compared. For x.oM CsHCO, the net current densities were up to 9 times larger than those observed in x.oM NaHCO, solution. The Cs+ cation may take part directly in the reaction at the cathode.

R. G. COMPTON and D. 1. COLE-HAMILTON, J. Chem.

D. BeLANGER, I . P. WDELET and B. A. LOMBOS, 3.

Anodic Characteristics of Amorphous Palladium-Base Alloys in Sodium Chloride Solutions N. KUMAGAI, A. KAWASHIMA, K . ASAMI and K. HASHIMOTO, J. Appl. Electrochem., 1986, 16, (4), 565-574 The anodic characteristics of a variety of Pd-based alloys were examined for use in dilute NaCl solutions at 3oOC. The corrosion resistance necessary for the Pd-metalloid anode was provided by alloying it with other platinum group metals and/or valve metals. Rh containing alloys showed high electrocatalytic activities for C1, evolution. Surface activation was necessary to achieve sufficiently high activities for C1 evolution at low overpotentials. The alloys had higher efficiency for Cl, evolution than existing anodes.

The Electrochemistry of Hexa- cyanoruthenate at Carbon Electrodes and the Use of Ruthenium Compounds as Mediators in the Glucose/Glucose Ox- idase System

troanal. Chem. Interfacial Electrochem., 1986, 206, (1

The reversible electrochemistry of the mediating cou- ple Ru(CN): -/Ru(CN): at graphite rod, pyrolytic graphite edge plane and glassy C electrodes for possible use in glucose sensors and fuel cells is reported. The use of Ru(CN)- and Ru(NH,),py’+ as mediators for the electrochemical oxidation of glucose oxidase in a glucose/glucose oxidase system is studied.

A. L. CRUMBLISS, H. A. 0. HILL and D. J. PAGE, J. Elec-

and 21, 327-331

PHOTOCONVERSION Optically Transparent Metallic Catalysts on Semiconductors A. HELLER, pure Appl. Chem., 1986, 58, (9),

Films consisting of 5nm Pt particles, which are substantially transparent, have been prepared by photoelectrodeposition of Pt onto p-InP under mass transport limited conditions. The resulting H evolv- ing photocathodes convert sunlight to stored energy with a 13% Gibbs free-energy efficiency.

Strikingly High Photovoltages of Photoelectrochemical Solar Cells Equip- ped with Platinum-Coated and Alkali- Etched n-Si Electrodes Y. NAKATO, H. YANO and H. TSUBOMURA, Chem. Lett. J P ~ . , 1986, (61, 987-990 The open circuit photovoltages, V,, of photoelectrochemical cells with a Pt coated n-Si electrode in aqueous redox solution have been increased by etching the Pt coat in alkali solutions. The maximum V, obtained was 0.685V, - I 5% higher than that on normal p-n junction Si solar cells (0.59V), indicating use as highly efficient solar energy converters.

I 189-1 192


Photoinduced Oxidation of Bromide to Bromine on Irradiated Platinized TiO, Powders and Platinized TiO, Particle9 Supported in Nafion Films R. DABESTANI, X. WANG, A. J . BARD, A. CAMPION, M. A. FOX, S. E. WEBBER and J. M. WHITE, 3. Phys. Chem., 1986, 90, (I2), 2729-2732 The photoelectrochemical oxidation of bromide ion in 0-saturated solutions of irradiated TiO, powders and TiO, in Nafion fdms with and without Pt was studied. K,PtBr, appears to form when platinised TiO, powder or platinised Ti0,-Nafion interact with oxygenated aqueous KBr in light or darkness. Br, formation occurs efficiently only after the Pt has been totally converted to PtBr, -. The TiO,/Nafion films produce Br, faster than TiO, powders.

Photo-Oxygenation of Alkylbenzenes by a Platinum Catalytic System A. MONACI, Gazz. Chim. Iral., 1986,116, (6), 339-340 Alkylbenzenes were photooxygenated under bub- bling air at room temperature in the presence of a PtN,S, complex as catalyst precursor. The wavelength of 254nm was effective for the reaction.

Water Photolysis over Metallized SrTiO, Catalysts K. YAMAGUTI and s. SATO, Nouv. J . Chim., 1986, 10, (4 and 9, 217-221 Gas- and liquid-phase water photolysis was carried out on metal-free and Pt or Rh loaded SrTiO, powders. Metal-free SrTiO, produced an amount of H , , but no 0 , . However the Pt or Rh greatly enhanced the H, production rate with accompanying 0, evolution. The Rh loading had higher photocatalytic activity than the Pt loading; maximum yield was - 1.2%. The effect of coatings of NaOH on metallised SrTiO, and metallised TiO, was also observed. Liquid-phase photolysis in I .oNNaOH or 0. I N H, SO, was significantly enhanced on reducing the thickness of the solution on the catalysts.

Interfacial Electron Transfer in Colloidal Metal and Semiconductor Dispersions and Photodecomposition of Water

Coord. Chem. Rev., 1986, 69, 57-125 An updated survey of literature on the photodecomposition of water is presented. The review is divided into sections covering photodecomposition in homogeneous dye-based systems using heterogeneous redox catalysts, homogeneous systems using homogeneous redox catalysts, heterogeneous redox catalysis, cleavage by U.V. and visible light in semiconductor-based systems and photochemistry and photoelectrochemistry in colloidal semiconductor systems. Platinum group metals contribute as sen- sitisers, catalysts and electrodes. Over 10% solar-to- chemical conversion efficiency for H, photogeneration is now achievable. (338 Refs.)

K. KALYANASUNDARAM, M. GMTZEL and E. PELIZZETTI,

Photocatalyzed Transformation of Cyanide to Thiocyanate by Rhodium- Loaded Cadmium Sulfide in Alkaline Aqueous Sulfide Media

ZETTI and M. BARBENI, h o r g . Chem., 1986, 25, (I3), 2'35-21 37 A process for totally disposing of CN- by photocatalytic transformation to SCN-, which is 1 0 0 times less toxic is described. The process uses a o.zwt.%Rh/CdS dispersion catalyst with light of A> 405nm or simulated AM1 solar radiation and an alkaline aqueous sulphide medium. H , is a byproduct. The quantum efficiency is

Efficient Photochemical Conversion of Aqueous Sulphides and Sulphites to Hydrogen Using a Rhodium-Loaded CdS Photocatalyst

BARBENI, J . Photochem., 1986, 33, ( I ) , 35-48 An efficient photocatalytic dispersion has been developed from C d S and a 0.2wt.% Rh(II1) salt via photodeposition. The catalyst is presumed to contain Rh species on the surface of the CdS particles, and can photocleave H , S in the absence and presence of SO, in alkaline media, to produce H, and S or H and S,O: -, respectively. The thermodynamic energy conversion efficiency is 0. I 7% or more.

Photoredox-Induced Polymerization of Microemulsion Droplets

Langmuir, 1986, 2, (3), 292-296 Photoinduced polymerisations in cetyltrimethylam- monium persulphate containing oil-in-water microemulsions were performed. Various monomers, including styrene, divinylbenzene, methyl methacrylate, etc., were polymerised highly efficiently under visible light by using Ru(bpy): + or eosin Y as a sensitiser. The morphology and size of the ag- gregates formed were examined.

E. BORGARELLO, R. TERZIAN, N. SERPONE, E. PELIZ-

0.25.

E. BORGARELLO, N. SERPONE, E. PELIZZETTI and M.

C. K. GMTZEL, M. JIROUSEK and M . GMTZEL,

Photogeneration of Carbon Monoxide and of Hydrogen via Simultaneous Photochemical Reduction of Carbon Dioxide and Water by Visible-Light Ir- radiation of Organic Solutions Containing Tris(2,2'-bipyridine)ruthenium(II) and Cobalt(I1) Species as Homogeneous Catalysts R. ZIESSEL, j. HAWECKER and J.-M. LEHN, Helv. Chim. Acta., 1986, 69, (9 , 1065-1084 CO and H, are generated simultaneously by visible- light irradiation of a system containing the [ Ru(bpv) , ] * + complex and a Co(I1) homogeneous catalyst, which mediate CO, and H,O reduction by intermediate formation of &(I), a tertiary amine as electron donor and an organic solvent. (64 Refs.)


LABORATORY APPARATUS AND TECHNIQUE Anodic Detection in Flow-Through Cells D. C. JOHNSON, 1. A. POLTA, T. 2. POLTA, G . G. NEUBERGER, J. JOHNSON, A. P.-C. TANG, I.-H. YE0 and J. BAUR, 3. Chem. SOC., Faraday Trans. I, 1986, 82, (4), 1081-1098 Progress in electrocatalytic processes for anodic detection in flowing aqueous solutions is discussed. Pulsed amperometric detection at Pt electrodes can sensitively detect the HCOOH groups in all alcohols, polyalcohols and carbohydrates, the N in amino acids and aminoglycosides, etc., and S in most inorganic and organic compounds. Detection at Pt is largely restricted to alkaline media. (85 Refs.)

Solid State Potentiometric Oxygen Gas Sensors W. C. MASKELL and B. c. H. STEELE, 3. Appl. Elec- trochem., 1986, 16, (41, 475-489 A review of recent literature on 0, sensors which are used in industry, internal combustion engines and in domestic appliances is presented. The sensors operate in the zero current mode and are based on 0 ion conducting solid electrolytes. Among sensors considered are ones with Pt electrodes and platinum group metal reference electrodes. (60 Refs.)

Variable-Temperature 195Pt NMR Spec- troscopy, a New Technique for the Study of Stereodynamics. Sulfur Inversion in a Platinum(I1) Complex with Methionine

0%. Ckem., 1986, 25, (141, 249-2433 The use of variable-temperature l n P t NMR spectroscopy for studying stereodynamics is discussed. It is uniquely suited to monitoring S inversion in the complex [ Pt(N-acetyl-L-methionine)Cl , ] -, and to studying dynamic processes involving relatively complex biomolecules and processes causing subtle changes in molecular structure, which are not easily followed by lH and "C NMR methods. Since the '9s Pt chemical shifts span a range greater than that of any other nucleus, they are highly sensitive to the nature of ligands and to subtle changes in molecular environment.

A New Method for Protection against Electrical Overheating Using a Sacrificial Coating and a CHEMFET Gas Sensor J. F. ROSS, C. I. TERRY and 8. C. WEBB, 3. Phys. E ,

A method using a urea-containing paint which liberates NH, on heating was used to detect overheating in an electronic system. A Pt gate MOSFET was used as the detector. The urea- containing paint/F't gate MOSFET was evaluated and could detect overheating of a resistor having a 0.025mm thick spray coat of the paint, at IOOOC.

D. D. GUMMIN, E. M. A. RATILLA and N. M. KOSTIC, In-

19863 19, (7), 536-540

An Integrated Hydrogen-Switching Sen- sor with a Pd-Si Tunnel MIS Structure

Sens. Aczuarors, 1986, 9, (z), 157-164 An integrated H-switching sensor has been made on a pn+ or np+ Si wafer by conventional means. The sensor has a MIS junction with a thin Pd fdm in series with a pn junction on the Si substrate. It can detect H, down to Ioppm or less at IOOOC and can close or open an electric circuit depending on H, concentration. It can thus act as an actuator. The transition time is within ~min at Iooppm and IOOOC.

Development of a Laboratory Cycle for a Thermochemical Water-Splitting Process (MelMeH Cycle)

PIETSCH and U. WINKELMANN, Inr. J . Hydrogen E ~ w , 1986, 119 (7)9 459-462 A metal-metal hydride process for splitting water using heat has been developed with a TiNi membrane separating the H acceptor from the electrolyte. Metals for use as membranes which have high H permeation rates, corrosion resistance to the electrolyte and long service life are discussed. Coated membranes Pd/Cu on Ta or Nb have high H permeation rates and long term stability, suitable for up to ~oo0C.

Applications of Novel Proton-Conducting Polymers to Hydrogen Sensing

Actuators, 1986, 9, (I), 1-7 Two types of H, sensors based on the PVA/H,PO, proton-conducting polymer electrolyte are examined. One is a solid state Pd hydride reference sensor and the other, which uses a gaseous reference source, has a self-supporting membrane with Pt electrodes on both sides. The ionic conducting polymer supports proton conduction down to -4oOC and has a cationic transfer number of I. The sensor could measure H, pressure (concentration) accurately and reproducibly from Io-'atm to Iatm, only CO and 0, affected its performance. Both sensors had a response time <6s and could operate over a wide concentration range.

Summary Abstract: A Hydrogen Plasma Diagnostic Based on Pd Metal-Oxide- Semiconductor Diodes R. BASTASZ and R. C. HUGHES, 3. vac. sci. Technol. A , 1986, 43 (31, Part 1, 629-630 When a PdMOS diode is used as a detector in H plasma or H ion beam, the energetic H ions striking the surface of the sensor are implanted into the device and bypass surface controlled steps. Energetic ions coming to rest in a thin Pd fdm at >zo°C diffuse quickly to the sensitive junction and are rapidly detected, thus PdMOS diodes should be useful as H selective monitors for monitoring the flux and possibly the energy of plasma ions.

M. OGITA, D.-B. YE, K. KAWAMURA and T. YAMAMOTO,

W. WEIRICH, B. BIALLAS, B. KUCLER, M. OERTEL, M.

A. 1. POLAK, S. PETTY-WEEKS and A. J. BEUHLER, Sens.


HETEROGENEOUS CATALYSIS

Immobilization of Colloidal Platinum Par- ticles onto Polyacrylamide Gel Having Amino Groups and Their Catalyses in Hydrogenations of Olefms H. HIRAI, M. OHTAKI and M. KOMIYAMA, Chem. Lett. %n., 1986, ( 9 , 269-272 Colloidal Pt dispersions are prepared and treated with polyacrylamide gel having amino groups, resulting in stable immobilisation of the Pt colloid onto the gel. This catalyst then exhibits high activities for olefm hydrogenations at 3ooC under Iatm.

