Developments in direct thermochemical liquefaction of biomass: 1983-1990

Energy & Fuels 1991,5, 399-410 399

Reviews

Developments in Direct Thermochemical Liquefaction of Biomass: 1983-1990

D. C. Elliott* Battelle, Pacific Northwest Laboratories, Box 999, Richland, Washington 99352

D. Beckman Zeton Inc., Burlington, Ontario, Canada

A. V. Bridgwater Aston University, Birmingham, United Kingdom

J. P. Diebold Solar Energy Research Institute, Golden, Colorado

S . B. Gevert Chalmers University of Technology, Goteborg, Sweden

Y. Solantausta Technical Research Centre of Finland, Espoo, Finland

Received October 11, 1990. Revised Manuscript Received January 17, 1991

This review catalogs the process research in direct thermochemical conversion of biomass to liquid hydrocarbon fuels. Subject areas include pyrolysis, high-pressure liquefaction, upgrading of both pyrolysates and high-pressure oils, supporting analytical and basic research, and technoeconomic assessments. Much progress is presented for the time period from 1983 to 1990. The pyrolytic processes with lower investment costs and higher yields of more oxygenated oils are moving more quickly forward in development. Further development is still required for the upgrading processes for the production of hydrocarbons from the primary oils. Based on these developments, potential exists for economical production of substitute liquid hydrocarbon fuels and chemicals from biomass.

Introduction This paper summarizes the developmenta in the state

of the art of direct liquefaction of biomass from 1983 to 1990. This review is the joint effort from the Working Group of the International Energy Agency (IEA), Bioen- ergy activity on direct liquefaction of biomass. The members of the working group are a team of researchers representing Canada, the European Community, Finland, Italy, Sweden, the United Kingdom, and the United Statea. The information presented in this paper is primarily derived from the research programs which were or are now under way in the participating countries.

The IEA activity on direct liquefaction of biomass has evolved in several stages. The objectives of the activity include

1. identifying potential improvementa to developing process concepts;

2. evaluating technically and economically the developing processes in direct thermal liquefaction; and

3. promoting information exchange among the participating countries.

0887-0624/91/2505-0399$02.50/0

The initial work of the IEA Working Group, which was completed in 1984 under the title of Biomass Liquefaction Test Facility (BLTF), included in its final report a volume describing the state of the art at that time.' The second stage of the activity, operating from 1986 to 1988 under the name Direct Biomass Liquefaction (DBL), continued the information exchange among the participants begun in BLTF, but an updated state of the art was not published as part of the final report? Now, in the third stage of the activity, Assessment of Liquefaction and Pyrolysis Systems (ALPS), the expanded group of members has updated the earlier state-of-the-are review based on the significant progress made worldwide in this field in the 1980s.

(1) Beckman, D.; Bergh, A.; Elliott, D. C.; Kannel, A. IEA Co-Opera- tiue Project D l , Biomass Liquefaction Test Facility Project, Volume 2: State-of-the-Art Reuiew. National Technical Information Service: Springfield, VA, 1988, DOE NBM-1062 Vol. 2.

(2) Beckman, D.; Elliott, k. C.; Gevert, B.; Hbmell, C.; KjebWm, B.;

ment of Selected Biomass Liquefaction Processee. Final Report of IEA Cooperatiue Project Direct Biomass Liquefaction; Technical hearch Centre of Finland: Espoo, Finland, ISSO, Report 697.

batman, A,; Solantauta, Y.; "'Ulenheimo, v . Techno-Economic A8Se88-

0 1991 American Chemical Society

400 Energy & Fuels, Vol. 5, No. 3, 1991

This review is limited to thermal processes that maximize liquid products. By this definition we specifically omit fermentation fuels, char slurries, or indirect liquefaction products, such as methanol from synthesis gas or Fisher-Tropsch liquids. The research efforts are cate- gorized according to the two main types of direct liquefaction, pyrolysis and high-pressure liquefaction; biomass liquids upgrading; other biomass liquefaction research; and technoeconomic assessments.

Pyrolysis Pyrolysis processes intended to maximize liquid yields

are presented here. Much of this work is ongoing, and earlier developments from many of the research groups were described in the original state-of-the-art review.'

Entrained-Flow Pyrolysis: Georgia Tech Research Institute, Atlanta, GA. In this system, powdered wood (0.30-0.42 mm) was entrained in a straight tube by a flow of stoichiometrically combusted flue gases. The heat for pyrolysis was supplied by these carrier gases. If the carrier gases were too hot, significant losses from the first-formed vapors took place to result in higher overall gas yields. Consequently, fairly large amounts of tempered carrier gases at 745 "C were used at a carrier-gas-to-biomass weight ratio of about 8 to supply the heat of pyrolysis to maximize the yield of oil.

The diameter of the entrained-flow reactor was 15 cm and the length was 4.4 m, which resulted in a residence time of 1-2 s. This residence time was a compromise between the length of time needed to pyrolyze the size of particles fed on a once-through basis and the need to minimize the time that the pyrolysis vapors spent in the reactor. Feeding rates were typically about 15 kg/h and resulted in yields of 58% organic condensates (moisture- free basis) and 12% char (maf feed) with a total mass closure of 101% (including the large amount of carrier gases). The pyrolysate was recovered along with the water formed in the combustion used to directly heat the carrier gases, as well as any water formed during pyrolysis, or which was present as moisture in the feed, resulting in condensates containing about half water.a4

Vacuum Pyrolysis: Universit6 Laval, Sainte-Foy, Quebec, Canada. Biomass was pyrolyzed under vacuum in a staged multiple hearth furnace at typical temperatures of 350-450 "C. Liquid product fractions were collected from each stage of the furnace. Feeds studied included wood chips, bark, agricultural residues, peat, and municipal solid wastes. Investigations of energy products, liquid fuels and charcoal, and chemical products were undertaken. These studies were conducted in a 20-35 kg/h process development unit." Work was also undertaken on the characterization of vaccum pyrolysis products and on the separation of fine chemicals from the liquid product fractions using column chromatography.g11

Reviews

(3) Kovac, R. J.; Gorton, C. W.; ONeil, D. J. Thermochemical Con- version Program Annual Meeting; Solar Energy Research Institute: Golden, CO, 1988, SERI/CP-231-3356; pp 5-20.

(4) Kovac, R. J.; Gorton, C. W.; ONeil, D. J.; Newman, C. J. Pro- ceedings of the 1987 Biomass Thermochemical Conversion Contractors' Review Meeting; National Technical Information Service: Springfield,

(5) Roy, C.; de C a y i a , B.; Yang, J.; Plfurta, P. In Proceeding8 of the Seventh Canadran Bioenergy R&D Seminar, Hogan, E., Ed.; Energy, Mines, and Resources Ministry: Ottawa, Canada, 1989; pp 675-680.

(6) Roy, C.; w a u m i a ! B.; Pakdel, H. In Research in Thermochemical Biomass Conversion; Bridgwater, A. V., Kueeter, J. L., Eds.; Elsevier Applied Science: New York, 1988, pp 585-596.

(7) Roy, C.; Lemieux, R.; M a u m i a , B.; Blanchetta, D. In Pyrolysis Oib from Biomaur: Producing, Analyzing, and Upgrading; Soltea, E. J., Milne, T. A,, Eds.; ACS Symposium Seriee No. 378; American Chemical Society: Washington, DC, 1988; pp 16-30.

VA, 1987; CONF-8705212; pp 23-40.