Lead Tolerance of Noble Metal Catalysts for CO Oxidation T. CHANG and Y. s. SOHN, Bull. Korean Chem. SOC.,

The Pb tolerance of Pt/Al,O, catalysts was evaluated for CO oxidation depending on the properties of the Al,O, supports and base metals added as promoters. Promoters used were MnCl, .4H,O, SnC1,.5H,O, Fe(NO,),.gH,O and Cr(NOI),.9H,O, and base metals selected for incorporation into the Pt were B, Mn, V, Sn, Fe and 0. Among the four different Al,O, supports those with a large macropore volume (0.45 cm3/g) and 5% Ce showed the best resistance to Pb poisoning. Most of the base metals added to the Pt were ineffective for improving Pb resistance, but B has shown excellent Pb tolerance, although it decreases the initial catalytic activity.

Kinetics of the Reforming of C, Hydrocarbons on a Commercial PtRe/Al,O, Catalyst

Appl. Catal., 1986, 24, (1-2), 53-68 The kinetics of reforming C, hydrocarbons on a presulphided Pt-Re/Al , 0, catalyst between 627 and 776K and pressures 4.4-16.5 bars, with a H, partial pressure of 4-15.5 bars were compared with reforming on a Pt/Al,O, catalyst. At 723K the production rates and selectivities for iso-heptanes and aromatics from a C, feedstock are higher on Pt-Re than on Pt. The Re-Pt has a higher affinity for S than Pt, allowing Pt-Re/Al, 0, to operate under Sfree conditions without pronounced hydrogenolysis.

CO Oxidation on Pd/Al,O,. Transient Response and Rate Enhancement through Forced Concentration Cycling x. ZHOU, Y. BARSHAD and E. GULARI, Chem. Eng. Sci.,

The catalytic oxidation of CO over Pd/AI,O, was studied in a novel monolithic reactor with inside detection. The feed was periodically switched between CON, and O , N , giving time-averaged rates >40 times the maximum achievable steady-state rate. Map- ping the time-averaged reaction rates gave a unique global maximum at each temperature and flow.

1986, 7, (I) , 12-15

P. A. VAN TRIMPOW, G. B. MARIN and G. F. FROMENT,

1986, 4x9 ( 9 3 1277-1284

Palladium-Lanthanum Catalysts for Automotive Emission Control

Y. FUJITANI, Ind. Eng. Chem., Pmd. Res. Dev., 1986, 25, (2), 202-208 A Pd/La,O, was examined as a three-way catalyst in engine exhaust gas, simulated exhaust gas and for H , - NO, H,-NO-0,, CO-H,Oand propylene-H,Oreac- tions. &:fuel dependence of Pd/La,O, was similar to that of Rh, and the NO conversion during warm- up conditions was much better than that of Pd in engine exhaust control. The La,O, increases the activity and selectivity of Pd for NO reduction by H, , it increases the activities for CO and propylene reactions with H, 0 and also increases the amount of NO chemisorption.

H. MURAKI, H. SHINjOH, H. SOBUKAWA, K. YOKOTA and

New “PdAJltra-Thin Amorphous-Oxide LayerlZSM-5” Catalysts for Selective For- mation of Propane from CO/H, A. WE, K. A~AK~RA, c. EGAWA and Y . IWASAWA, Chem. Lett. Jpn., 1986, (6), 855-858 Three new types of the title catalyst, containing La,O,, SiO, or TiO, layers were prepared. The La,O, coated ZSM-5-supported Pd catalyst was selective for propane formation (68%) from CO and H, at 543K and I.oIMPa.

Silica-Supported Cationic Rhodium(1) Complexes as Hydrogenation Catalysts v. ZBIROVSK~andhi. EAPKA, Collect. Czech. Chem. Com- mun., 1986, 51, (4), 836-841 Cationic SiO, supported Rh(1) complexes prepared from Rh(COD)(acac) and phosphines of the type (C,H,O),Si(CH,),P(C,H,), (n= 1-3), in the presence of p-toluene sulphonic acid were found to be efficient catalysts for the hydrogenation of akenes, aka- dienes and Z-a-acetamidocinnamic acid at 4ooC and n o d H pressure. The most efficient catalysts had a PRh ration= 2. With this ratio for each molecule of the immobilised complex, the catalysts were 3-4 times more active than their homogeneous analogues.

The Effect of Chlorine in the Hydrogena- tion of Carbon Monoxide to Oxygenated Products at Elevated Pressures on Rh and Ir on SiO, and Al,03

PRINS, Appl. Catal., 1986, 25, (1-2), 43-50 The activities of Rh and Ir supported on SiO, and Al , 0 during the syngas reaction at elevated pressures were investigated. Rh was found to be more active than Ir and had a greater selectivity to higher hydrocarbons and C , -oxygenates. For Rh/SiO , high 0x0-selectivities were obtained (40%), while on C1 containing AI,O, this selectivity was rather low. When a Cl-free metal precursor was used or when the RhCl , /Al, 0, catalyst had special treatment, the 0x0-selectivities were rather high (30Yo).

B. J. KIP, F. W. A. DIRNE, J. VAN GRONDELLE and R.


Anionic Homo and Heterometallic Clusters Associated with Polymer- Supported Cations Catalysts for Alkene Hydroformylation: Evidence for a Bimetallic Synergistic Effect

and J.-P. AUNE, Nouv. 3. Chim., 1986, 10, (3), 159-163 Polymer supported M I , M, (M = Os, Ru) and RuOs , anionic clusters were catalysts for simultaneous hex-I-ene hydroformylation and isomerisation. The supported clusters were more active and selective than their soluble analogs. 0s clusters were more active than Ru clusters, but Ru clusters were more selective. The mixed metal cluster was more active than corresponding single metal clusters.

H. MARRAKCH, M. HAIMEUR, P. ESCALANT, J. LIETO

HOMOGENEOUS CATALYSIS The High Activation of (Ph,P),C = CH, by Palladium Acetate or Palladium Chloride towards Additions

L. SHAW, 3. Chem. SOC., Chem. Commun., 1986, (11), 882-883 Pd acetate very highly activates co-ordinated (Ph , P) , C = CH, towards additions to amines, hydrazines, amino acid esters, alcohols, phenols, thiols, acetylacetone and acetoacetic ester. PdCI, also activates, but less strongly. Pd(0Ac) , catalyses additions to the free ligand (Ph , P) , C = CH , . New Synthetic Reactions Catalyzed by Palladium Complexes J. TSUJI, Pure Appl. Chem., 1986, 58, (6), 869-878 Pd-phosphine complexes catalyse four reactions of allylic P-keto carboxylates. Decarboxylation- allylation -gives a-ally1 ketones, and decarboxylation- dehydrogenation in boiling acetonitrile gives a, 0- unsaturated ketones. The latter has been used as an industrial process for methyl jasmonate. Decarboxylation-deacetoxylatjon of a-acetoxyme- thyl-6-keto carboxylates gives a-methylene ketones. Decarboxylation-hydrogenolysis occurs. (43 Refs.)

A Novel Rhodium-Tri-N-Alkylphosphine Catalyst System for the Hydrogenation of Carbon Monoxide, Formaldehyde and Glycolaldehyde

Lett. Jpn., 1986, (3), 285-288 Syngas treatment of a mixture of a Rh compound of a large equimolar tri-n-alkylphosphine or tri(a- nonsubstituted alkyl)phosphine, and a solvent gives an orange yellow solution which is a highly active catalyst for CO hydrogenation to ethylene glycol and CH,OH. Similarly, formaldehyde and glycolaldehyde are hydrogenated to CHIOH and ethylene glycol, respectively, by the same catalyst.

A. M. HERRING, S. J. HIGGINS, G. B. JACOBSEN and B.

E. WATANABE, Y. HARA, K . WADA and T. ONODA, Chem.

Partial Hydrogenation of Benzene with Ruthenium Catalysts Prepared by a Chemical Mixing Procedure: Preparation and Properties of the Catalysts

SHIMIZU, s. IMAI and 1. IMAMURA, 3. Chem. Technol. Bwtechnol., 1986, 36, (9, 236-246 Ru catalysts were prepared in different alcohols by a chemical mixing technique and characterised by preparation of a homogeneous solution containing the catalyst components and then uniform coagulation of the solution through hydrolysis. This technique has potential for controlling the surface area of the catalysts and for making them porous. The catalysts prepared by this method were much more effective for the partial hydrogenation of benzene to cyclohexene in the absence of poisons, such as alkali metal hydroxide or transition metal sulphates.

S.-I. NIWA, F. MIZUKAMI, S. ISOYAMA, T. TSUCHIYA, K .

The Chemistry and Catalytic Properties of Ruthenium and Osmium Complexes. Part 4. A Comparative Study of the Reduction of Nitro Compounds under Hydrogen, Syngas and Water Gas

Catal., 1986, 36, (3), 283-291 The reduction of nitrobenzenes to the corresponding d i n e s is efficiently achieved by using a series of Ru and 0s complexes under H, , H , /CO and CO/H , 0 at moderate conditions. The reaction is best performed under water gas shift conditions in basic medium, in polar solvents. For monohydride catalysts, substitution of the aromatic ring by electron withdrawing groups results in lower rates and substitution by electron-releasing groups results in higher rates than the unsubstituted substrate, while the reverse is observed for dihydride species.

R. A. SANCHEZ-DELGADO and B. A. ORAMAS, 3. MOl.

FUEL CELLS Combined Electrochemical/Surface Science Investigations of Pt/Cr Alloy Electrodes

CAMPBELL, 3. Vac. Sci. Technol. A , 1986,4, (3), Part 11, 1617-1620 The role of G and its nature at the electrode surface was examined for C-supported PtG electrodes for 0, reduction in phosphoric acid fuel cells. Cyclic voltammetry in 85% phosphoric acid and X P S measurements are given. Electrodes with up to 40% G were stable up to + 1.6V vs. dynamic-H electrode. Intermediate 0. levels had G leached from the surface by + I .5V, leaving a porous Pt electrode with increased electrochemical H adsorption capacity. Pt,,,G,,, at >1.4V had Pt+' and G+6 species stabilised in a porous phosphate overlayer up to SOA thick. The Pt electrochemical H adsorption capacity simultaneously increased by a factor of IS.

K. A. DAUBE, M. T. PAFFETT, S. GOlTESFELD and C. T.


Platinum-Vanadium Carbon Supported Catalysts for Fuel Cell Applications G. CAMBANIS and D. CHADWICK, Appl. Catal., 1986, 25, (1-2), 191-198 Pt-V/C catalysts with various Pt:V ratios were prepared and reduced at several temperatures in N, , followed by characterisation which indicated Pt-V alloying. Activities for 0, electroreduction were measured at 18oOc in 100% orthophosphoric acid.

Methanol Electro-Oxidation and Surface Characteristics of Amorphous Pt-Zr Alloys Doped with Tin or Ruthenium

MASUMOTO, surf. Coatings Technol., 1986, 27, (4), 359-369 CH OH electrooxidation on amorphous Pt-Zr alloy electrodes doped with Sn or Ru were studied in 0.5 MH, SO, by potentiostatic polarisation and compared with surface characteristics. The electrocatalytic activity was considerably enhanced by brief treatment with aqueous HF, which yielded a porous surface layer on the electrodes. The layer was in a higher state of dispersion than ordinary Pt black.

Improvement of Palladium-Carbon Elec- trodes for Hydrogen-Oxygen Fuel Cell. 111. Preparing Methods of Hydrogen Electrode Catalysts Using Organic Palladium Complex M. UEHARA and T. SUZUKI, Denki Kagaku, 1986, 54, (4)> 347-351 A method of preparing highly active catalysts from bis-2-phenyl-~-allyl Pd chloride was examined. The catalysts prepared were examined for anodic activity at 3ooC in a half cell, and among other things it was concluded that to improve the dispersed adsorption an improvement in wetting the carrier surface was needed and for mild reduction of the complex the Pd complex should be added to almost freezing solvent. The catalysts obtained had 8 times the reactivity of usual Pd/C catalysts.

K. MACHIDA, M. ENYO, I. TOYOSHIMA, Y. TODA and T.

ELECTRICAL AND ELECTRONIC ENGINEERING

Pt-Si Contact Metallurgy Using Sputtered Pt and Different Annealing Processes

NINGHAM, F. E. TURENE, A. SUGERMAN and P. A. TOT- TA, J. Electmchem. Soc., 1986, 133, (6), 1256-1260 PtSi contacts were formed by different annealing pro-. cesses using sputtered Pt. Two annealing sequences and three annealing ambients for each annealing sequence are compared. A three-temperature sequence allows a complete reaction between Pt and Si, leaving a thin passivating oxide layer with excellent protection against etching in aqua regia.

C.-A. CHANG, A. SEGMULLER, H.-C. W. HUANG, B. CUN-

UHV-AES Investigation of Sulfur Sur- face Segregation in Precious Metal Wear Tracks 1. N. LLOYD, R. W. VOOK and L. E. POPE, IEEE Trans. Components, Hybrids, Manuf. Technol., 1986, C w T - 9 , (11, 92-96 Oscillatory sliding experiments in an UHV clean environment with Iatm He were performed on a Pd- base alloy pin on a Au-base alloy plate. The elements present in the wear tracks were measured by AES before and after several thousand cycles, and S was found which increased as the number of sliding cycles increased. The S partial pressure present in the He was < - I x 10-4torr, and it is concluded that S ori- ginates from the bulk of the alloys.

TEMPERATURE MEASUREMENT

A Cryogenic Temperature Controller with a Stability of k0 .03K over Several Days

(8), 594-597 The construction and operation of a temperature controller which has been used in the range 85-1o5K is described. A stability of -.o.o3K in space and time can be ensured for a continuous operation over several days. Calibrated Pt resistance thermometers were used together with suitable bridges for measurement and control. No vacuum is used in the set-up.

Amorphous Zr,,7Pd,,3 as a Temperature Reference Near 2.5K

K. SRINIVASAN and H. W. HECK, 3. Phys. E , 1986, 19,

N. MAENE, F. BIERMANS, J. CORNELIS, A. VAN DEN BOSCH and J . VAN SUMMEREN, Thennochim. Acta, 1986, 103, (I), 63-65 The superconducting transition temperature of high solidification rate material Zr0,,Pd,, was used as a temperature reference to estimate the temperature deviation between the thermometer and the sample in the pan of a vacuum microbalance with I O - ~ N sensitivity. The latter equipment belongs to a system for measuring magnetic susceptibilities at low temperatures down to 2.2K.

Temperature Measurement in High Pressure Cells Using a Rhodium+ 0.59'0Iron-Chrome1 Thermocouple Pair D. R . P. GUY and R. H. FRIEND, 3. Phys. E , 1986, 19, (6), 430-433 A thermocouple pair of Rh and 0.5at.%Fe-chromel provides usable sensitivity down to liquid He temperatures, for temperature measurement inside high pressure cells. The device has lowest sensitivity of -4pV/K at I ~ K , together with sufficient mechanical strength to withstand the handling necessary to assemble it inside the pressure cell.


NEW PATENTS

METALS AND ALLOYS Ornamental Platinum Alloy TANAKA KIKINZOKU KOGYO

Japanese Publ. Appls. 6 1 134, I ~ ~ l ~ l ~ l 6 l ~ l 8 l ~ An ornamental Pt alloy with excellent workability, mechanical strength and castability for jewellery applications contains 84-96% Pt, o.~-io%Co, and one or more of Rh, Ir, Ru, Au, Ag, Cu, Y, B, Ca, mischmetal, Fe, Mn, 0, Ni, etc.

Finely Powdered Noble Metal KAGAKU GIJUTSU-CHO KIN2

Japanese Publ. A p p 1 . 6 1 / 5 6 , 2 ~ Finely powdered metal for example, Pt, Ir, Rh, Os, Ru, Au, Ag, Re, for use in catalyses or electrical conductors is manufactured using a thermal plasma generated in N, or in N, and inert gas.

CHEMICAL COMPOUNDS Soluble Salt Production TANAKA KIKINZOKU KOGYO

Japanese Publ. Appl. 6116,129 The production of soluble salts of Ru, Ir andlor Rh by oxidising slightly soluble powder containing Ru, Ir, Rh andlor their oxides with a solution of alkali hydroxide and an oxidising agent, is claimed.

Transparent Iridium Oxide Preparation NIPPON KOGAKU K.K.

Japanese Publ. Appl. 61129,822 Transparent Ir oxide thin film is prepared on a substrate from Ir metal, and other metals by vacuum evaporation under low 0, partial pressure or by multi-component sputtering.

Antistatic Metallised Iron Oxide FUJI TITAN KOGYO K.K.

Japanese Publ. Appl. 61131,318 Iron oxides consisting of reduced micaceous Fe oxide is electrolessly coated with Pt, Pd, Au, Ni, Cu, or Cr. The oxides are useful as antistatic agents for rubber or plastics or electromagnetic wave shielding materials, or additives to ceramics for changing their electrical resistance.

High Purity Palladium Acetate Preparation MI'ISUBISHI CHEM. IND. K.K.

Japanese Pu bl. Appl. 6 I 147,440 Pd acetate is prepared by heating Pd powder in acetic acid in the presence of nitric acid, and then treating with an inert gas to remove the N containing impurity in the acetic acid. Trace N lowers catalytic activity.

ELECTROCHEMISTRY Electrodes for Electrolysis MITSUI ENG. & SHIPBUILD.

Japanese Publ. Appl. 601262,989 A C fibre electrode of large surface area carrying at least one of Pt, Pd, Ir, Ru, Au, Ag, Re, W, Cu, etc., its oxide and carbide, and being in contact with a diaphragm within an electrolytic cell, is claimed. The electrolytic voltage can be reduced, thus reducing side reactions and costs.

Electrolysis Electrodes T.D.K. CORP. Japanese Publ. Appl. 61152,38415 Sea water electrolysis is carried out by electrodes coated with Pt-Ir alloy and oxides of Ir and Ru, or with a mixture of Ru oxide, Ir oxide, Pt and Sn oxide. The electrodes have good resistance to corrosion, and good characteristics, especially in low temperature sea water.

Anode for Brine Electrolysis

A Ti anode covered with RuO,, COO and TiO, (with RuO,:TiO, = I : 2-4) has increased corrosion resistance for sea water electrolysis.

Insoluble Anode G. F. POTAPOVA Russian Patent 1,171,566 Insoluble anodes 2-3pm thick are obtained when a low voltage gas phase arc-spark discharge is used to coat a Ti or Ta support with Pt, producing a Ti-Pt or Ta-Pt layer. They have more chemical resistance.

A.S. U.S.S.R. FAR-E CHEM. Russian Patent 1,139,770

ELECTRODEPOSITION AND SURFACE COATINGS Palladium Electroplating Process AMERICAN TEL. & TELEG. CO.

World Patent Appl. 861652A A Pd electroplating bath for electronic applications consists of an organic ammine or ammonia complexed Pd hydroxide. The complex Pd ammine hydroxide has high solubility in water, eliminating danger of precipitates forming during the plating process.

Platinum Photodeposition MITSUBISHI CHEM. IND. K.K.

Japanese Publ. Appl. 61150,633 Pt is deposited from Pt halides, especially chloroplatinates, onto an inorganic semiconductor by light irradiation of a semiconductor in aqueous solution, containing a metal halide and a reducing agent. The semiconductors are used as catalysts or gas sensors. Dense deposition of fmal Pt particles is ensured.

Platinum Metals Rev . , 1986, 30, (4), 211-215 21 1

Rhodium Plating Electrolyte A S . UKR. GEN. INORG. CHEM.

Russian Patent I , 174,496 A Rh plating electrolyte of increased stability is prepared by repeated precipitation of the hydroxide, filtration, dissolution in concentrated H , SO, and sulphamic acid addition. Crack-free coatings up to I 5 pm thick can be prepared.

Palladium Plating Bath C. Z. BATZIN Russian Patent I, I 78,803 Improved electrodeposition and coating quality are obtained during Pd plating by using non-dissolvable electrodes and an anion exchange membrane between the cathode bar and the cation exchange membrane.

LABORATORY APPARATUS AND TECHNIQUE Gas Detector TOSHIBA K.K. British Appl. 2,166,549A A gas detector comprises an In-Sn oxide thin film covering the electrodes, and a laminated catalyst layer containing preferably one or more of Pt, Pd and Rh supported on AI,O, of thickness lo-Soprn. The detector can detect reducing gas in air with high sensitivity and selectivity, especially CO, C, CH, and C,H,.

Oxygen Sensor Electrode HITACHI CHEMICAL K.K.

Japanese Publ. Appl. 61117,950 Hexachlorplatinic acid was applied to the Pt surface of a baked yttria stabilised ZrO, electrolyte and used to detect 0,. The adhesion of the metal and electrolyte is strong and long lasting.

Platinum Crucible FUJI PHOTO FILM K.K. Japanese Publ. Appl. 61/24,982 A crucible made of Pt or Pt alloy has a nozzle for discharging molten material. It can be used for manufacturing ferrite powder for magnetic recordings.

Crucible for Single Crystal Growth

A columnar crucible for growth of high quality large single crystals of Mn-Zn ferrite is made of Pt or Pt-Rh with reinforcing wires of Pt-Rh at the upper end of the crucible.

HITACHI METAL K.K. Japanese Publ. Appl. 61126,588

Oxygen Analyser AZERB. AZIZBEKOV PETROCHE.

Russian Patent 1,176,230 An electrochemical 0, analyser for analysing 0, and H, containing gas has separate gas cells and a Pd foil which allows H,, but not 0,, to pass through. 0, is ionised in one cell and the current flowing through a load resistor measures the 0, concentration.

JOINING Palladium Solder TANAKA KIKINZOKU KOGYO

Japanese Publ. Appl. 61120,697 A Pd solder with high corrosion resistance and low melting point of 700-800~C comprises 5-30wt.Oh Ag, o.25-7wt.%Si7 o.5-2owt.%Ga andlor Ge and balance Pd. The solder can bond Ti or Ti alloy members together, or to Cu, Ni, stainless steels, etc.

Soldering Bump NIPPON TELEG. & TELEPH.

Japanese Publ. Appl. 61 146,052 A soldering bump with strong bonding strength, for use in electronic devices, such as Pb-based Josephson elements, is formed from two intermediate metal layers of Pd, Au, Cr or Cu.

HETEROGENEOUS CATALYSIS Fruit Preservation JOHNSON M A m E Y P.L.C. British Appl. 2,163,637A Ethylene gas is removed from stored fruit and vegetables by withdrawing the air, heating it and passing it through a catalytic combustor with a catalyst containing one or more of Pt, Pd, Ru or Rh on activated Al. The air is then returned to the store.

Preparation of Pyridine IMPERIAL CHEMICAL INDUSTRIES P.L.C.

British Appl. 2,165,844A Pyridine is prepared by a one- or two-stage hydrogenation of I ,3-propane dinitrile(I1) over a Pd/SiO, catalyst. The catalyst preparation is given. The process is preferably one-stage when a 1-100 times stoichiometric excess of H , is used.

Platinum Catalyst for Carbon Monoxide Conversion IND. RES. INST. OF JAPAN British Appl. 2,166,061A A process for the production of a CO conversion Hydrogen Electrolyser

A S . UKR. GAS INST. Russian 1,172,945 catalyst containing at least 6mgIgC for the efficient Increased H, purity is obtained from a filter-press electrolyser with a perforated bipolar electrode main sheet. The cathode sheet is a Pd-Ag alloy which is non-permeable and porous to H , to give improved separation.

conv&sion to COiat room temperature under humid conditions, is claimed. The catalyst is prepared by dipping activated C in chloroplatinic acid solution, drying, reducing, then treating with H,O,. The activated C can additionally be treated with a monomer.


Hydrocracking Catalyst UNION OIL c o . CALIFORNIA European Appl. 172,578A A hydrocracking catalyst with controllable water content giving high and consistent activity is based on a Y zeolite exchanged with Pd or Pt cations and rare earth cations.

Shale Oil Treatment COMMONWEALTH SCIENT. ORG.

World Patent Appl. 8611,743A A catalyst for the I-step hydrocracking and hydrotreating of shale oil comprises Ru/zeolite with a Group VI and/or a Group VIII metal on a refractory support. The catalyst can deal, in I-step, with high- boiling feeds such as heavy crude, coal and tar sands.

Catalyst for Hydrocarbon Synthesis EXXON RES. & ENG, co, U.S. Patent 4,567,205 A Ru-Re/TiO, catalyst is used for hydrocarbon synthesis from CO-H, mixtures. High quality middle distillate fuels are produced. The catalyst has high activity and low CH, and CO, selectivities, and the deactivation rate is reduced.

Catalyst for Ammonia Synthesis M. W. KELLOGG CO. U.S. Patent 4,568,532 NH, is produced from synthesis gas over a Fe catalyst and over a RuIC catalyst by recycling.

Alkane Dehydrogenation ATLANTIC RICHFIELD CO. U.S. Patent 4,568,789 A C, + alkane is dehydrogenated to the corresponding olefm and water by contacting with a reducible oxide of Ru and at least one alkali or alkali earth metal, or compound. The reduced Ru oxide can be reoxidised and reused. The alkali metal increases the selectivity to dehydrogenation products.

Alkene Preparation PHILLIPS PETROLEUM co. U.S. Patent 4,570,025 Alkenes are prepared by hydrogenating one or more unsaturated hydrocarbons over a PdIAl phosphate catalyst where A l : P = o . 4 - 1 . 1 : I. The catalysts are more active andlor selective than known catalysts and give high yields of (cyc1o)alkenes.

Lead-Resistant Catalyst SIGNAL APP. TECHN. IN. U.S. Patent 4,572,904 A Pb-resistant exhaust gas catalyst comprises a protective zirconia coating over Pt, Pd, Ir and/or Rh on a refractory inorganic oxide support. The activity is retained even with fuel containing 0.01 g A Pb.

Tertiary Amine Manufacture MITSUBISHI PETROCH. K.K.

Japanese Publ. Appl. 601258 ,145

Tertiary amines containing two long alkyi groups are prepared by reacting olefin@, CO, H, and primary amines in the presence of a Rh and Ru compound catalyst in a one-step reaction.

Ethyl Acetate Production MITSUBISHI GAS CHEM. K.K.

Japanese Publ. Appl. 6 1 15,050 Ethyl acetate is produced in 95% yield from acetic anhydride and H, in the presence of supported Pd andlor its compounds, and sulphonic acids.

Preparation of 2-Fluoropropanol SAGAMI CHEM. RES. CENTRE

Japanese Publ. Appl. 6117 ,228

2-Fluoropropanol is formed by hydroformylation of monofluoroethylene in the presence of a supported Group VIII metal compound such as a Pt, Rh, Ru or CO catalyst. Catalysts such as hexarhodium hex- adecacarbonyl on activated C, SiO,, Al,O,, or organic polymer in amounts 10-106 moles/CH,CFH are used at 8ooC and a CO pressure of 35 atm and H, pressure of 35 atm, with toluene, to give 2-fluoropropanol in 95% yield.

Exhaust Gas Purification TOYOTA JIDOSHA K.K. Japanese Publ. Appl. 61118,439 A monolithic catalyst is produced by repeated immer- sion of the support and base material into a solution of Pt, Pd, Ir, Ru, Rh, Os, Cr, Ni, V or Cu, so that more catalytic material is loaded onto one end. The catalyst has improved durability and activity.

Reforming Catalyst TOKYO GAS K.K. Japanese Publ. Appl. 61128 ,451

A Ru catalyst on a solid sintered support is used for steam reforming of methane, natural gas, liquid propane gas, naphtha or in a fuel cell system. No free C is generated.