Fast Pyrolysis: University of Waterloo, Waterloo, Ontario, Canada. Researchers developed the Waterloo Fast Pyrolysis Process, which involved rapid pyrolysis of biomass in a fluidized sand bed reactor at atmospheric pressure and temperatures typically from 450 to 500 "C. Extensive study of the process has been undertaken in two reactors, a 15-100 g/h bench-scale unit and a 2-3 kg/h pilot-scale unit. Feedstocks included wood, peat, and agricultural residues.12-14

Recent research included the following related areas: 1. Pretreatment of wood followed by pyrolysis for the

production of sugars from the cellulose fraction.16J6 2. Recovery of chemicals from the primary liquid

products. 17-19 3. Effect of the use of catalysts in the pyrolysis reaction

which promoted gas production.m From this research and Ensyn work described below, an

important paper describing the role of temperature in fast pyrolysis was published.21 It proposed that if the biomass particle heat-up time to 500 "C, for any reactor, is significantly less than particle residence time, then the temperature of the reactor will be the only variable determining the yields of char, oil, and gases for a given feed and given gas residence time.

Rapid Thermal Pyrolysis: Ensyn Engineering As- sociates, Gloucester, Ontario, Canada. The Ensyn process, referred to as Rapid Thermal Processing, used a heat-carrying solid particulate to contact the biomass, giving high heating rates exceeding 10000 "C/s in a specially designed thermal mixer. The feed and solid heat carrier then passed through a tubular transport reactor in which the pyrolysis reactions experienced a controlled residence time at temperature. Pyrolysis temperatures ranged from 400 to lo00 "C. Feeds studied include various types of biomass and biomass fractions such as l i i n and cellulose. Recent research was carried out in a 100 kg/h pilot

(8) Roy, C.; Pakdel, H. In Proceedings of the Seventh Canadian Bioenergy R&D Seminar; Hogan, E., Ed.; Energy, Minea, and Reaourcea Ministry: Ottawa, Canada, 1989; pp 681-686.

(9) Pakdel, H.; Roy, C.; Zeidean, K. In Research in Thermochemical Biomass Conversion; Bridgwater, A. V., Kueeter, J. L., Ede.; Elsevier Applied Science: New York, 1988; pp 572-584.

(10) Pakdel, H.; Roy, C. Biomass 1987,13, 155-171. (11) Pakdel, H.; Roy, C. In Pyrolysis Oils from Biomass: Producing,

Analyzing, and Upgrading; Soltee, E. J., Milne, T. A., Ede.; ACS Sym- poeium Series No. 376; American Chemical Society: Washington, DC, 1988; pp 203-219.

(12) Scott, D. S.; Piskorz, J.; Radlein, D.; Majereki, P.; Czemik, S. In Proceedings of the Seventh Canadian Bioenergy R&D Seminar, Hogan, E., Ed.; Energy, Minea, and Resources Ministry: Ottawa, Canada, 1989; DD 699-704. .. - ~ -

(13) Scott, D. S.; Piskorz, J.; Radlein, D. Ind. Eng. Chem., Process Des.

(14) Piskon, J.; Majereki, P.; Scott, D. S. Can. J. Chem. EM. 1990, Dev. 1986,24,581-88.

68, 465-472. (15) Scott, D. S.; Piskorz, J.; Radlein, D.; Czernik, S. In Proceedings

of the Seuenth Canadian Bioenergy R&D Seminar; Hogan, E., Ed.; Energy, Mines, and Resources Ministry: Ottawa, Canada, 1989; pp

(16) Piekorz, J.; Radlein, D.; Scott, D. S.; Czemik, S. In Reseorch in Thermochemical Biomass Conversion; Bridgwater, A. V., Kueatar, J. L., Eds.; Elsevier Applied Science: New York, 1988; pp 557-571.

(17) Radlein, D.; Grinshpun, A.; Piskon, J.; Scott, D. S. J. AM^. Appl. Pyrolysis 1987, 12, 39-49.

(18) W e i n , D.; Piskorz, J.; Scott, D. S. J. Anal. Appl. &rolysis 1987,

(19) Piskorz, J.; Scott, D. S.; Radlein, D. In Pyrolysis Oib from Biomass: Producing, Analyzing, and Upgrading; Soltea, E. J., M h e , T. A., Eds.; ACS Symposium Series No. 376; American Chemical Society: Washington, DC, 1988, pp 167-178.

(20) Garg, M.; Scott, D. S.; Piakon, J.; Radlein, D. In Sixth Canadian Bioenergy R&D Seminar; Granger, C., Ed.; BC Research: Richmond, B.C., Canada, 1988, pp 476-480.

(21) Scott, D. S.; Plekon, J.; Bergougnou, M. A.; Graham, R.; Overend, R. P. Ind. Eng. Chem. Res. 1988,27,8-15.

713-720.

12, 51-59.

Reviews Energy & Fuels, Vol. 5, No. 3, 1991 401

Vortex Ablative Pyrolysis: Solar Energy Research Instituta (SERI), Golden, CO. SERI developed the vortex reactor specifically for the fast pyrolysis of biomass. The feed particles were forced to slide on the hot cylindrical wall in a helical path through the reactor. The sliding contact of the particles on the wall resulted in very high heat transfer to the particle so that ablative pyrolysis was thought to take place. Partially pyrolyzed particles exited the reactor tangentially, mixed with fresh feed, and were recycled back to the carrier gas ejector. The recycle loop decoupled the residence times of the solids and the vapors, which allowed the vortex reactor to be insensitive to the particle size of the feed. The small amount of char that formed was recycled until it was attrited to a fine powder (-50 rm).% The typical 2-mm-thick feed particle made about 30 passes during a total residence time of 1-2 s through the reactor before it was completely pyrolyzed. Operation was typically at 13-20 kg/h of dry sawdust (-3 mm) with a carrier-gas-to-biomass weight ratio of 1-1.5. Yields on a dry feed basis have been 67% condensates (55% moisture-free organic liquids), 13% char, 14% net pyrolysis gases, and 12% water of pyrolysis for a mass closure of 94% of the feed (a 98% mass closure, if the nitrogen carrier gas is included in the calculation^).^^ Interchem has announced the completion of construction of a vortex reactor for a designed throughput of 1350 kg/h of dry wood.26

Ongoing studies indicate that a phenolic-rich extract can easily be prepared from the pyrolysis condensates made from sawdust, which can be used to replace at least 50% of the phenol in a phenol-formaldehyde resin at economically attractive costs.% An industrial consortium has been formed to commercialize this technology.

In related work, the reactor was modified to allow it to pyrolyze refuse-derived fuel (RDF), which contains tramp metals and other inert solids. Preliminary operation with RDF indicated that the plastic-derived condensates in- teracted with the lignocellulosic-derived condensates to form an asphalt-appearing material.27i28

Pyrolysis Mill: Colorado School of Mines (CSM), Golden, CO. The CSM reactor used two specially grooved disks, 6.4 cm diameter, made of copper, which were stacked one on top of the other. The biomass or RDF was centrally fed between the heated disks. As the bottom disk was rotated at 4-80 rpm, the feed particles made their way to the circumference of the disks in a spiral path and were allowed to fall to a cooler zone. The vapors and gases also exited a t the circumference of the disks. Maximum reported liquid yields from sawdust were 54% (including moisture) at disk temperatures of 600 OC, a flow of nitrogen

(22) Graham, R.; Freel, B. A,; Overend, R. P. In Proceedings of the Seventh Canadian Bioenergy R&D Seminor; Hogan, E., Ed.; Energy, Minee, and Resources Ministry: Ottawa, Canada, 1989; pp 669-674.

(23) Graham, R. G.; Freel, B. A.; Bergougnou, M. A. In Research in Thermochemical Biomass Conversion; Bridgwater, A. V., Kueeter, J. L., Eds.; Elsevier Applied Science: New York, 1988; pp 629-641.

(24) Diebold, J. P.; Scahill, J. W. In Pyrolysis Oils from Biomass: Producing, Analyzing, and Upgrading; Soltes, E. J., Milne, T. A., Eds.; ACS Symposium Series No. 376; American Chemical Society: Waah- ington, DC, 1988; pp 31-40.

(25) Diebold, J. P.; Power, A. J. In Research in Thermochemical Biomass Conversion; Bridgwater, A. V., Kuester, J. L., Eds.; Elsevier Applied Science: New York, pp 609-628.

(26) Johnson, D. In Roceedrngs of the R&D Contractors Meeting on Biomuss Liquefaction; Hogan, E., Ed.; Energy, Mines, and Resources -. Ministry: Ottawa, Canada, in press.

(27) Scahill, J. W.; Diebold, J. P. Thermochemical Conversion Pro- gram Annual Meeting; Solar Energy Research Institute: Golden, CO, 1988; SERIfCP-231-3355; pp 237-2146.

(28) piebold, J. P.; Evam, R. J.; ScahiU, J. W. In Energy from Biomass and Solrd Wastes XIXk Klaes, D. L., Ed.; Institute of Gaa Technolow: -- Chicago, 1990; pp 851-878.

purge gas of 0.5 g of N2 per gram of sawdust, and a feeding rate of 13 n/h.29J"

Fluid-Bid Pyrolysis: Technical Research Centre of Finland (VTT), Espoo, Finland. Flash pyrolysis of wood, bark, and peat was studied in a small continuous (100 g/h) fluid bed unit during 1986 and 1987.s11s2 This work was a collaboration between the University of Waterloo and VTT.

Material balances for the unit were produced, and products were characterized.% The organic liquid products were separated and identified by gas chromatography-mass spectrometry and characterized by infrared spectrophotometry and gel permeation chromatography.

The maximum yield of organic liquid products obtained from pine bark was about 50 wt % and that obtained from peat was about 40 wt % . The liquid products contained, at low temperatures below 600 "C, significant amounts of high-molecular-weight substances.

Pyrolysis for Liquids with Partial Combustion: Alten-Alternative Energy Technologies (a Consor- tium of KTI and Italenergie), Raiano, Italy. The pyrolysis plant, developed by Alten, has been in operation from 1985, and was the largest biomass pyrolysis unit (500 kg/h) dedicated to liquid fuel production in Europe. Feed was screened, rechipped, and dried in a rotary drier before entering the reactor. Feedstocks tested included wood chips, olive husks, straw, and vine trimmings. Air was added to the reactor to give a partial combustion reaction to provide reaction heat. The reactor operated at about 500 "C and 1 atm. Char byproduct was recovered in a hot gas cyclone; vapor and gas streams passed through a quench vessel where they were cooled and condensed by direct contact with recycle product water. The mixture of oil and water was separated in a gravity separator. Excess water was removed from the recycle stream with a chemical oxygen demand of 150 000 ppm.

The yield of raw oil was 20-25 wt % with a similar yield of charcoal. The raw oil was black and fairly viscous (55 CP at 70 OC). It contained around 31 wt % oxygen, 15 wt % water, and 10 wt % char in suspension. The density of the raw oil was 1.195 g/mL.M-37

Low-Temperature Pyrolysis for Liquids and Charcoal: Tubingen University, Tubingen, West Germany. The operating principle was to use low temperature (1350 "C) and long reaction times (160 min) to give low oxygen content oils.Mi38 The principle was li-

(29) Reed, T. B. Thermochemical Conversion Program Annual Meeting; Solar Energy Research Institute: Golden, CO, 1988, SERI/

(30) Reed, T. B. In Research in Thermochemical Biomass Conversion; Bridgwater, A. V., Kuester, J. L., Eds.; Elsevier Applied Science: New York, 1988; pp 192-202.

(31) Scott, D. S.; Piskorz, J.; Westerberg, I.; McKeough, P. Fuel Pro- cess. Technol. 1988,18, 81-95.

(32) Arpiainen, V.; Lappi, M.; Nissilii, M. Flash-Pyrolysis of Peat, Wood, Bark and Lignin. Part 3. Tests with Peat and Pine Bark; Technical Research Centre: Espoo, Finland, 1989.

(33) Arpiainen, V.; Lappi, M. J. Anal. Appl. Pyrolysis 1989, 16, 355-376.

(34) Bridgwater, A. V.; Graasi, G. Biomass Pyrolysis Liquids Up- grading and Utilisation; Elsevier Applied Science: London, in press.

(35) Antonelli, L. In Energy from Biomuss 4, Proceedings of the !Third Contractors' Meeting; Graeai, G., Pirrwitz, D., Zibetti, H., Eds.; Elsevier Applied Science: London, 1989; p 485.

(36) Antonelli, L. Energy from Biomass 4 , Proceedings of the Third Contractors' Meeting; Graeai, G., Pirrwitz, D., Zibetti, H., Eds.; Elsevier Applied Science: London, 1989; p 531.

(37) Antonelli, L. Improvement of Pyrolysis Conversion Technology Utilising Agricultural and Forestry Wastes; EEC Contract No. EN3B- 0121-1, interim and final reports; European Economic Community: Brussels, 1988, 1989.

(38) Bayer, E.; Kutubuddin, M. In Research in Thermochemical Biomass Conuersion; Bridgwater, A. V., Kuester, J. L., Me.; Elsevier Applied Science: New York, 1988; pp 192-202.

CP-231-3355; pp 247-258.


censed to several organizations in Europe, North America, and Australia, and several plants of up to 2 tons/h were operating or were under construction based on sewage sludge or municipal solid w a ~ t e . ~ ~ ~ ~

At a laboratory scale, both batch and continuous screw reactors were used with sewage sludge, MSW, wood, and agricultural waste. In the batch tests, dewatered sludge or other biomass was heated slowly to 300-350 "C in an oxygen-free environment for about 20 min, and the liquid product collected in an ice-cooled bath. The continuous unit was based on an indirectly heated auger kiln. No additives were needed as the silica, silicates, and heavy metals present in the sludge were claimed to act as catalysts. The vapor was condensed and collected. Oil yields ranging from 18 to 27 wt % and char yields from 50 to 60 wt % were achieved. The H:C atomic ratio was around 1.7 and the oxygen content about 15 wt 90 from biomass and below 5 wt % from sewage s l ~ d g e . ~ ~ * ~ l

Updraft Fixed-Bed Pyrolysis for Charcoal and Bio-Oil: BioAlternative S.A., Switzerland, Spain, and Italy. Feedstocks tested included wood, MSW, bark, sawdust, grape wastes, olive oil wastes, and coconut shells. The feed, in particle sizes ranging from 5 to 500 mm, was first crushed and dried (optimal moisture content 10% to 15%) before being transported to the top of the reactor from the feed hopper. A unit 3 m high and 1 m in diameter had a capacity of about 50 kg/h. It was fitted with an interlocked twin feed hopper fed by a screw feeder. A horizontal stirrer and a vibrator were used to prevent bridging of the feed in the reactor. The heat necessary for the reaction was obtained through internal combustion, regulated by a system of air injection tuyeres. The system was operated at slightly below atmospheric p re s s~re .~* 'S~

Product vapor left the top of the reactor at 120 "C and was contacted with hot pyrolysis oil to condense a single-phase product oil while keeping most of the water in the gas phase. The gas with about 10-20% water was blown to a boiler for cofiring with fuel oil, thereby incin- erating the wastewater.A3 The oil yield was 6 1 3 % and the char yield was 28-32%. The H:C atomic ratio of the oil was 1.46; the oxygen content was about 35 wt %; the viscosity varied from 250 CP a t 60 "C to 10 CP at 70 "C; and the density was 1.21 g/mL. The liquid product was successfully used as a boiler fuel.

High-pressure Liquefaction The focus of biomass liquefaction has shifted away from

high-pressure processes in the past 5 years. Research has shown that the fast pyrolysis oils, although of higher oxygen content, are less viscous and can be produced in greater yields at less cost. Since the high-pressure oil appears to no longer hold any significant advantage in the upgrading arena, the production cost of the primary oil appears to be decisive. Most of the research efforts described in this section are continuations of work cited in the earlier review.' Many of the original programs described in the earlier review are no longer active, and only a few new studies have begun.