Combustion Catalyst BABCOCK-HITACHI K.K.

Japanese Pu bl. Appl. 61 128,453 A catalyst with high activity at lower temperatures, for example for the combustion of CH, , is made by loading a support of, for instance, y-Al,O, with ( I ) Pd and/or Rh, and (2) Ba, Sr or Ca.

Exhaust Gas Purification MITSUI MINING & SMELTING

Dewaxing Lubricating Oil Japanese Publ. Appl. 61 /28,45 5 TEXACO INC. u.5 Patent 4 ,5759417 A honeycomb support carrying Pt, Pd or Rh and also A catalytic dewaxing process for a hydrocarbon base Ni oxide is used as a three-way catalyst for the lubricating oil involves passing it over a calcined H purification of combustion exhaust gas. The catalyst mordenite catalyst with a SiO, :Al,O, ratio removes 8 0 9 0 % CO and HC at higher temperatures 10-50 : I , loaded with Pt or Pd. than catalysts without Ni oxide.


Production Catalyst for Ethanols AGENCY OF IND. SCI. TECH.

Japanese Pu bl. Appl. 6 I 130,541 A supported Rh-Fe catalyst is prepared by adding Fe as an accelerator to the Rh. The amount of 2C compounds produced by CO and H, can be increased without increasing the amount of CH, formed. Selec- tivity to ethanols is >70%.

Double Oxide Combustion Catalysts MATSUSHITA ELEC. IND. K.K.

Japanese Publ. Appl 61133,232 A catalyst A , -,A’,BO,, where A is an alkaline earth metal, A‘ is Ce or Sr, and B is Rh, Pt or Ru, supported on AI,O, or SiO,, is used in small combustors for burning the lighter hydrocarbons at 700-800OC.

Methane Combustion Catalyst NIPPON SHOKUBAI KAGAKU

Japanese Publ. Appl. 61133,233 A catalyst for CH, combustion at lower temperatures comprises Pt, Pd and Ni on stabilised Al,O,, TiO, or ZrO, . CH, is burned over the catalyst to heat up further fuel gas to its combustion temperature. This is used in gas turbine generators, heat recovery boilers, etc., enabling clean exhaust to be produced.

Air Purification NIKKI UNIVERSAL K.K.

Japanese Publ. Appl. 61135,853 Catalysts for purifying the air of CO from automobile ventilators, air conditioners, fans, waste gas from stoves or water heaters, tunnels and underground garages consist of Ptly-Al,O,, with Fe, Co, Ni, Mn, Cu, Cr, Sn, Pb or Ce deposited on it. The catalyst gives a 97% CO conversion rate.

Three-Way Catalyst NISSAN MOTOR K . K . Japanese Publ. Appl. 61/46,247 A three-way catalyst giving conversion rates >go% at lower temperatures, such as 4m0C, is made by loading Pt and Rh salts onto a support and calcining in a combustion exhaust gas stream.

Engine Exhaust Purification TOYOTA JIDOSHA K.K.

Japanese Publ. Appl. 61146,252 A monolithic catalyst for exhaust purification with improved activity (74%HC, 84%CO and 82%NOx removal at 350°C) is formed from a columnar base material with micropores, such as cordierite, on which is deposited Pt, Pd, Ir, Ru, Rh, Os, etc.

High Calorific Value Gas KANSAI NETSU KAGAKU

Japanese Publ. Appl. 61157,242 A catalyst of Pt, Pd, Rh, Ir, Ru on Fe group metal substrate, with oxides of Mo andlor W on AI,O, and/or SiO, support is used to produce a high calorific value gas from H, and CO.

Exhaust Gas Purification TOYOTA JIWSHA K.K.

Japanese Publ. Appl. 61161,642 An engine exhaust purification catalyst has a columnar monolithic body with micropores holding AI,O, loaded with catalysts of Pd, Pt and Rh. The catalyst can remove almost 100% CO at 300OC; and also needs less catalyst material.

Hydrogen Rich Gas Production SHELL INT. RES. Mii . B.V. French Appl.2,567,866 A H, rich gas is prepared by reacting CO with steam in the presence of a Cu and/or Pd/spinel catalyst.

Ethylene Glycol Preparation BASF A.G. German Offen. 3,427,138 Increased yields of ethylene glycol are produced from CO and H, under increased temperatures and pressures with a Rh-Co catalyst of metals or their car- bony1 complexes, salts or oxides, where Rh : Co is 20: I to 60 : I .

Active Agent Evaporator GLOBOL-WERK c . m . b . H . German Offen. 3,436,310 Insecticides, bactericides, disinfectants, etc., are evaporated from an impregnated porous plate by a flameless burner containing a finely distributed Pt catalyst.

Battery Catalyst VARTA BATTERIE A.G. German Offen. 3,437,479 A catalyst for recombining H, and 0,, in an ac- cumulator, for instance in submarines, is made from PTFE, activated charcoal and acetylene black with the Pd catalyst in the core zone. This battery eliminates the need to collect the battery gases.

Palladium-Silver Catalyst BASF A.G. German Offen. 3,438,851 A Pd-Ag/Al, 0, catalyst is used in the preparation of sterically pure olefmically unsaturated compounds, by hydrogenating the corresponding acetylenically unsaturated compound.

Sulphur Oxide Gettering Agent W. R. GRACE CO. Australian Patent 8946,146 A gettering agent for removing SO, from flue gases, and giving a reduction of >go% SO, emissions from catalytic cracking comprises metal sulphate, preferably MgSO, and AI,O,, together with a Pt andlor Pd catalyst.

Aromatisation of Gasoline Fractions A.S. KAZA PETRO-CHEM. Russian Patent I , I 15,464 A method for the production of high octane gasolines and aromatic hydrocarbons giving improved yields and quality of products involves contacting the starting products with H, over a Pt-B-Co-Cr/Al,O, catalyst at 410-528OC and atmospheric pressure. The reaction products are contacted with Pt-B-W/AI,O, .


Trans-Retinol Production A.S. KAZA ORG. CATALYS. Russian Patent 1,141,710 Trans-retinol, an intermediate for vitamin A production, is prepared by hydrogenating retinol in the presence of an Ir-BalAl,O, catalyst. Adding Co to the catalyst increases the productivity.

FUEL CELLS

Oxygen Reduction Electrode NATIONAL RES. DEV. CORP.

World Patent Appl. 8611,642A An 0, reduction electrode for use in a fuel cell, which only produces very low amounts of H, 0 , , consists of a conductive substrate with a catalyst of Ru oxide or a macrocyclic metal derivative, when used at cathodic potentials, produces very little H,O,.

CORROSION PROTECTION

Coated Metal Life Estimate NIPPON PAINT K.K. Japanese Publ. Appl. 61154,437 A method to estimate the service life of anticorrosion coatings for steel marine structures, ships, bridges, plants, pipelines, etc., on site, subjects the coating to I-IOOV using an opposing electrode of Pt, C, etc., to measure times before current start up.

GLASS TECHNOLOGY Molten Glass Stirrers TOSHIBA K.K. Japanese Publ. Appl. 61136,123 Glass stirrers with excellent high temperature strength are formed with Mo as main component, coated with a heat-resistant intermediate layer, then with a Pt containing material.

ELECTRICAL AND ELECTRONIC ENGINEERING

Electroconductive Fibrous Articles AGENCY OF IND. SCI. TECH.

European Appl. 174,183A The production of electroconductive fibrous articles involves soaking fibrous articles in a Pd hydrosol containing a surfactant and then metal plating. The articles are used in electromagnetic shields.

Sealed Contact Relay A.T. & T. BELL LABS. U.S. Patent 4,573,030 The sealed relay has a catalytic metal of at least one metal selected from Pt, Pd, Ir, Rh, Ru, Os, Ni, Co and Fe, on the rubbing surface which polymerises organic matter into a solid polymer. The contacts have long life and low contact resistance.

Ceramic Wafer for Electronics NIPPON KOATSU DENKI

Japanese Publ. Appl. 61146,088 A ceramic wafer made of Al oxide, B oxide, SiO,, alkali metal oxide and RuO,, Rh,O,, F e , 0 3 , NiO, etc., is produced at a comparatively low temperature. A conductive paste of Pt, Au-Pt, etc., is printed onto the wafer. The wafers produced have excellent mechanical and electrical characteristics.

MEDICAL USES

Diamine Platinum Complexes CHUCAI SEIYAKU K.K. European Appl. 176,005A New diamine Pt complexes are useful anti-tumour complexes and have low toxicity; they have greater activity than Cisplatin.

Anti-Tumour Platinum Complexes JOHNSON MATTHEY P.L.C.

Japanese Pu bl. Appl. 61 /I 5,892 An anti-tumour Pt co-ordination compound with lower toxicity is prepared by reacting ammonium trichloride with KI, and then with AgNO, and dicar- boxylic acid.

Platinum for Tooth Polishing Y. NAUAGAWA Japanese Publ. Appl. 61127,916 TiO, powder incorporating Fe,O, n-type semiconductor, carried on a good conductivity metal, especially Pt, is used to clean teeth and the inside of the mouth. The Fe,O, has a photocatalytic effect.

Organo-Platinum Anti-Tumour Complexes MITSUI PETROCHEM. IND. K.K.

Japanese Publ. AppLC. 61137,794/95196 New organo-Pt anti-tumour complexes can be ad- ministered parenterally or orally as injections, sup- positories, ointments, tablets, capsules or syrups against leukaemia, lung cancer and melanoma.

Surgical Implants I. BLAETnER Swiss Patent Appl. 654,738 Surgical implants and repair plates are made from steel coated with Cu then with Rh, Pd, Ag or Au.

Electrodes for Blood Purification ELECTROCHEM. INST. Russian Patent 1,175,494 Two Ti electrodes promoted with Pt are used in blood treatment during dialysis for detoxifying the organism. The electrodes carry current at a density of 11.2-5.6 mAIcm,. This method obviates the need for additional physico-chemical treatment.

The New Patents abstracts have been prepared from material published by Derwent Publications Limited.

Platinum Metals Rev. , 1986, 30, (4) 215

AUTHOR INDEX TO VOLUME 30

Page Adamiec, J. 204 Aita, C. R. 38 Akimoto, Y. 44 Al-Emara, K. 98 Aliwi, S. M. 98 Allen, R. V. 129 Anderson, T. G. 98 Andriollo, A. 45, 151 Andzelm, J. 147 Antler, M. I40 Anton, R. 204 Aoyama, Y. 151 Appleby, A. J. 196 Arakawa, H. 44 Armgarth, M. 99 Asakura, K. 208 Asami, K. 148, 205 Aspnes, D. E. 20 Aubert, A. E. 13 Augustynski, J. 205 Aune, J.-P. 209 Auvray, P. 204 Aygen, S. 151

Babenko, V. P. 96 Baboian, R. 63 Bailar, J. C. 204 Ballini, Y. 204 Barbeni, M. 206 Bard, A. J. 40, 206 Barnard, C. F. J. 116 Barshad, Y. 208 Bastasz, R. 207 Basu, S. 96 Baur, J. 207 Baykara, N. A. 147 Baykara, S. Z. 147 Bilanger, D. 205 Bell, A. T. 99, 151 Benedek, R. A. 130 Berthier, S. 41 Besley, L. M. 46 Bettelheim, A. 42 Beuhler, A. J. 207 Bevk, J. 21 Biallas, B. 207 Biermans, F. 210 Bilitewski, U. 97 Bischoff, K. B. 151 Blum, Y. 45 Bocarsly, A. B. 41 Boguszewska, Z. 98. 152 Borbidge, W. E. 129 Borgarello, E. 149, 206 Bose, D. N. 96 Boudart, M. I29 Boutaine, J. L. 99 Braca, G. 44 Brett, N. H. 147 Brewer, K. J. 147 Brodzki, D. 151 Broitman, F. 42

Bugli, G. Byvik, C. E.

Cacciola, G. Calvert, H. Cambanis, G. Cameron, D. S. Cameron, R. E. Campbell, C. T. Campion, A. Eapka, M. Carpenter, J. E. Carter, S. Ceriotti, A. Chadwick, D. Chaldecott, J. A. Chang, C.-A. Chang, T. Charcosset, H. Chen, H. S. Chinakov, V. D.

Page 151

I I

174 I I7 210

73 41

209 206 208 150 1 I9 39

210 29

210 208 23 96 96

Cho, B. K. 42, 150 Chun Yu, B. C. 149 Clarke, F. J. J. 21 Claus, H. 61 Cleare, M. J. I I6 Cole-Hamilton, D. J. 205 Collins, J. P. 45 Collins, P. M. D. 141 Compton, R. G. 205 Cook, R. L. 40 Cornelis, J. 210 Corti, C. W. 79, 184 Cottington, 1. E. 1 I I 13,

20. 27. 62, 84, 129, 130, 166, 182, 195

Couch, N. R. Crumbliss, A. L. Cunningham, B. Cunningham, J. E. Czarkie, P.

Dabestani, R. Dalla Betta, R. A. Danielsson, B. Dannetun, H. M. Da Prato, P. Daube, K. A. Davenas, J. De Dios Mpez-

GonzPez, J. De Visser, A. Della Mea, G. Delouise, L. A. Demartin, F. Dickson, R. S. Dietrichs, J. Dirne, F. W. A. Dobos, K. Dodelet, J. P. Doi, Y.

147 205 210

39 45

206 I29 99 43 44

209 I66

151 38 38 39 39 28

204 208 42

205

Dombek, B. D. Dzhur, E. A.

Eckenrode, J. P. Ector, H. Edamoto, T. Edelstein, J. Edwall, G. Egawa, C. Ege, D. Eguchi, T. Elliott, C. M. Emeren, di. Enna, G . 4 . Enoeda, M. Enyo, M. Equey, J.-F. Erdohelyi, A. Escalant, P. Eskilosen, S. S. Espidel, J.