Reviews

One attempt has been made at a unified treatment of the biomass liquefaction experimental data in the litera- turea4 That study concluded that the rate-determining step was dissolution of the solid substrate. Further, the processes could be readily separated into those based on hydrolytic cleavage in aqueous media followed by formation of oil product and those that primarily use pyrolysis to simultaneously solubilize and produce oil in nonaqueous media.

Extrusion-Fed Reactor System: University of Ar- izona, Tucson, AZ. The liquefaction of biomass in pressurized solvents was demonstrated at The U.S. De- partment of Energy's (DOE) Biomass Liquefaction Ex- perimental Facility, formerly at Albany, OR, in the late 1970s and early 1980s.' This process was operated at 21 MPa pressure, 20 min residence time, with a sodium carbonate catalyst at a throughput of 18 kg of wood/h. Research in this area was shifted to the University of Arizona in the early 1980s and has focused on improving the solids content of the slurry of biomass solids fed into the high-pressure reactor. Higher contents of biomass in the feed allow a smaller, more economical reactor vessel to be used for a given throughput.

Mixtures containing as much as 60% wood flour in product oil have been pumped into pressurized containers, using a modified extruder originally designed to extrude plastics. With this technique, early liquefaction experiments at the University of Arizona were conducted at 375-400 OC, 5.5-21 MPa pressure, on 40% wood flour in Albany oil with a residence time of between 1 and 4 h, and both with and without carbon monoxide and sodium carbonate catalyst. Recent exprimentation was directed toward the recycling of the product oil containing ap- proximately 40% fresh wood flour, along with water and carbon monoxide to result in a carrier oil composed primarily of material made at the University of Arizona. The fluid product distilled from the carrier oil had a heating value of 37 MJ/kg and a residual oxygen content of 7-10% Rough calculations of the oil yield showed that it was 80% to close to 100% of that theoretically attainable (48% to 58%, depending on assumptions)." The throughput of dry wood was 5-14 kg/h.

Peat Liquefaction: Royal Institute of Technology (KTH), Stockholm, Sweden. Liquefaction of peat at KTH was accomplished by two different methods. In the wet concept, the peat was not dried before liquefaction and the water could be decanted off after liquefaction. In the other method, the peat was dried and liquefied in a hydrogen donor solvent.

The wet process research especially addressed the effect of selection of raw materials. The calorific value and the oxygen content were better bases of selection of peat for liquefaction than the degree of humification. The conclusions concerning the peat raw material were general and could probably be used in systems other than liquefaction of wet peat.4g62

(39) Bridle, T. R.; Campbell, H. W.; Sachdev, A.; Marvan, 1. Thermal Convemion of Sewage Sludge to Liquid and Solid Fuels. Can. Soc. Chem. Eng. Conf., Toronto, Oct 1983 1983.

(40) Bridle, T. R. Enuiron. Technol. Lett. 1982, 3, 161. (41) Bayer, E. Proceedings of the Conference Verfahrenstechnik der

Klarschlammoerwertung; VDI: Baden-Baden, 1984; pp 141-156. (42) BioAltemative. In Proceedings of a Worhhop held in L'Aquila,

Italy; EUR 11382 EN; Mattucci, E., Graesi, G., Palz, W., Eds.; Com- mission of the European Communities: Brussels, 1989; p 206.

(43) Manufacturer's information: BioAlternative, S.A., Engollen, Neuchatel, Switzerland.

(44) Overend, R. P.; Chomet, E. In Research in Thermochemical Biomass Conuersion; Bridgwater, A. V., Kuester, J. L., Eds.; Elsevier Applied Science: New York, 1988; pp 411-428.

(46) White, D. H.; Wolf, D.; Zhao, Y. Prepr. Pap.-Am. Chem. SOC., Diu. Fuel Chem. 1987,32(2), 106-116. (46) White, D. H.; Wolf, D. Thermochemical Conuersion Program

Annual Meeting; Solar Energy Research Institute Golden, CO, 1988,

(47) White, D. H.; Wolf, D. In Research in Thermochemical Biomass Conuersion; Bridgwater, A. V., Kuester, J. L., Ede.; Elsevier Applied Science: New York, 1988; pp 827-842.

(48) BjBmbom, E.; Oleson, B.; Karleson, 0. Fuel 1986,65,1061-1066. (49) BjBrnbom, P.; Karleson, 0.; H6mell, C.; BjBmbom, E.; Pyamali,

SERI/CP-231-3355, pp 67-66.

M. Int. Peat J. 1987,2, 137-162.

Reviews Energy & Fuekr, Vol. 5, No. 3, 1991 403

achieved in less than 1 min. The physical processes which occurred at the macro scale were evaluated in particular by using a scanning electron microscope.m@ The pho- tographs obtained clearly showed the softening and flowing of the matrix at temperatures of 280 OC. Other activities included steam/water pyrolysis of cellulose and analysis of products for valuable chemical^.^^

High-Pressure Liquefaction: V", Espoo, Finland. High-pressure liquefaction of peat was studied experi- mentally from 1982 to 1986.88 Although the studied concept was assessed feasible, interest toward synfuel research in Finland was diminishing. The emphasis was shifted to conversion of black liquor, since the process concept studied offered considerable p ~ t e n t i a l . ~ ~

The peat liquefaction research that began at V" in the beginning of the decade was concluded with an experimental study of the hydroprocessing of peat tar in 1988-1989 together with the University of Toronto.70 High yields of liquid hydrocarbons were produced. The study confirmed one of the results of the DBL project, which concluded peat was the most economic feedstock alternative for biomass-based transportation fuel production. Peat has chemical properties that make it suitable for conversion to liquid products.

Presently the emphasis on direct liquefaction at VTT is focused on the conversion of black liq~or.7~" The yield of organic phase is around 40 wt % of black liquor organics. Production of fuel oil substitute at a pulp mill offers considerable promise in some cases. The primary liquid product has been successfully hydrotreated in batch teats.75 The aim of upgrading is to improve the quality of liquid product for a gas turbine fuel.

A major part of the black liquor research has been the analytical effort.7B*T7 Among others, methods to determine the degradation products of holocelluloses have been developed.

Cooperation on upgrading of black liquor and degraded lignin within the European Community JOULE program is planned.

Some research work on peat hydrotreatment was also conducted earlier at the University of Oulu, Finland.78

Liquefaction of dry peat has been carried out in a syn- thetic solvent containing tetralin, naphthalene, and p- cresol to evaluate the type of properties needed for a recycle solvent.63 As has been generally found, the hydrogen-donating properties of the solvent are more effective if the solvent contained hydroaromatic functionality. The dissolution of the peat was increased with the hydrogen- donating capacity of the solvent. The molecular distri- bution was increased with increased dissolution.

A method for analyzing the content of different functional groups has been developed based on infrared spectra, as were calibration curves on a large number of compounds with different functional groups." Related work dealt with analysis by gel permeation chromatogra- p h ~ . ~ ~

Liquefaction via Solvolysis: University of Sher- brooke, Sherbrooke, Quebec, Canada. Investigations of processes for the fractionation and liquefaction of biomass were undertaken. The importance of solvent type on these processes was identified.Mi57 Poplar or aspen wood and cellulose were treated in aqueous media at temperatures from 150 to 270 "C, using passage through a homogenizing valve to solubilize the c ~ m p o n e n t a . ~ ~ ~ ~ Further studies were reported with the woods in nonaqueous media, creosote, and ethylene glycol.soS1 With the homogenizing valve as a pretreatment means for prepa- ration of the feed slurry, oil yields of 4040% were obtained at 340 "C in 4-6 min at a feed rate of 4 kg/h (of dry wood) in a tubular reactor system.