Farina, M. Farrauto, R. J. Felberg, J. D. Fendler, J. H. Fleming, E. Flint, S. A. Flynn, C. P. Fox, M. A. Franks, C. Franse, J. J. M. Frkhet, J. M. J. Friend, R. H. Frings, P. H. Frischat, G. H. Froment, G. F. Fujihara, M. Fujikawa, K. Fujisawa, T. Fujita, F. E. Fujitani, Y. Fujiwara, R. Fukui, M. Fukuma, T. Fukuoka, H. Fukushima, T. Furuhama, S. Furuuchi, Y.

Ganzeria, R. Garcia, E. Y. GenescC, J. Georgiadis, M. Geselowitz, D. Ghosh, P. K. Gibson, J. F. Gilbert, J. A. Giordano, N.

Page 45 99

96 13

148 96 97

208 40 38 97 41 39 42

210 40

100 209 41 45

99 I97 99 41 98 96 39

206 I19 38 43

2 10 38

204 208 152 I48 151 38

151, 208 204 151 152 I52

44, loo I52 45

44 38 80

P. 204 147 40

I I9 147 I74

Page Gonzalez, R. D. 42 Gottesfeld, S. 209 Gough, K. G. I68 Gousseau, G. 99 Gratzel, C. K. 206 Gratzel, M. 40, 98,

149. 206 Graziani, M. 44 Greatbatch, W. I20 Greenbaum, E. 97 Groppe, J. V. 46 Gruenenfelder, N. 43 Gryaznov, V. M. 68 Gu, B. 40 Gu, C.-L. I49 Guerin, R. 204 Guerrero-Ruiz, A. 15 I Gulari, E. 208 Gummin, D. D. 207 Gupta, B. 99 Guy, D. R. P. 210

Hackerman, N. 149 Hagiwara, M. 96 Haimeur, M. 209 Haines, H. R. 147 Hakimifard, D. 43 Hamada, T. 38 Handley, J. R. 12 Haouzi, A. 148 Hara, M. I48 Hara, Y. 209 Harata, M. I40 Harding, J. T. I97 Harmer, M. A. 40 Haroutounian, S. A. 204 Harrap, K. R. 1 I6 Harth, R. 42 Hartley, F. R. 83 Hashimoto, K. 148, 205 Hawecker, J. 206 Hawk, W. J. I49 Hayashi, T. 41 Hayfield, P. C. S. 158 Headley, G. W. 96 Heck, H. W. 210 Heck, R. F. I83 Heller, A. 20, 205 Herring, A. M. 209 Herz, R. K. 43 Hessler, D. 41 Hettrick, M. C. 96 Hexter, R. M. 43 Heywood, A. E. 130 Hidai, M. I52 Higgins, S. J. 209 Higo, A. 38 Hill, E. W. 38 Hill, H. A. 0. 40, 205

Hine, F. 96 Hilleke, R. 0. I50

44 Gonzdlez, E. 45 Hirai, H. 44. 149. 208

Platinum Meials Rev., 1986, 30, (4), 216-218 216

Page Hiraki, H. I40 Hirota, N. 41 Hoffman, G. R. 38 Hoffman, M. 2. 41, 149 Hori, K. 100 Hruby, V. 2 Huang, H.-C. W. 210 Hughes, R. C. 207 Hunt, L. B. 72 Hiipl, K. 204 Hurkx, G. A. M. 46 Husain, A. 99

Ichikawa, M. Ichimura, K. Ilan, A. B. Imai, S. Imamura, J. Ingman, F. Inokuchi, T. Inoue, A. Inoue, N. Inui, T. Inukai, T. Ip, W. M. Ishii, H. Ishii, Y. Ishikawa, H. Isoyama, S. Ives, N. A. Iwafune, %-I. Iwakura, C. Iwane, G. Iwasawa, Y. Izumi, Y.

44. 100 98

I96 209 209 97

148 96 98

150 204 99 42

100 148 209 46 44

148 I52

131, 208 100

Jackson, S. D. Jacobsen, G. B. Jagur-Grodzinski, Jamison, P. L. Jegamariadassov,

G. D. Jiao, F.-Y. Jin, D. Jirousek, M. Johnson, D. C. Johnson, J. Jones, R. Josquin, W. J. M. Joubert, J. C.

Kagiya, T. Kahan, D. J. Kaizu, Y. Kalyanasundaram,

Kaneko, M. Kapusta, S. Karpeles, R. Kase, A. Kawamura, K. Kawashima, A. Kawate, S.4. Kelly,-P. F. Kemp, R. C. Kemp, W. R. G.

14 209

J. 152 96

151 44 I50 206 207 207 147

. J. 46 148

97 147 39

206 I49 149 99

208 207 205 204 39 46 46

K.

Page Kera, Y. 45 Kessler, R. 2 Kinoshita, E. 97 Kip, B. J. 208 Kirchheim, R. 38 Kirsch- De Mesmaeker, A. 98

Kita, H. 40, 148 Kiwi, J. 40, 98

Knifton, J. F. 45, 100 Knecht, W. 43

Kobayashi, H. 39 Kobayashi, K. 39 Kobayashi, T. 152 Kach, T. A. 197 Komiyama, M. 208 Konobas, Y. J. 79 Kosonacky, W. F. 46 Kostld, N. M. 207 Kotoh, K. 42 Koyanagi, N. 96 Koyasu, Y. 152 Kramer, P. W. 40 Kramer, R. 152 Krasiejko, M. 98. 152 Kudo, K. 100 Kiigler, B. 207 Kuhnert, L. 98 Kukushkin, Y. N. 198 Kumagai, N. 205 Kushida, K. I52

Kuwabara, A. 149 Kuwano, N. 38

Kusy, A. 204

Lafait, J. 41 Lammertsma, K. 99 Lang, J. F. 147 Larkin, J. A. 21 Lehn, J.-M. 206 Lenarda, M. 44 W n , V. 45 Leung, M. S. 46 Leyland-Jones, B. I19 Li, C.-L. I49 Li, D.-G. 44 Li, N.-H. 43 Lieto, J. 209 Likholobov, V. A. 96 Lintz, €I.-G. 43 Lloyd, J. N. 210 Liiftler, D. G . 38, 99

Lmngoni, G . 39 Lombos, B. A. 205

Lundstrom, I. 43, 99

Machida, K. MacIntyre, J. E. Mackor, A. Maclay, G. J. Maeda, M. Maene, N. Maetens, D. Majni, G. Makino, Y. Manassero, M. Mandal, K. C.

210 72 41 42

148 210 98 38

150 39 96

Page

Manoharan, R. 100 Marchionna, M. 39 Margerum, L. D. 40 Marin, G. B. 208 MBrquez-Silva,

R.-L. 151 Marrakch, H. 209 Martinelli, P. 99 Marvin, D. C. 46 Masel, R. I. I47 Maskell, W. C. 207 Massalski, T. B. 38 Masumoto, T.

96, 148, 210 Matsuo, T. 39 Matsuoka, M. 204 Matsuzaki, T. 44 Mazumdar, D. 96 McAlister, A. J. 147 McCabe, A. R. 54 McCabe, R. W. 150 McClure, D. J. 148 McCready, D. F. 150 McCreery, R. L. 39 McCullough, A. M. 38 McEvoy, A. J. 98 Medina, M. 151 Melhotra, A. K. 99 Menovsky, A. 38 Metcalfe, I. S. 150 Meyer, T. J. 40, 147 Miles, A. I I Milisavljevic, B. 43 Mills, G. A. 151 Minami, 1. I52 Mingos, D. M. P. 96 Misono, M. 44 Miyake, H. 44, 97 Miyama, H. 149 Miyamoto, A. 150 Mizukami, F. 209 Monaci, A. 206 Montgomery, C. M. 147 Morgan, H. I50 Mor, U. 42 Mori, S. 100 Moriyama, H. 97 Motoo, S. 45, 196 Muller, J. 148 Miiller, K. 67 Munakata, K. 42 Muraki, H. 151, 208 Murota, J. 42 Murphy, W. R. 147 Murray, R. W. 40

Manogue, W. 151

Nagai, M. Nagura, T. Nakajima, H. Nakano, Y. Nakato, Y. Naman, S. A. Nanjundiah, C. Nasielski-Hinkens, Natsushita, S. Neal, A. H.

42 44

I48 152 205 98 40

R. 98 44

197

Nekipelov, V. M. Nenov, I. P. Neuberger, G. G. Nierlich, F. Nishikawa, M. Nishimoto, S.4. Nishimura, S. Niwa, S. 1. Nosaka, Y. Nunes, P. P.

Obenaus, F.

Oertel, M. Ogita, M. Ogoshi, H. Ogura, K. Oh, S. H. 42 Ohta. H. Ohtaki, M. Ohtani, B. Okahata, Y. Okamoto, H. Okazumi, F. Oki, K. Okuhara, T. Olah, G. A. Onda, Y. Ono, K. Onoda, T. Oramas, B. A. Osaka, T. Osaki, H. Oshima, R. Osterholm, J.-E. Ottaviani, G.

O’Toole, T. R.

oda, s.

Ott, D.

Paccagnella, A. Paffett, M. T. Page, D. J. Palmowska-KuS, 8.

Pande, N. K. Parker, W. L. Parmaliana, A. Parnell, D. G. Pebler, A. Peckham, M. Pelizzetti, E. 149, Petersen, J. D. Petersson, L . 4 . Pethig, R. Petty, S. Petty-Weeks, S. Peuckert, M. Phala, H. Piersma, B. J. Pietsch, M. Piva, G. Polak, A. J. Polta, J. A. Polta, T. 2. Poosittisak, S. Pope, L. E.

Puge 96 42

207 I50 42 97 44

209 149 15 I

I50 204 207 207 151 99 . 150 39

208 97 39 38

I so 38 44 99

100 204 209 209 41 97 38 40 38

I32 40

38 209 205 98, I52 99 43

I74 I47 100 I I8 206 147 43 I50

2 207 I29 100 I20 207 39

207 207 207 152 210


Page Porter, J. D. 20 Postlethwaite,

M. A. J. 131 Potter, P. E. 147 Prasad, D. R. 41, 149 Pratt, A. S. 54 Prins, R. 208 Pszonicka, M. 96

Quinn, T. J. 74

Rabette, P. M. 166 Raevskaya, M. V. 79

Ramberg, L. 98 Ramesh, K. V. 45, 100 Ratilla, E. M. A. 207 Raub, C. J. 132 Ray, J. D. 43 Reber, J.-F. 148 Redepenning, J. G. 97 Redon, A. M. 41 Rieck, J. S. 151

Roach, P. R. 150 Robson, G. G. 146 Rodriguez-Ramos, 1. 151 Rodriguez-Reinoso, F.

151 Rose, T. L. 40 Ross, J. F. 207 Ross, P. N. I96 Rubel, M. 96 Rudolf, P. 201 Runck, R. J. 196 Ruppert, R. 45

Rahamim, Y. 45

Rippin, D. 43

Rusek, M. 148 Russell, M. J. H. 183

Sacharoff, A. C. 27 Saito, T. I40

Sakurai, H. 46 Salahub, D. R. 147 Sammells, A. F. 40 Sbnchez-Delgado,

R. A. 42, 151, 209 Sansoni, M. 39 Sarma, B. K. 150 Sarode, P. R. 100 Sato, S. 206 Sauvage, J. P. 45 Sbrana, G. 44 Schoneich, H.-G. 97 Schreiber, H. D. 96 Schuette, S. A. 39 Secoue, M. 204 Segmiiller, A. 210 Seki, T. 39

Saito, Y. 97

Sella. C. 41 Serpone, N. 149, 206 Settle, F. A. 96 Seymour, R. J. 167 Shallcross, F. V. 46 Shaw, B. L. 209 Sheng, T. T. 20

Page Shimizu, I. 204 Shimizu, K. 209 Shinjoh, H. 208 Shinoda, S. 91 Shinouskis, E. J. 43 Shishido, T. 205 Shukla, A. K. 45, 100 Shvo, Y. 45 Siedle, A. R. 43

Smith, 1. I18

Soga, K. 44

Sokolova, 1. G. 79 Solymosi, F. 100

Spetz, A. 99

Spoliarich, R. 44

Srinivasan, K. 210

Stamp, W. L. 100

Smith, G. D. W. 54

Sobukawa, H. 208

Sohn, Y. S. 208

Speitling, A. 38

Spichiger- Ulmann, M. 205

Spurlin, S. R. 147

St. John, M. R. 40

Steele, B. C. H. 207 Stevens, G. T. I50 Stkkel, D. 61 Stokes, J. I30 Stolz, u. 38 Strydom, I. Le R. 195

Subramaniam, B. 99

Sudo, H. I52

SuSrez, M. P. 99

Sudhakar, C. 43

Sugerman, A. 2 10 Sugi, Y. 44

Sugita, N. 100 Sugimoto, S. 38

Sugiura, T. 148 Sugiyama, M. 38 Sundaresan. S. 150

Swiatek, Z. G. 197 Szokefalvi-

Nagy, A. 38

Szymanski, R. 23

Suzuki, T. 210

Szpytma, A. 204

Taguchi, K. 39 Takagi, K. 152 Takahashi, T. 44, 149 Takahashi, Y. 42

Takano, Y. I50

Takei, H. 205 Takeishi, T. 42 Takeuchi, H. 152 Takeuchi, K. 44 Takikawa, 0. 140 Takuma, K. 39 Talsi, E. P. 96 Tamura, H. 44. 148 Tanaka, J. 62 Tanaka, Y. 100 Tang, A. P.-C. 207

Takamagari, K. 99

Takayasu, K. 97

Page Tanguy, J. C. 99 Taube, M. 43 Tebai, L. 42 Telluchea, C. 99 Terry, C. 1. 207 Terzian, R. 206 Tetrick, S. M. 39 Thewissen,