More recent processes studied were (1) thermomechan- ical vapor-cracking, (2) continuous steam/aqueous fractionation, and (3) thermochemical solvolytic process. These studies were aimed at determining and optimizing the recoveries of the various biomass fractions. The feedstock tested was poplar wood (Populus deltoides)F2

Steam/Water Liquefaction: University of Toronto, Toronto, Ontario, Canada. Recent research at the University of Toronto involved the rapid steam/water pyrolysis of wood at sizes significantly larger than typical powdered feeds. In laboratory studies, poplar or willow wood, in the form of chips, sticks, and dowels up to 3 cm diameter, was pyrolyzed by steam injection at temperatures from 330 to 350 "C, in a 600-mL cylindrical batch r e a c t ~ r . ~ ~ , ~ Acetone-soluble oil yields of 40-50% were

(50) Bjambom, P.; Bjambom, E. Fuel 1987,66,779-784. (51) Bjbmbom, P.; Bjbmbom, E: Fuel 1988,67, 1589-1592. (52) BjBmbom, E.; BjBmbom, P.; K a r h n , 0. Fuel Process. Techno[.

(53) HBmell, C.; Bjambom, P. Fuel 1989,68,491-497. (54) Karlsson, 0. Fuel 1990,69,613-616. (56) Karlsson, 0. Fuel 1990,69,608-612. (56) Vanaeee, C.; Chornet, E.; Lemonnier, J. P.; Heitz, M.; Overend,

R. P. In Sixth Canadian Bioenergy R&D Seminar; Granger, C., Ed.; BC Research: Richmond, B.C., Canada, 1988; pp 457-462.

(57) Heitz, M.; Vincent, D.; Chomet, E.; Overend, R. P.; Sastre, H. In Research in Thermochemical Biomass Conversion; Bridgwater, A. V., Kuester, J. L., Eds.; Elsevier Applied Science: New York, 1988, pp 429-438.

(58) Heitz, M.; Carrasco, F.; Rubio, M.; Chauvette, G.; Chornet, E.; Jaulin, L.; Overend, R. P. Can. J. Chem. Eng. 1986,64,647-650.

(69) Abatzoglou, N.; Bouchard, J.; Chornet, E.; Overend, R. P. Can. J. Chem. Eng. 1986,64,781-786. (60) Vaneme, C.; Lemonnier, J. P.; Eugane, D.; Chomet, E.; Overend,

R. P. Can. J. Chem. Eng. 1988,66, 107-111. (61) Vaname, C.; Chomet, E.; Overend, R. P. Can. J. Chem. Eng. 1988,

66,112-120. (62) Bouchard, J.; Nguyen, T. S.; Chomet, E.; Overend, R. P. In Pro-

ceedings of the Seuenth Canadian Bioenergy R&LI Seminar; Hogan, E., Ed.; Energy, Mines, and Resources Ministry: Ottawa, Canada, 1989; pp 42-29.

(63) Boocock, D. G. B.; Chowdhury, A.; Koaiak, L. In Research in Thermochemical Biomcure Conversion; Bridgwater, A. V., Kueeter, J. L., Ede.; Elsevier Applied Science: New York, 1988; pp 843-853.

1988,17, 263-276.

(64) Boocock, D. G. B.; Chowdhury, A.; Koeiak, L.; Fruchtl, R. A. In Proceedings of the Beuenth Canadian Bioenergy R&D Seminar; Hogan, E., Ed.; Energy, Mines, and Resources Ministry: Ottawa, Canada, 1989; pp 693-698.

(65) Boocock, D. G. B.; Porretta, F. J. Wood Chem. Technol. 1986,6,

(66) Boocock, D. G. B.; Kosiak, L. Can. J. Chem. Eng. 1988, 66,

(67) Boocock, D. G. B.; Allen, S. G.; Chowdhury, A.; Fruchtl, R. In Pyrolysis Oils from Biomass: Producing, Analyzing, and Upgrading; Soltes, E. J., Milne, T. A., Eds.; ACS Symposium Series No. 376; Amer- ican Chemical Society: Washington, DC, 1988; pp 92-103.

(68) McKeough, P.; Tulenheimo, V. Techno-Economic Assessment of High-Pressure Peat Liquefaction; Technical Research Centre: Eepoo, Finland, 1987; Research Report No. 492.

(69) Technical and Economic Prospects for a Black Liquor Conuer- sion Process; Study for V l T by Jaakko P6yry Ltd., Helsinki, 1987.

(70) Oasmaa, A. "Upgrading of Peat Pyrolysis Oil". Internal report, Technical Research Centre: Espoo, Finland, 1989.

(71) Johaneson, A. Biomass 1984,4, 155-160. (72) McKeough, P.; Johanason, A. Pyrolysis Oils from Biomass:

Producing, Analyzing, and Upgrading; Soltes, E. J., Milne, T. A,, E&.; ACS Symposium Series No. 376; American Chemical Society: Wash- ington, DC, 1988; pp 104-112.

(73) McKeough, P.; A h , R.; Oasmaa, A,; Johaneeon, A. Roc. 4th Ew. Conf. Biomass, Orleans, Fr. May 11-15,1987 1987.

(74) A h , R.; McKeough, P.; Oasmaa, A.; Johansson, A. J. Wood Chem. Technol. 1989,9, 265-276.

(75) Elliott, D. C.; Oasmaa, A. Energy Fuels 1991,5, 102. (76) A h , R.; Oasmaa, A. Acta Chem. Scand. B 1988, 42, 563-666. (77) AlBn, R.; Oasmaa, A. Holzforschung 1988,43, 166-158. (78) Ala-aho, P. Turueteollisuw 1984,5, 62-67 (in Finnish).

127-144.

121-126.


High-pressure Liquefaction: Manoil/University of Manchester Institute of Science and Technology, Manchester, United Kingdom. Some early work was carried out with a ruthenium catalyst supported on alumina silicate in an aqueous medium, but recent work was carried out in tetralin or recycle oil with a nickel catalyst.7w1 Liquefaction of cellulose and organic constituents of dry municipal refuse, dried sewage, and straw was studied in the temperature range of 250-400 "C at about 10 MPa pressure and without additions of reducing gas. Oil yields were about 35 wt %.

Catalytic Hydroliquefaction: Institute of Wood Chemistry, Hamburg, Germany. A single-step process was investigated at the Federal Research Centre for For- estry and Forest Products in Hamburg. Catalytic hydroliquefaction in the liquid phase was conducted using a three 1-Lcapacity autoclave system, consisting of a reactor, hot separator, and cooler for simulation of a continuous process. Small biomass particles were mixed with recycle oil (starting oil was a mixture of pyrolysis oil with pitch tar from tall oil distillation) with catalysts.82-86

The most favorable results were obtained with palladium on active charcoal or iron catalysts.sB The conversion reaction was carried out at about 20 MPa of hydrogen at 380 "C for 15 min. Liquid products in the gas phase were flash-distilled in the hot separator. The bottom residue was used as carrier oil, and the remaining products were cooled down to room temperature to yield a light and middle distillate net product with a boiling range between 80 and 360 "C. The oil was 99% miscible with n-hexane and had an oxygen content of about 12%. With respect to the energy balance, 59% of the input energy (biomass and hydrogen) was contained in the net product

High-pressure Liquefaction and Hydrotreating: Technical University of Berlin, Berlin, Germany, At the Technical University of Berlin the conversion of biomass was studied in a two-step process. In the first stage, the biomass was extracted with tetralin at 300-400 "C at about 4 MPa pressure. The extract, which yielded about 55%, was mixed again with tetralin and catalytically hydrotreated with sulfided NiMo catalyst at 35 MPa, at temperatures between 300 and 450 "C, and a carrier oil to biomass derived oil ratio of 2. The oil from biomass had an oxygen content below 1% .88

Iron-Catalyzed Pressurized Aqueous Pyrolysis: Ecole Nationale Superieure de Chimie, Rennes, France. Laboratory-scale batch autoclaves were used to study liquefaction of poplar in water slurries at 340 "C. Iron seemed to be an effective additive but was oxidized in the process to Fe304. The addition of other iron additives such as oxalate and hydroxide gave nearly as good

Reviews

results while the addition of oxides or sulfate was ineffective. The addition of chloride had a profound negative effect on the liquid product yields. The iron effect was most useful in slow heatup types of experiments. Fast heatup experiments were found to be more useful for higher yields of oil production (>40% CH2Cll soluble). The use of reducing gas appeared to have little effect on the liquefaction compared to the use of inert gas only at 4-6 MPa initial pressure.miw

Combined Solvolysis and Upgrading: University of Technology, Compiegne, France. An acid-catalyzed phenolic depolymerization of wood was used to liquefy oak in water in 260 O C (30 min at temperature). A secondary hydrotreatment at 330 "C, 30 min, CoMo catalyst, and 2 MPa of hydrogen initial pressure followed to produce an oil product and regenerate the phenol. The process was studied batchwise with batchwise recycle of the upgraded product for up to seven cycles. Water yield was high, 30% on dry wood basis. Gas production and product oil viscosity increased throughout the tests. Phenol consumption continued through the first five cycles and then ceased. Hydrogen consumption was small, <1.5% on dry wood basis. Light product fraction yield was presented as 25% and heavy fraction at 30%. Coke yield was 5% and gas yield was 10%.g1*g2

Alkali-Catalyzed Liquefaction: National Research Insti tute for Pollution and Resources, Tsukuba, Ibaraki, Japan. Extensive testing in batch reactors was performed to evaluate the liquefaction of biomass in water slurries in a pressurized system at 250-400 "C. Many types of wood and several fermentation stillages were tested as feedstock. A heavy oil product which spontaneously separated from the water phase upon cooling was produced in all cases when an alkali-metal carbonate catalyst was added to the system. The typical yield from the stillages at 300 "C was around 50% of an oil containing up to 6% nitrogen with about 35 MJ/kg. The energy content and the mass yield of heavy oil were inversely related; and lower yields of higher energy products were produced at higher temperature or longer residence

Upgrading of Biomass Liquefaction Products Research efforts continue to develop methods of up-

grading both pyrolysis oils and high-pressure liquefaction oils. These efforts include pyrolysate upgrading by catalytic hydroprocessing and by zeolitic catalytic cracking. High-pressure oil upgrading by catalytic hydroprocessing is also being tested. A limited review of this work has already been p u b l i ~ h e d . ~ ~

(79) Bean, F. R.; McAuliffe, C. A. 'Conversion of Municipal Waste to Fuel"; Canadian patent No. 1,164,378, issued March 27, 1984.

(80) Benn, F. R.; McAuliffe, C. A. 'Conversion of Municipal Refuse to Fuel"; UK patent application No. 2,166,1546, filed Sept. 15, 1984.

(81) Bult, J. M. E. "The MANOIL Project", presented at the 89th AMual Conference of the Institute of Wastes Management, Torbay, UK, June 16-19, 1987.

(82) Meier, D.; Larimer, D. R.; Faix, 0. Fuel 1986,65, 910-915. (83) Meier, D.; Larimer, D. R.; Faix, 0. Fuel 1986,66, 916-921. (84) Meier, D.; Fuchs, K.; Faix, 0. In Energy from Biomass and

Wastes X Klaee, D. L., Ed.; Institute of Gas Technology: Chicago, 1987; pp 785-800.

(85) Meier, D.; Faix, 0. In Research in Thermochemical Biomass Conuersion; Bridgwater, A. V. Kuester, J. L., Eds.; Elsevier Applied Science: New York, pp 804-815.

(86) Meier, D.; Faix, 0. Roc . 4th Int. Symp. Wood Pulping Chem., Paris 1987; 2, 407-410.

(87) Meier, D.; Faix, 0. Euroforum New Energies, R o c . Int. Congr., Saarbrucken, FRC, Oct. 24-28 1988,670-672.

(88) Nelte, A.; Meier Zu Kokcker, H. Euroforum New Energies, Proc. Int. Congr., Saarbrucken, FRG, Oct. 24-28 1988,673-675.

(89) Soyer, N.; Hyvrard, F.; Bruneau, C.; Brault, A. In Pyrolysis Oils from Biomass: Producing, Analyzing, and Upgrading; Soltes, E. J., Milne, T. A., Us.; ACS Symposium Series No. 376; American Chemical Societv: Washineton. DC. 1988: DD 220-227.

(9Oj Bestue-Ltibazuy, C.; Soye;,-N.; Bruneau, C.; Brault, A. Can. J . Chem. Eng. 1985,63, 634-638.

(91) Bouvier, J. M.; Gelus, M.; Maugendre, S. In Pyrolysis Oils from Biomass: Producing, Analyzing, and Upgrading; Soltee, E. J., Milne, T. A,, Eds.; ACS Symposium Series No. 376; American Chemical Society: Washington, DC, 1988; pp 129-138.

(92) Bouvier, J. M.; Gelus, M.; Maugendre, S. Appl. Energy 1988,30, A F A R . -- --.

(93) Yokoyama, S.-Y.; Ogi, T.; Koguchi, K.; Nakamura, E. Liq. Fuels

(94) Ogi, T.; Yokoyama, S.-Y.; Koguchi, K. J . Jpn. Pet. Inst. 1985,

(95) Yokoyama, S.-Y.; Ogi, T.; Koguchi, K.; Murakami, M.; Suzuki, A.

(96) Yokoyama, S.-Y.: Suzuki, A,: Murakami, M. Chem. Lett., Chem.

Technol. 1984,2(2), 155-163.

28(3), 239-245.

J . Jpn. Pet. Inst. 1986,29(3), 262-266.

SOC. Jpn. 1966,649452. (97) Yokoyama, S.-Y.; Ogi, T.; Koguchi, K.; Minowa, T.; Murakami,

M.; Suzuki, A. In Research in Thermochemical Biomass Conversion; Bridgwater, A. V., Kueeter, J. L., Eds.; Elsevier Applied Science: New York, 1988; pp 792-803.

Reviews

Two-step Catalytic Hydrotreating of Pyrolysis Oils: Pacific Northwest Laboratory (PNL), Richland, WA. A two-step hydrotreating process was developed for production of hydrocarbon fuels from biomass pyrolysis oils. All studies were performed in a continuously fed 1-L fixed catalytic bed. In the first step, a low-temperature (no "C, 13.8 MPa) catalytic (sulfided cobalt-molybdenum on alumina) treatment was used to process the thermally unstable pyrolysate into a tar similar to the high-pressure liquefaction product. This tar was then hydro- deoxygenated and hydrocracked by conventional hydrotreating techniques (400 "C, 13.8 MPa) to produce gasoline. The use of the sulftded cobalt-molybdenum catalyst at 350 "C and 13.8 MPa in a single-step process with the pyrolysate produced only limited quantities of hydrocarbon product before the catalytic bed plugged with cokelike material.