D. H. M. W. 41 Thompson, D. T. 28,

83, 166 Tiller, A. J. 40 Timmer, K. 41 Tinnemans, A. H. A. 41 Toda, Y. 210 Toi, H. 151 Tombbcz, 1. 100 Torii, S. I48 Toshima, N. 44, 149 Totta, P. A. 2 10 Toudic, Y. 204 Toyoshima, 1. 210 Tran Khanh Vien 41 Tricot, Y.-M. 41 Trivedi, N. J. 99 Trzeciak. A. M. 151 Tsubomura, H. 205 Tsuchiya, T. 209 Tsuji, J. 152. 209 Turene, F. E. 210

Uchida, Y. 152 Uda, M. 44 Uehara, M. 210 Uosaki, K. 40 Urabe, K. 100

Vadimsky, R. G. 20 Valencia, N. 45, 151 Valentini, G. 44 Van Den Bosch, A. 210 Van Der Zouwen-

Assink, E. A. 41 Van Eldik, R. 151 Van Grondelle, J. 208 Van Summeren, J. 210 Van Trimpont, P. A. 208

Vanderwalker, D. M. I47

Vanhumbeeck, J. 41 Vannice, M. A. 43 Varma, A. 99 Vasudevan, S. 100 Verhoeven,

J. F. C. M. 46 Victori, L. 80 Villani, T. S. 46 Vining, W. J. 40 Vook, R. W. 210 Vrtis, M. L. I50

Wada, K. 209 Waddell, G. H. 62 Walsh, M. P. 106

Walters, R. P. Walton, R. A. Wang, X. Wardle, R. W. M. Watanabe, E. Watanabe, K. Watanabe, M. 45 Watanabe, T. Webb, B. C. Webber, S. E. Weirich, W. Weisker, T. Wells, A. Wells, P. B. West, L. A. Westervelt, R. M. Westmoreland,

Whelan, P. T. White, H. S. White, J. M. White, J. R. Whitlaw, K. J. Wibberley, B. L. Wilkinson, G. Wiltshaw, E. Winkelmann, U. Winograd, N. Winquist, F. Wissmann, P. Woerlee, P. H. Woollins, J. D. Wright, M. K.

T. D.

Xie, W.-J.

Yamada, A. Yamada, M. Yamaguti, K. Yamakawa, T. Yamamoto, K. Yamamoto, T. Yang, M.-X. Yang, S.-K. Yano, H. Yano, N. Yasuda, H. K. Ye, D.-B. Yeo, I.-H. Yin, Y.-Q. Yokota, A. Yokota, K. 151 Yokota, M. Yoneda, R. Yoneda, T. Yoshimura, T.

Zbirovskf, V. Zhang, Y.-M. Zhou, X. Ziessel, R. Zimmer, G. Ziolkowski, J. J. Ziichner, H.

Page 197 39

206 96

209 98

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I95 14

150 21

40 129 148 206 40

150 I68 1 I6 I I7 207

39 99

204 46 39

196

44

149 152 206 97 38

207 I49 44

205 96 40

207 207 44 44

, 208 45 40

I29 100

208 I49 208 206 42

151 97


SUBJECT INDEX TO VOLUME 30

a=abstract Page Acetal, formation, a 44 Acetic Acid, production from syngas, a 100 Acetylene, production from benzene

43 Acid Rain I l l Adsorption, CO, NO, 0, on Pt(210). a I47

H in fuel cell electrodes, a 209 HI on Pt, Pd, Rh on Cr,O,. a 204 NO on Rh{lll}, Rh{331], a 39

207 42

using Rhlu-Al , 0 J , a

Alcohols, detection in flowing solutions, a ethyl, oxidation on Pt,Ru,Pt-Ru,Pd,Rh/SiO,, a

methyl, electrooxidation on doped Pt-Zr production from syngas, a 44

electrodes, a 210 I50 oxidation on Pt wires, a

production by platinum metals, a 43, 99, 100. 209

I 0 0 I52

synthesis of methyl formate, a oxidation bv Ru catalvsts. a < .

primary electrooxidation, a 148 secondary, photo conversions, a 41

production from syngas, a 151 secondary, electrooxidation, a I48

Aldehydes, photoproduction from alcohols, a 41 oxidation. indirect, by redox system, a 148 production from alcohol oxidation, a I52

from syngas, a 151 Alkanes, ethane, hydrogenation 23

43 I50

Alkenes, ethylene, hydrogenation over

methane, formation from syngas, a propane, conversion to aromatics, a

IRu,H(CO),,I~-SiO,, a 44 hydrogenation, by Rh(I)complex/SiO, , a linear, oxidation by AcOPdO, , a propylene, oxidation in catalytic converter. a

208 96 42

synthesis from alkyne, a 100 Alkylation, amines, photocatalytic, a 97 Alkylhenzenes, photooxygenation, a 206 N-Alkylformamide, production, a 45 Alkynes, hydrogenation to alkenes, a 100 Amines, additions to, by (Ph,P),C=CH,, a 209

photocatalytic preparation, a 97 Ammonia, biosensor, a 99

207 for HCN acid synthesis on Pt, a 99

168

detection to show electrical overheating. a

oxidation, high pressure test rig reaction with syngas to form

N-alkylformamides, a 45 Aniline, production, a 209 Aromatics, from propane, novel catalyst for, a 150

Barium Ruthenate, printing head Batteries, for Greenwich time signal, history Benzene, conversion to acetylene, a

Biomedical Engineering, International Symposium Biosenson, of NH,, Ir or Pt MOS. a Bonding, Pt to Ti, characteristics, a

reaction, metals to ceramics Book Review, Dictionary of Organometallic

Compounds, First Supplement

hydrogenation 23,

Homogeneous Catalysis with Compounds

Palladium Reagents in Organic Syntheses Platinum Metals Cluster Catalysts Science of Precious Metals, Japanese Supported Metal Complexes-Catalysis Tailored Metal Catalysts, polymer protected

Borane, reactions, modified by Rh porphyrin. a Bridges, corrosion protection of Bromine, formation, on Pt/TiOl powder, a

of Rhodium and Iridium

I40 29 43

209 13 99 99

I29

72

28 I83 166 62 83

131 151 158 206

Page Cancer, anti-tumour drug, "Paraplatin" I I6 Carbon Oxides, CO, adsorption on Pt(210), a 147

adsorption, hydrogenation over 44

chemisorption on 0 s clusterhpport 14 detection by MOSFET, a 42

hydrogenation 23 over Ir, a 100. 208 over Pd/support. a 43, 151, 208 over Rh, a 45, 151. 208, 209 over Ru , a 44, 45. 151

208 42, 43. 150, 208

206 43

I 5 I 40

151

100 209 I66

heterogeneous, a 42, 43, 44, 99. 100. 150, 151. 208, 209

homogeneous, a 44. 45. 100, 151. 152, 209 28

iridium complexes, book review 28 metal complexes, book review 83

I50 43, 99. 106, 150. 208

I3 I 42

shift reaction, a 45 97

208 100

Ru + additives/Al , 0 J , a

emission control, U.S. experience 106

CH, synthesis, a 100

photogeneration from CO,, HIO, a

oxidation, over lead tolerant catalysts, a

reactions with 0,. NO, over Rh ribbon, a

over platinum metals, a

with Rh(acac)iP(OPh), 1 , , a CO,, electroreduction to CO, a

hydrogenation over Ru/C black, a photoreduction with HIO, a 206 synthesis of methyl formate, a

Carboxylates, allylic 8-keto, new reactions, a Catalysis, clusters in, book review

by Rh, Ir compounds, book review

Catalysts, automotive, exhaust, CO oxidation, a

colloidal, polymer protected, book review converters, pellet mobility on poisoning, a Iridium Complexes, Ir(1)-diimine,water gas

Ir/AI,O,, SO, , CI effect, syngas reaction, a

Ir-Fe-Ir-Ti/SiO,, for ethanol synthesis,

Osmium Complexes, aldehyde, ketone

three-way

Ir-Sn, photocatalyst for dehydrogenation, a

IrlSiO, +Fe, for CO hydrogenation, a

from syngas, a 44

hydrogenations, a 151 reduction of nitro compounds, under

[OsH(Br)(CO)(PPh,), 1, preparation, activity. a IH,Os,(CO),,I~, water gas shift reaction, a 0s carbonyl clusters/AI,O,, SiO,, TiO,,

0s clusten/polymer, for hydroformy lation,

Os,(CO) ,,/zeolite, water gas shift reaction, a Palladium, black, activity, acetal formation, a

PdCI,, (Ph,P),C=CH, additions, a Pd(OAc),, (Ph,P),C=CH, additions, a Pd-SiO,-Si, for H,O production from

Palladium Alloys, H permeable, for drugs Palladium Complexes, bis-2-phenyl-~-allyl

Pd, highly active H electrode, fuel cell, a

H , ,H,/CO.COIH ,O. a

reactions

isomerisation, a

0 2 - H 2 atmospheres, a

Pd phosphines, allylic 0-keto carboxylate reactions, a

Pd/AI,O,, cycled CO oxidation. a Pd/AI,O,, tritium oxidation, a Pd/AI,O,, PdIC, mlyunsatured hydrocarbons

hydrogenation, (1' Pt/Pd/Rh/AI,O, ,-/Ce/AI,O,, automotive, a Pd-rare earthla-Al,O,, NO reduction, a PdlBaSO,, CH, halogenation, a PdlC, soybean oil hydrogenation, a Pd/La,O,, three-way, automotive, a

209 45 44

14

209 44 44

209 209

43 68

210

209 208 42

I50 43

151 99 43

208


Catalysts (conrd.) Page Pdllanthanide rare earth oxide, CO

hydrogenation, a 43 PdCl , lpolybenzimidazole, nitro compounds

reduction, a 43 PdlSiO,, C,H,OH oxidation. a 42 PdlSiO,, promoted, syngas reaction, a 151 Pdlultra thin La,O,, S O , , TiO,lZSM-S,

syngas reaction, a 208 Platinum, blacks, activity, acetal formation, a 44

in a-Fe,O, photoanodes, a 40 in H energy system I74 PI ion-exchanged Ga silicate, a I50 Pt-Mg-TiO, , for U.V. water-splitting, a 98 Ph-Rh, bimetallic, three-way, automotive. a 150 wire, methanol oxidation, a 150

96 Pt-Rh gauze, NH, oxidation I68

reconstruction 54

photoconversion of alcohols, a 41 PtN , S , , alkylbenzene photooxygenation, a 206

208 CO oxidation, a 150 converters, poisoning, pellet mobility. a 42

tritium oxidation, a 42 PtIPd/Rh/AI,O,, -/CelAI,O,, automotive, a 43

43 sulphided, C , reforming, a 208

Pt/CdS, H, photoproduction, a 41. 148 Pt-VIC, in fuel cells, a 310 Pt-ZrlC,-ZrO,, preparation, characterisation 23 Pt colloidlgel, olefin hydrogenation, a 208 Pt colloidlpolymerised micelle, H , Pt-PV*+, for H, evolution, a PtlSiO,, Pt-RulSiO,. C,H,OH oxidation, u

PtlTiO,, effect of T on HI photoevolution, a

colloidal, preparation, activity, a 44

Platinum Alloys, Pt-Pd-Rh,Pt-Pd-Rh-Ru. gauze, 0, reaction with, a

Platinum Complexes, H , PtCl d ,

Pt/AI,O,, +additions, Pb tolerant, a

halogenation of CH,, a 99

Pt-RelAl,O,, in H, burning engine, a

Pt-Rhly-Al,O,, three-way, a 99

photoproduction, a I49 I49 42 206 98

in alcohol, amine preparation, a 91 particles, H, photoproduction, a 40 powder, Bioxidation, a 206

cyanide photooxidation I I . 40

PtlSrTiO, powders, water photolysis, a

Pt colloidlthylakoid membranes,

PtlYSZ, CO oxidation, a I50 Platinum Metals, water photodecomposition.

literature review, a 206 clusters, book review 166

Platinum MetalslCr,O,, H, adsorption, u 204 Platinum Metal Complexeslsupport,

book review 83 Rhodium, polycrystalline ribbon, for CO

oxidation, NO-CO. NO-CO-0, reactions, a 43 Rhodium Alloys, Rh-Pd-Pt, Rh-Pd-Pt-Ru,

gauze, 0, reaction with, a 96

Rhodium Complexes, book review 28 Rh. Ru complexes, CO hydrogenation, a 45 Rh(acac) [P(OPh),],, reactions with

H,, CO, olefins, a 151 Rh,(CO), ,, Rh,(CO), 6 , hydroformylation

Rh-tri-N-alkylphosphine, syngas reaction, a 209 RhCI(PPh,), , methyl formate synthesis, a 100 RhCI(PPh,), + Li salts, hydrogenations, a 100 (PPh,), polyacrylate Rh(l), crosslinked, a 44 rhodium porphyrin. modifying borane

photosynthetic, a 97

Rh-Pt gauzes, reconstruction 54

activity, a 44

. - reactions, h 151

RhlAI,O,, S O , , CI effects, syngas reaction, a 208

151 Na-Rh/Al,O, , CO hydrogenation, a

Catalysts (conrd. ) PtlPdlRhlAl,O,, -/CelAI,O,, automotive. a Rhla-Al,O,, benzene conversion, a RhlCdS, dispersion, cyanide disposal, a RhlCdS, in dihexadecyl phosphate, H,

photoproduction, a 5. for H.S ohotocleavaee. a

hydrocracking soybean oil, u TiO, promoter, for NO reduction, a

Rh(1) comDlexeslSi0,. cationic hydrogenation

Page 43 43 206

41 206 42 151 99

~- of alkenis, a 208

RhlSrTiO, powders, water photolysis. a 206 Rhlsupport, syngas conversions. trifunctional, a 151

100 Ruthenium, alcohol oxidation. a 152

melt. N-alkvlformamide oroduction. a 45

Rh-Ti-Fe-IrlSiO,, ethanol production, a 44

Rh + PtlTiO,, CH, synthesis, a

in alcohols. chemical mixing procedure, a 209 CO, CO, hydrogenation, a 151

hydrogenations. u 151 Ruthenium Complexes, aldehyde, ketone

-rediction of nitro compounds. under H,. H,/CO, CO/H,O. a 209

Ru + Rh complexes, I promoted, CO

Ru(bpy,)f+, in Belousov-Zhabotinsky hydro enation. a 45

reaction. a 98 in photopolymerisation, a 206 on photoelectrode. a I49

[Ru(bpy),l*+ + Co(1l)complex. H,O. CO, photoreduction, a

EDTA/(Ru(bpy):+/MV'+, colloidal Pt. HI 206

photoproduction. a I49

assessment, a 41. 149 Ru(bpz) :+/MV * +/EDTA, system

Ru,(CO) ,,, N-alkylformamide

Co,(CO),-Ru,(CO) , 2 . olefin production, a 45

I52

alkyne hydrogenations. a

photocatalyst, a Ru-tris-( I ,4,5,8-1etraazaphenanthrene).

Ru/AI,O,, + additions, CO hydrogenation, a Ru-Co-1lBu.PBr melt, for CH ,COOH

45

98 44

formation. u 100 151 I49

photoproduction, a 41

RulC black, CO, CO, hydrogenations, a Ru0,lCdS + AI,O,, H, from H , S , a RuOJCdS, powder, preparation, H,

Ru clustenlpolymer, hydroformy lation. isomerisation, a 209

RuO, lpolypyrrole, photocatalysts, u I49 RulSiO,, C,H,OH oxidation, a 42 [Ru,H(CO),,]-ISiO,, water gas shift reaction. a 44 RuO,/Y zeolite + Fe0,lY zeolite,

photocatalysts, a I49 RuO, IVS, RuO,lVS, aqueous, photocatalyst. a 98

Cathodic Protection, impressed current I58 miniature 63

Cells, electrolysis, CH, conversion to CHIOH, u 99 galvanic, seawater treatment, a 40 photoelectrochemical, with Pd, RuO, -modified

electrodes, a 41 Ceramics, reaction bonded to metals 129 Cermets, Pt-AI,O,, coatings, properties. a 41 Charge Coupled Device, i.r., F'tSi Schottky

barriers, in, a 46 Chemicals, ultra pure, production 68 Chemisorption, CO, 0, by 0 s clusters 14

I47 Chlorine, evolution from NaCI, a 148, 205

97 97

H, , on Pd clusters, a

Chloroplasts, platinised, H, photoevolution, a Chromium, electroplating, by anodes, a


Page Claddings, Pt, in composites 132 Clusters, in catalysis, book review I66

2 Coatings, Pd, electroless, a I49

Pd-Ni, new HCI electrolyte, a 42 Pt on Cu, Ni alloys I32 R-AI,O, cermets. properties, a 41 PI black, low reflectance 21 protective, for refractories, conference report 196

Commodities, Annual Meeting, Inst. Mining & Metallurgy I66

Concrete, reinforced, corrosion prevention in 158 Conference, Biomedical Engineering 13

Chemistry of Platinum Group Metals. Sheffield 1987 I I9

Fuel Cells 73 “Paraplatin”, anti-cancer drug 116 Precious Metals, Tenth International 196

current system 63 reinforced concrete, impressed current I58

I2 Crystals, Rh,,AI,,.,Cu, growth, a 205

Coal, used in MHD generators

Corrosion, protection, miniature impressed

Crucibles, Ir, for crystal growth

Ru-Ir superlattice. a 39 single, TiO,, platinised, electrode, H,.O,

photocatalytic transformation by RhlCdS. a

evolution, a 40 Cyanide, photooxidation by platinised T i0 , 1 I , 40

206 Cyclohexene, reactions, a 152, 209

Dehydrogenation, propan-2-01, photocatalytic

Detectors, ammonia, biosensors, a by Sn-lr, a

CO. by PdO-Pd MOSFET. a electrical overheating by Pt-gate MOSFET, a glucose, electrodes for, a HCOOH groups, in flowing solutions. a H , , by resistance strain gauge, a

Pd MOS, a Pd filmlpn-SilMIS. a Pd hydride reference, a proton conducting polymer, a

H plasma, H ions, PdMOS diode, a N in amino acids, aminoglycosides, a 0,. literature review, a S . in compounds, in flowing solutions, a

Diffusion, H, through Pd clusters, a Pt into Ti, solid phase bonding, a PdMOS. in H plasma detector, a

Divinylbenzene, photopolymerization, a Dobereiner, Johann Wolfgang, history Drugs, “Paraplatin” anti-cancer

Electrical Contacts, Pd, S effects on wear, a

ultra pure. production

Pd-Ni Pd plated, fast process, a InlPtlGaAs, a PtSi, preparations, a

thin Pd films, a

production by MHD generators

Electrical Resistivity, Ir, Pd, Rh, W wires, a

Electricity, extraction from salt gradients, a

Electrocatalysis, Ta-, Ti- platinum metals alloys Electrochemistry, a 39, 40, 97. 148, Electrodeposition, a 41, 42, 149.

Pd, high speed, for contacts, a Pd-Ni, Au flashes, electronic contacts, a

new HCI electrolyte, a Ru, from LiCI-KCI melt, a

Electrodes, anode. impressed current, corrosion protection

Pd-Ir-P, CI, evolution, a Pd-Rh, CI, evolution, a Pt plate, CH, conversions, a

96 99 42 207 205 207 96 .. 42 207 207 207 207 207 207 207 I47 99 207 206 141 I16 68

210 67 41 46 210 38 204 152 2

I20 205 I50 41 149 42 42

63 148 205 99

Electrodes (conrd.) Page 100

PtlTi, with I r 0 2 for Cr electroplating. a 97 C, +Ru(CN):-/Ru(CN):, electrochemistry. a 205 cathodes, PtlC, fuel cells I29 11-0, , cyclic voltammetry of redox proteins. a 40 Hg drop [hH(PEt,) , l+ behaviour at, a 205 montmorillonite +Os(bpy):+, Ru(bpy):+,

Fe(bpy):+lPt, glass C, SnO,lglass, electrochemistry. a 40

Pd, CsHCO, reduction, a 205 80

Pd, proton injection into solid sample, a I50 Pd-C, from organic Pd complex, in fuel cell. a 210 photoanodes. Fe oxideln-Si, modified with

Pd. RuO,, in photoelectrochemical cell, a 41 Pt in a-Fe,O, , a 40 n-SilSn0,lPt +Fe, a 205

205 207

in organic detectors, a 207

Pt-AI. for seawater desalination. a 40 h-SPE. electrochemical behaviour. a 148 h-Zr. amorphous, doped, methanol

oxidation, a 210 Pt silicide gate, ultra small, a 46 PtlBi,Ru,O,. for O1 evolution, a I48 h l C , in phosphoric acid fuel cell, a 100

PtlC, H,. fuel cells, preparation, a

dissolution in acidic chloride solutions PdlPdO, pH sensing, a 97

photocathode, Ptlp-InP, H ? evolution. a h. in H sensor, a

in magnetohydrodynamic generators 2

microdisk, in voltammetry, a 39

coconut-shell, charcoal, in fuel cells, a hlactive CIC cloth, in energy production. a Ptlglassy C. for fuel cells, a Pt-CrlC. in phosphoric acid fuel cells, a PtlKF felt, in fuel cell, a Pt thin filmlmica, a Pt/Re(4-vinyl-4‘-methyl-2.2‘-bipyridine)

(CO,)Cl, CO, reduction, a Ptln-Si, in solar cells, a PtlSn, in organic fuel cells, a PtlTiO, , electrochemical behaviour. a Ru(bpy): + +. Prussian bluelgraphite.

tris(5,5 ’-dicarboxyester-2,2’-bipyridine)Ru.

RuO,, thin film, cyclic voltammetry of redox

photoproperties. a

electrochemical response, a

45 I52 I52 209 45 I48

40 205 45 40

I49

97

proteins, a 40

aldehydes, a I48 41. 98

80 41. 42

97

43. 99, 150, 208 U.S. experience I06

I52 206

using Ptln-Si electrodes. a 205 using RuS, electrodes, a 41

transmission as H I74 43

Ethylene Glycol, production, a 45. 209 Esters, production, a 151 Ethers, production, a 151

RuO,/RuO, redox, electrooxidation of alcohols.

RuS,, crystalline, photoproperties, a Electrodissolution, Pd in acidic chloride

Electroplating, Cr, by platinised Ti anode, a Emerson, Peter H., platinotype prints

Electrolytes, for Pd plating, a

Emission Control, automotive, a

Energy, extraction from salt gradients, a solar, conversion, literature survey. a

I 82

Engines, H,-burning. for trucks, a H , , 2-stroke diesel, with Pt ignition, a 152

Ferrocene, detection using Pt electrodes, a Films, Pt transparent 20

39

h-0, optical properties, a 38 207

45, 100, 152, 209, 210 electrodes for 45, 100, 129, 210 formic acid, a 45 phosphoric acid, characterisation. a 100. 209

Fire, detector, electrical overheating, a Fuel Cells, a

Platinum Metals Rev., 1986, 30, (4) 22 1

Fuel Cells (contd.) conference Techmart Exhibition

Page 73. 196

I67

Gauzes, Pd-Ni. for Pt,Rh recovery in HNO, plant, a 100

Pt, for Ag separation from Cu, a 152 Pt-Pd-Rh,Pt-Pd-Rh-Ru. reaction with 0,. a 96 Pt-Rh, NH, oxidation 100, 168

54

Glass, for nuclear waste immobilisation, a 96 204

Glucose, sensor, mediators for, a 205 Greenwich Time Signal, history 29 Grinberg, Alexander Abramovich, history I98

Halogenation, CH, over Pt/AI,O,, Pd/BaSO,, a 99 Helium, low temperature cooling, Pt powder for, a 150

204 Heptanes, production from C, hydrocarbons, a 208 Heterojunction, n-Si/SiO,/SnO,, platinised + Fe, a 205 I-Hexene, hydroformylation, a 44. 152 Hex-l-ene, hydroformylation, isomerisation.

simultaneous, a 209 History, discovery of catalysis, DBbereiner 141

Greenwich time signal 29

Rh-Pt, reconstruction after NH, oxidation Generators, magnetohydrodynamic 2

Glasses, metallic, PdNiP, He solubility in, a

solubility in PdNiP glass melts, a

A. A. Grinberg, P? co-ordination compounds platinotype prints, Emerson’s Pt-lr, kilogram standard Standard of light

Hot Water Storage Tanks, corrosion protection Hydrocarbonate, anions, reduction at Pd

Hydrocarbons, C , , reforming over sulphided electrode +Cst, a

Pt-Re/Al,O,, a C , -C? , production from syngas conversions, a emission control, U.S. experience polyunsatured, hydrogenation, a

Hydrocracking, soybean oil. a Hydrocyanic Acid, synthesis from NH, and CH,

on Pt, a

hex-I-ene. a Hydroformylation, olefins, a 44.

198 182 74 84 63

205

208 151 I06 150 151

99 I52 209

Hydrogen, activation of Pt gauze, for AglCu separation, a 98

209 204

chemisorption, diffusion on Pd clusters, a 147 detector 42. 96, 207 electrochemical evolution at platinised TiO,. a 40 energy system I74 engine, ignition in, a 152 H, -0 , atmospheres, for H , 0 production, a 43 implanted, efect on Pd,Si. a 38

97 oxidation in catalytic converter. a 42 photoproduction. a 40, 41. 97. 98. 148. 149,

205, 206 from alkaline solutions by Pt-Fe,O,. a 40 from Ptlp-lnP cathodes, a 205 with colloidal Pt-PVlt. a I49 by Pt-loaded alkaline aqueous TiO,. a 40 from H 2 0 with T present by PtITiO,, a 98

adsorption, in fuel cell electrodes, a on Pt, Pd, Rh on Cr,O,. a

in Pd foil. electrochemistry. a

by Pt/,Rh/SrTiO, powders. a 206 with Pt colloids/polymerised micelles,

simultaneous with CO, reduction. a I49

using Ru(bpy):+, a 206

with Pt/CdS. a I48 using CdSIRh, CdS/Pt. a 41 from RuO,/CdS, a 41 from aqueous sulphide solutions by

polypyrrole/RuO, . u I49 from HIS. a 98, 149, 206

from Pt/thylakoid, a 97

Hydrogen (contd.) Page plasma, ions detector. a 207 production, [PtH(PEt,),l+, from water, a 205

of methyl formate, a 100 reaction with Rh(acac)[P(OPh),l,. a 151

I5 I , 208, 209 151

Hydrogen Sulphide, photodecomposition to H I . a 98, 149. 206

Hydrogenation, alkenes, alkadienes, a 208 alkenes, alkynes, a 45 alkyne to alkenes, a 100 benzene, n 209 CO, C,H,. benzene, toluene 23 CO, over Pd, a 43

over Ir, a 100. 208 over Rh, a 151, 208, 209 over Ru-Rh, a 45 over Ru, a 44 CO, on Ru/C black, a 151

C,H,, a 44 4-methylcyclohexanone. a 44 olefins, a 44. 208 pent- 1 -ene, a 44 polyunsaturated hydrocarbons. a I50 soybean oil, a 43

Hysteresis, in Ti/WO,/lr, a 100

with CO, a with CO, CO, , a

63, Impressed Current System Institution of Mining and Metallurgy, Annu.

International Precious Metals Institute, annual

Iridium, crucibles, for crystal growing electrical resistivity, a industrial uses IV’lr analyser for UO,/PuO,. a Ir MOS, NH, biosensor, a medical uses superlattice with Rh, a Ti/WO,llr, IIV characteristics. a

Iridium Oxides, thin films, preparation,

Commodity meeting

conference

properties. a Isomerisation, over platinum metals. a 44.