The low-temperature stabilization of pyrolysis oil was determined to be a catalytic hydrotreating process. Al- though hydrogen consumption was low (30 L/L of oil), operation in the absence of hydrogen eventually led to high levels of coke formation on the catalyst. In the absence of the catalytic metals, the bed plugged almost immedi- ately.WJw

The two-step process was also performed in a single reactor vessel by means of a nonisothermal catalyst bed. In that case the pyrolysate was fed with hydrogen to the bottom of the upflow reactor, which was maintained at low temperature (<300 "C). The feed flowed (0.1 L of oil/L of catalyst/h LHSV) upward into the higher temperature (400 "C) portions of the catalyst bed and exited the top as a mixture of water vapor, hydrocarbons, and carbon oxide gases. Yields of 0.4 L/L of oil of a hydrocarbon liquid (<1% oxygen) were achieved.lol A similar suc- cessful test was performed with a peat-derived pyrolysate, and gasoline-range hydrocarbons were produced.lo2

Catalytic Hydroprocessing of Updraft Gasifier Oils: Texas A&M University, College Station, TX. Experimentation involved both batch reactor studies and trickle-bed tests. Twenty different catalysts were tested in the batch reactor with either a decalin or methylcyclo- hexane solvent system for pine pyrolysate. Nobel metal catalysts (5% Pt or Pd on support) generally gave superior results in hydrocarbon conversion and water yield compared with more conventional hydrotreating catalysts. Trickle-bed experiments were used to study the effects of reaction temperature, pressure, and space velocity on oxygen removal from pine pyrolysate in decalin solvent. The Pt/A1,03 catalyst exhibited the best activity for oxygen removal, while the Ni-W catalyst was dropped from further study because of its inactivity. The results were modeled, and a clear trend of the effect of pressure and temperature on oxygen removal was noted; however, space velocity had no clear effect.

The trickle-bed reactor consisted of an 81.3-cm-long 316 SS tube. The bottom 30.5 cm contained an inert support with the top 50.8 cm packed with catalyst. The bottom

Energy & Fuels, Vol. 5, No. 3, 1991 405

55.9 cm of the reactor was immersed in a salt bath so that the bottom half of the catalyst bed was a t uniform temperature. A t the same time the temperature of the non- immersed top half decreased linearly from near the reaction temperature at the top of the salt bath to 190 O C at the top of the reactor. Typical operating conditions were hydrogen feed of 100 mL/min per gram of pyrolysate oil at 5.2-10.4 MPa; liquid feed diluted at 2 g of decalin per gram of pyrolysate oil; weight hourly space velocities of 0.5-3.0 g oil/(g of catalyst h); and temperature of 400 "C with a catalyst load of 60 g.lo3JM

Catalytic Hydrotreating: Universit6 Catholique de Louvain, Louvain, Belgium. Two different pyrolysis oils produced at the pyrolysis unit in Raiano, Italy, and operated by Alten Consortium were hydrotreated in a batch reactor. The catalysts tested at typical hydrotreating conditions were CoMo, NiMo, and NiMo on a phospho- rus-treated alumina support. One of the oils was produced from wood and contained 30% oxygen; the other was produced from olive husks, a lignin-rich material, and contained 15% oxygen and 3% nitrogen.

The hydrotreatment was effected in two stages (at 250 and 380 "C), but the wood-derived oil showed only a very limited upgrading because the batch reactor did not allow optimal contact time. Under the same conditions the olive-husk-derived oil showed 70% hydrodeoxygenation but only 58% hydrodenitrogenation. With this oil the hydrogen consumption rate was very high above 230 "C. Wood-derived oil showed good conversion only in the presence of a hydrogen donor solvent (tetralin). The difference in the reactivity of the oils may be due to the oxygen content and the nature of the oxygenated functional groups; in fact, the olive-husk-derived oil consisted mostly of phenolic hydroxyl with a very low acid content. This study reemphasized that the nature of the oils to be treated is very important and suggested that bio-oils derived from lignin constitute the best feed for hydrotreatment.106J0e

Catalytic Hydrotreatment of Fast Pyrolysis Lig- nins: University of Waterloo, Waterloo, Ontario, Canada. Catalytic hydrotreatment has been undertaken in a continous-flow reactor with the lignin-derived pyrolysis fraction from the Waterloo Fast Pyrolysis Process. A nonisothermal catalyst bed was used containing sulfided CoMo catalyst. Reported yields were 6144% of light organic liquids (0.5% oxygen, by difference) from the pyrolytic lignin; pyrolytic lignin was 21.2% of the original hog fuel feed. A substantial aromatic content (38% aromatic carbon by 13C NMR) remained in the upgraded product with naphthenes and hydroaromatics also prom- inent.lo7

Low-Pressure Zeolitic Upgrading: SERI, Golden, CO. An altrenative to the high-pressure upgrading of the pyrolysis oil is to use zeolite catalysts at atmospheric pressures without added hydrogen. Although the molecular weight of the condensed pyrolysis oils has been found typically to be between 500 and 2000, researchers at SERI determined that the pyrolysis vapors generally had much lower molecular weights, less than 200. The molecular size ~~

(9s) Elliott, D. C. In Research in Thermochemical Biomass Conuer- eion; Bridgewater, A. V., Kuester, J. L., Eds.; Elsevier Applied Science: New York, 1988, pp 1170-1176.

(99) Elliott, D. C.; Baker, E. G. In Energy from Biomass and Waste X , Klaes, D. L. Ed.; Institute of Gae Technology: Chicago, 1987; pp 765-784.

(100) Elliott, D. C.; Baker, E. G. 'Process For Upgrading Biomass Pyrolyzates"; U.S. patent No. 4,795,841, issued January 3, 1989.

(101) Baker, E. G.; Elliott, D. C. In Research in Thermochemical Biomass Conuersion; Bridgwater, A. V., Kuester, J. L., Eds.; Elsevier Applied Science: New York, 1988; pp 883-895.

(102) Elliott, D. C.; Baker, E. G.; Piskon, J.; Scott, D. S.; Solantaueta, Y. Energy Fuels 1988,2, 234-235.

(103) Soltes, E. J.; Lin, S-C. K. Progress in Biomass Conversion; Ac- ademic Press: New York, 1984; Vol. V, pp 1-68.

(104) Soltes, E. J.; Lin, 5-C. K.; Sheu, Y-H. E. Prepr. Pap.-Chem. 1987, 32(2), 229-239.

(105) Churin, E.; Grange, P.; D+non, B. EEC Contract EN3B-0097-B, Final Report; European Economic Community: Brussels, 1990.

(106) Chur!n, E.; Maggi, R.; Grange, P.; Delmon, B. In Research in Thermochemrcal Bcomass Conversion; Bridgwater, A. V., Kueeter, J. L., Eds.; Elsevier Applied Science: New York, 1988; pp 896-909.

(107) Piskon, J., Majereki, P., Radlein, D., Scott, D. S. Energy Fuels 1989,3,723-726.


and shape of most of the identified compounds were small enough to enter the H-ZSM-5 pore. Preliminary experiments with H-ZSM-5 catalyst confirmed that a small amount of catalyst was sufficient to change the product slate from the oxygenated pyrolysis vapors to a highly aromatic gasoline product. This process has been studied extensively by using the molecular beam/mass spectrom- eter (MB/MS), which allowed the product slate to be ex- amined in real time as the catalyst aged in a fixed bed of 10 g of H-ZSM-5 catalyst. A process variable study was conducted to identify optimal operating conditions, which were found to be quite different from those used to convert methanol to gasoline. Empirical equations were fit to the data to result in parametric contour plots illustrating the effects of the process variables on the yields. Hydrocarbon product yields, including olefins, were around 15 wt % of the dry feed, when steam was used as the carrier gas, at a weight hourly space velocity of between 1 and 4 g of wood/(g of catalyst-h) at 525 0C.108-110 Concurrently, research has been conducted with a larger fEed-bed reactor having 100 g of catalyst and fed a small slipstream of fresh pyrolysis vapors directly from the vortex reactor at SERI.111J12 Hydrocarbon yields, including olefins, from the slipstream reactor have been 20-25%, including 3 4 % heavy oils.113 Recent research has been directed toward recovery of the gaseous olefins as part of the gasoline product. The gasoline produced consists primarily of al- kylated benzenes, e.g., toluene, xylenes, ethylbenzene, and isopropylbenzene (~umene)."~