158

166

196 12 38 12 99 99 I2 39

100

204 209

Jewellery, platinum alloys I95 Johnson Matthey, ammonia oxidation test rig 168

at Techmart exhibition 167 university loans scheme 167

99 Pt, Pt alloys to Cu. Ni alloys I32 reaction bonding metals to ceramics I29

41, 152

Joining, Pt to Ti, a

Ketones, production from alcohols. a Kilogram, international standard 74

Laboratory Apparatus, a 42. 98. 99. 150. 207 Langmuir-Blodgett Films, a 147, 152 Lead, automotive emissions. control I06

tolerant catalysts, a 208 Light, international standard, history of 84

reflection by Pt, Rh. Os, Au. a 96

Magnesium, promoter for Pt/Ti02, a 98 Magnetism, PtCo, permanent magnetic films. a 38

Fe,Pt, shape memory effect. a 38 PtMnSb thin films, a 204 UPt,. a 38

Magnetohydrodynamics, generators 2 Mass, international standard 74 Medical, biomedical engineering 13

“Paraplatin”, anti-cancer drug 116 204

ultrapure drug production 69

splitting, u 207

Pt(I1) complexes, water soluble, a

Membranes, Pd/Cu on Ta. Nb in water


Memory, shape. in Fe,Pt. u Memory Device, optical photochemical, a Metals, reaction bonded to ceramics Methane, reactions. a

synthesis. a Methylcyclohexane, H , energy system

H, production, for engines. u 4-Methylcyclohexanone, hydrogenation. u Methyl Formate, production, u Methyl Methacrylate, photopolymerisation Molecular Beam Epitaxy, Pt interaction u

Molybdenum, activated sintering Moscow International Exhibition

GaAs, u

Puge 38 98

42. 99

Palladium Alloys, amorphous, in NaCI. ( I

I29 Palladium-Cerium, ingot. structure. u Palladium-Gold, phase diagram, u

I74 Palladium-Iridium-Phosphorus, for CI 43 evolution from NaCI. a 44 Palladium-Nickel, coatings. new HCI

100 electrolyte, a I. (1 206 high speed plating, u (ith

PdNiSi. wires. structural behaviour. ( I

100. 151 Palladium-Hydrogen, electrochemistry. ( I

Palladium Complexes, AcOPdO, . superoxo.

Palladium Hydride, sensor, for H detection. (I

Palladium Silicide, Pd2Si. formation in

98 oxidation agent. u 184 130

Dresence of H. a

Nitric Acid, manufacture, test rig for I68 100

Nitrobenzenes, reduction to anilines. u 209 Nitrogen, detection in amino acids. u 207 Nitrogen Oxides, emission control. U.S. experience 106

NO, adsorptions. a 39. 147 43

reductions, u 99. 151 207

glass. (1 96

Pt, Rh recovery from, a

reactions with CO. 0,. a

NMR, '"'Pt spectroscopy. variable temperature, u Nuclear Waste, Ru in borosilicate metals for

Olefins, reactions over platinum metals. u 44. 151 152. 208

Optical Memory Device, a 98 Optical Properties, Pt 20, 21, 38. 41 Organic Compounds, (Ph,P),C = CH,

addition to. u 209 Organometallic Chemistry, Pd, book review I83 Organometallic Compounds, dictionary.

book review 72 Osmium, reflection of light. a 96 Osmium Complexes, [(bpy),(OH,)Os"'OOs'V(OH)(bpy),]' +. u I47

Oxidation, alcohols, u 42. 150, 152 alkenes. u 96 CO. CH,. C ,H , . H,. u 42 co. (1 43. 150, 208 glucose oxidase. u 205 photo, bromide ions, a 206

cyanide wastes I I . 40 platinum jewellery alloys I95

I47 chemisorption on 0 s clusterlsupport 14 detector. literature review, u 207 evolution, at platinised TiO, electrode. u 40

at Pt/Bi,RulO, electrode, u I48

photoproduction, u 40. 41. 97. 149. 206 reactions. u 41. 96 storage in exhaust catalyst. u I50

[Os(CNR),](PF,), . synthesis. u 39

Oxygen, adsorption on Pt(210). a

for H,O production, u 43

Pacemaker Leads Palladium, anodic dissolution in chloride solutions

clusters. H , chemisorption. diffusion on, u coated membrane, for H ,O splitting. u composites. Pd-Cu, in contacts

compounds. ZrU,,Pdu.,, as temperature reference, u

electrical resistivity, a film on Si MIS, H, detection, u organometallic chemistry. book review PdNiP glass melts, He solubility in . u Pd MOS, H detectors, u PdO-Pd MOSFET CO sensor, u plating. electroless. u

process. high speed. u thin films. electrical resistivity, a

42.

"Paraplatin", new anti-cancer drug Permeability, control by Pt grid. a Petroleum, refining, catalysts. conference pH, sensing by Pd electrodes. u Phase Changes, Pd Ce. a

Fe,Pt. u IJPt,. u - - - > . -

Phase Diagrams, Pd-Au, 61 Pd-Nd-U. u PI-AI. u Pt-2-Y at IO00"C

Photocatalysis, u

Photochemical Smog Photodiodes, AulPtiTi metallisations in. u Photography, platinum prints of Emerson Photo-Oxygenation, alkylbenzenes. (1

Plating, Pd. u 41. Pd-Ni. u 42. Ru. a

40, 41, 97. 98, 149, 205.

Platinotype, Emerson's photographs "Platinum 1986" Platinum, annual commodity meeting

batteries. for Greenwich time signal. history biosensor. NH,. PtMOS. u black. coatings, reflectance black powder. as heat exchanger. u bonding to Ti, d i d phase, u claddings. on base materials coatings, cermet. Pt-AI ,O ,, u compounds, blues, review. u

cluster. review, u Pt(IlI), properties, preparation. u PtMnSb thin films. magneto-optical

properties. u corrosion protection for reinforced concrete drug. "Paraplatin" evaporation. for molecular beam epitaxy. (I

gauze for Ag separation from Cu, u gratings, structure, u grid for permeability control. u ignition, in hydrogen engine. u layers in InPtlGaAs electrical contacts. u metallisation in Ge-APD. u pacemaker leads

13 '"Pt NMR spectroscopy. u 80 reflection of light. u

I47 standard of light 207 transparent films 67 urea-paint/Pt gate MOSFET for ovcrhcating

detection. u 2 10 wire. ultrafine. fabrication 38 for HCN synthesis, u

207 I83 for jewellery, oxidation behaviour 204 pacemaker leads 207 Platinum-Aluminium, diagram. u 42 Platinum-Cobalt, sputtered. magnetic films.

I49 Platinum-Iridium, mass standard 41 Fe,Pt, shape memory effect, u

204 Platinum-Oxygen, films. optical properties.

Platinum Alloys, claddings. on base materials

Pug4 205 96 38 38 97

I48

42 I 5 0

96 207

38 I16 39

I96 97 ,. 38 38 38 38

I47 I47 79

148. 206 1 1 1 152 I82 206 I49 I50 42

I82 I46 I66 29 99 21

I50 99

I32 41 39 96 39

204 158 I I6 98

152 I52 39 -.

I52 46

I52 13

207 96 84 20

207 27 99

I32 I95

13 I47

, (1 38 74 38

u 38


Page Platinum-Palladium-Rhodium,-Ruthenium,

gauzes, a 96 Platinum-Rhodium, catalytic reconstruction 54

recovery from HNO, acid manufacture. a 100 U R , , magnetic, superconducting properties, a 38 Platinum-Zirconium, Sn, Ru doped. fuel cell

electrodes, a 2 10 Platinum-Zirconium-Yttrium, phase diagram 79

Platinum Complexes, cis-Pt(II), water soluble, a 204 [PtH(PEt,) , I +, electrochemistry, H,

production. a 205 [ Ni ,,Pt,(CO),, H6.,,ln-. clusters, synthesis, a 39

42 gate electrodes, a 46 glass transition. a I47 Schottky barriers in IR-CCD, a 46

I84 chemistry, conference announcement I19 co-ordination compounds, history I98

Platinum Silicide, formation from Pt and SiH, , a

Platinum Metals, additives in activated sintering

Platinum Metals Alloys, Ta-, Ti-,

Plutonium, concentration, by ly2Ir analyser. a 99 Poisoning, catalytic converters. a 42 Pollution Control, automotive exhaust. a 43. 150

automotive three-way catalyst. a 99. 106, 208 cyanide wastes I I , 40

Polymerisation, photo-. styrene. divinylbenzene. a 206 Powder Metallurgy, sintering. activated I84 Powders, Pt/TiO, /Nation, Br- oxidation. a 206 Printing Head, barium ruthenate 1 40

Propane, reactions, a 150, 208 Proteins, cyclic voltammetry of, u 40

I so Reaction Bonding, ceramics-metals I29 Rebars, in concrete. corrosion protection I58 Reduction, hydrocarbonate anions, a 205 Refining, petroleum, catalysts, conf. rep. I96 Reforming, C , hydrocarbons. a 208 Resistance Thermometers, a 46. 210 Review, Int. Symp. Biomedical Engineering 13

literature, of water photodecomposition. a 206 0 detectors. a 207 Pt cluster compounds, a 96 Pt(II1) compounds. preparation. properties, a 39 progress in anodic detection in flowing

solutions. a 207 Rhenium, activated sintering I84

204 Rh,oAI,,.,Cu,. crystal growth. a 205

electrical resistivity, a 38 reflection of light, a 96 single crystals. NO adsorption. desorption. a 39

ohotochemical behaviour. a 98

electrocatalytic properties 121

U.S. experience 106

Propan-2-01. dehydrogenation. a 97

Proton Injection, from Pd electrode, a

Rhodium, compounds, Rh,As. synthesis. a

Ruthenium, compounds, RuS,. catalytic.

Ru(CN):-/Ru/CN) A ~, Ru(NH , ) I py ' + , electrochemistry of. a

electrodeposition from LiCI-KCI melt, a in glass for nuclear waste, a on CdTe. amphoteric behaviour. a superlattice with Ir. a

[Ru(bpy),]'+. [RuC, 2B]' +.'luminescence. u Ru(2,3-bis(2-pyridyl)pyrazine). a [Ru(CNR),](PF,), synthesis. a Nd,.,Cu Ru O,.,, a

Ruthenium Complexes, on SnO,. electrode. a

Ruthenium bxide, RuO, thick film. I/f noise. a

Schottky Barriers, PtSi in i.r.-CCD. a Seawater, desalination. a Shape Memory, in Fe,F?. a Silica, colloidal, removal from seawater. a Silver, separation from Cu, hy Pt gauze, a

205 42 96 96 39 97 39

I47 39

I48 204

46 40 38 40

152

Page Sintering, activated I84

Solar Cells, Ptln-Si electrode, a 205 Soybean Oil, a 43. 151 Spectroscopy, '"Pt NMR. variable temperature, a 207

light 84 Stereodynamics, I y 5 Pt NMR spectroscopy for, a 207 Structure, Pd-Ce, a 38

Pd-Au, a 38 Ni-Pt clusters. a 39 Ru-Ir, superlattice, a 39

Styrene, reactions, a 152, 206 Sulphur, detection in flowing solutions, a 207

in wear tracts in Pd, a 210 photoproduction from sulphide solutions. a 149. 206

Superconductivity, UPt, . a 38 Syngas, reactions, a 43. 44. 45. 100, I5 I , 208. 209

Techmart, Barclays, technology transfer exhibition 167 Technology, platinum. Moscow Exhibition 130

platinum, Techmart Exhibition 167

Temperature Measurement, a 46. 210 Temperature Scale, IPTS. revision proposals, a 46 Thermocouples, Rh + 0.5 Fe-chromel. in high

S.I. Units, international kilogram 74

Standard, international kilogram 74

Tantalum Alloys, electrocatalysts I20

Temperature Control, 85-IOSK. a 210

pressure cells, a 210 Thick Films, Ru0,-based. IIf noise, a Thin Films, IrO,, preparation, properties. (I

204 204 100

Pt, structure, a I52 PI-Co, permanent magnetic. a 38

Pt/mica electrodes, a 148 Pt on p-lnP, photocathodes. a 205 resistor. barium ruthenate. printing head I40

Thiocyanate, formation from C N ~ using RhiCdS. a 206

Toluene, hydrogenation 23 in H energy system I74

Tritium, effect in H ? photoevolution. a 98 oxidation over Pd/-. Pt/AI,O,. a 42

Tungsten, activated sintering I84

University Loans Scheme, operated by

TilWO ,/Ir. I/V characteristics. a Pd. electrical resistivity. a 204

PtMnSb, magneto-optical properties, a 204

Titanium Alloys, electrocatalysts I20

Johnson Matthey I67 99

68 205 I20

of redox proteins, a 40 for fuel cell electrodes, a 209

39

40. 41. 97. 98. 149. 206

photodecomposition. literature review, a 206

43 207 42

Water Gas Shin Reaction, a 44,45 Wear, on Pd alloy/Au alloy surfaces. a 210 Wire, Pd, Rh. Ir . W, electrical resistivity. a 38

Ir-based Ti. for corrosion prevention I58 PdNiSi amorphous. mechanical properties. a 96

99 Pt. ultrafine, fabrication 27 Pt-clad Cu-cored Nb. for corrosion prevention 158

27

Uranium, concentration. by "'lr analyser, (1

Vitamin K , , ultra pure. production Voltammetry, cyclic. of [PtH(PEt,),]+. u

of Ta. Ti-platinum metal alloys

square wave. Pt microdisk electrode. a

Water, photochemical splitting. a

photoreduction with CO:. a 206 production on Pd-SO,-Si from O'-H?. a thermochemical splitting. laboratory cycle. a tritiated. adsorption in catalyst bed. a

Pt. for HCN synthesis. a

Wollaston, W.H., fine wire production method

Young's Modulus, amorphous PdNiSi wires. a 96


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