Catalytic Processing of Vaccum Pyrolysis Oils: Laval, Sainte-Foy, Quebec, Canada. Processing similar to the SERI work was performed at Laval with vacuum pyrolysis oil fractions. In the Laval setup, the pyrolysis condensates were preheated in helium and swept into the bed of 1.0 f 0.2 g of H-ZSM-5. Six pyrolysis fractions were tested a t temperatures from 350 to 450 "C and LHSV of 0.5-2.5 h-l. Products including gases, coke, C5X10, BTX, oxygenates, and residuum were collected, quantified, and analy~ed."~

In a related study, low-temperature catalytic hydrotreatment of the vacuum pyrolysis oil was performed. A 5% Ru on y-alumina catalyst was used at 80-140 "C with up to 2 h at temperature for an initial hydrogenation/ stabilization step. A subsequent batch step of hydrodeoxygenation at 350 "C was performed with a COO-W03 on y-alumina catalyst to produce an upgraded oil product (<lo% oxygen content). Other experiments showed that

Reviews

copper chromite was an ineffective hydrogenation catalyst for the vacuum pyrolysis oils."6

Catalytic Hydrotreatiag/Hydrocracking: PNL, Richland, WA. Catalytic hydrotreatment of high-pressure liquefaction oils was also studied at PNL using the continuous-feed, fixed-bed reactor. Commercial hydrotreating catalysts (sulfided CoMo or NiMo on Al,OJ and conditions (350-400 OC and 13.8 MPa of H2) were used to hydrodeoxygenate and hydrocrack the biocrude oils. The hydrocarbon product, primarily gasoline-range cyclic al- kanes and aromatics (75 octane [R + M]/2), was produced in high yields; however, low space velocities were required (0.1). At high space velocities (OS), a low oxygen, highly aromatic crude oil was produced. Cracking and hydrogenation of the higher molecular weight components were concluded to be the rate-limiting steps in the upgrading process.

Advanced processing configurations were also studied, including two-stage hydrotreating with hydrocracking of heavy product and hydrotreating with recycle of heavy components. Initial tests indicated that both systems could improve the processing rate and reduce hydrogen consumption. The combined hydrotreating and hydrocracking systems also had increased yields of gasoline-range material. Improved catalysts for the hydroprocessing were identified as a key to process i m p r o ~ e m e n t . ~ ~ ~ - ~ ~ ~

Catalytic Hydrotreating: University of Toronto, Toronto, Ontario, Canada. Upgrading studies through catalytic hydrotreatment of model compounds has been undertaken in a batch reactor system. Early tests were made with a nonsulfided NiMo on alumina catalyst with phenol and anisole as the feedstocks." A more in-depth study of phenolics, including different isomers of di- hydroxybenzenes, methoxyphenols, and methylphenols, was also reported.l2I Since the NiMo catalyst was used in the oxide form, much higher temperatures were required in the tests, 350-500 "C, than reported in the bio-oil treatment work by others.

Zeolitic Processing of Bio-oils: University of Sas- katchewan, Saskatoon, Saskatchewan, Canada. Re- search was undertaken on the upgrading of biomass-derived oils to fuels and chemicals using zeolite (ZSM-5) catalyst. Wood-derived high- and low-pressure pyrolysis oils, plant/vegetable oils (flax, sunflower, canola, etc.), and tall oil (derived from soap skimmings recovered from black liquor from Kraft pulping operation) were tested. Ex- periments were conducted in a microreactor operating at temperatures from 370 to 520 OC and atmospheric pressure.122-124 Recent experiments with feeding tetralin with both high-pressure pyrolysis oils and fast pyrolysis oils

(116) Gagnon, J.; Kaliaguine, S. Ind. Eng. Chem. Res. 1988, 27,

(117) Elliott, D. C.; Baker, E. G. Proceedings of the 20th IECEC, Society of Automotive Engineers: Warrenton, PA, 1985; Vol. 1, pp 586-594.

(118) Baker, E. G.; Elliott, D. C. In Pyrolysis Oikr from Biomass: Producing, Analyzing, and Upgrading; Soltes, E. J., Milne, T. A., Eds.; ACS Symposium Series No. 376; American Chemical Society: Wash- ington, DC, 1988; pp 228-240.

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278-284. (123) Prasad, Y. S.; Bakhshi, N. N. Can. J . Chem Eng. 1986, 64,

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1988; SERI CP-231-3355; pp 45-56. (120) K i lury, R. K. M. R.; Tidwell, T. T.; Boocock, D. G. B.; Chow,

(108) Evans, R. J.; Milne, T. A. In Pyrolysis Oils from Biomass: Producing, Analyzing, and Upgrading; Soltes, E. J., Milne, T. A., Eds., ACS Symposium Series No. 376; American Chemical Society: Wash- ington, DC, 1988; pp 311-327.

(109) Evans, R. J.; Filley, J.; Milne, T. A. Thermochemical Conversion Program Annual Review Meeting; Solar Energy Research Institute: Golden, CO, 1988; SERI/CP-231-3355; pp 33-43.

(110) Milne, T. A.; Evans, R. J.; Filley, J. In Pyrolysis Oils from Biomass: Producing, Analyzing, and Upgrading; Soltes, E. J., Milne, T. A., Eds.; ACS Symposium Series No. 376; American Chemical Society: Washington, DC, 1988, pp 910-926.

(111) Diebold, J. P.; Scahill, J. W. In Pyrolysis Oils from Biomass: Producing, Analyzing, and Upgrading; Soltes, E. J., Milne, T. A., Eds.; ACS Symposium Series No. 376; American Chemical Society: Wash- ington, DC, 1988; pp 264-276.

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Thermochemical Biomass Conversion; Bridgwater, A. V., Kuester, J. L., Eds.; Elsevier Applied Science: New York, 1988; pp 927-940.

(114) Diebold, J. P.; Scahill, J. W. Thermochemical Conversion Pro- gram Annual Review Meeting; Solar Energy Research Institute: Golden,

(115) Renaud, M.; Grandmaison, J. L.; Roy, C.; Kaliaguine, S. In Py- rolysis Oils from Biomass: M w i n g , Analyzing, and Upgrading; Soltea, E. J., Milne, T. A., Eds.; ACS Symposium Series No. 376; American Chemical Society: Washington, DC, 1988, pp 290-310.

CO, SERI/CP-231-3356; 1988, pp 21-32.

Reviews

showed some advantages over the ZSM-5 catalyst.'% Extraction and Catalytic Processing: Chalmers

University of Technology, Giiteborg, Sweden. Oil from high-pressure directly liquefied biomass (PERC TR-12 from the Albany facility) was upgraded to transportation fuels by various methods. Extraction of the crude TR-12 oil to remove the salts and heavy organics was followed by hydroprocessing, distillation, and catalytic cracking. The yields of transportation fuels were low, 35%, because of the low yield in the initial extraction step. However, it was clearly shown that transportation fuels could be produced by this

Extraction was performed with several solvents to produce different fractions of the TR-12 oil. The fractions were then catalytically treated to determine if the deactivation of the hydroprocessing catalyst varied among the fractions of the crude oil. However, it was shown that only desalting was necessary to eliminate the deactivation effect (the TR-12 oil contains about 1% sodium as salts). In the first hours in a run, high-surface-area catalyst designed for hydrodesulfurization showed higher activity than a catalyst with large pores produced for hydrodemetallization. However, deactivation was lower with the large-pore cat-

The reactivity and reaction path for hydrodeoxygenation of methyl-substituted phenols was studied with sulfided cobalt-molybdenum on alumina catalyst. The reaction proceeded through two paths, and two active sites for the two paths were suggested.'%

Hydrotreatment of Lignins: SERI, Golden, CO. The aim of this research was the development of mild hydrotreating processes to produce phenols from lignin for methyl aryl ether synthesis to produce gasoline blending agents. Batch and semicontinuous laboratory reactor experiments were performed with lignin and model compounds. Catalyst development was a primary goal of the project; use of a more acidic support for the catalyst was identified as a potentially valuable area of re~earch. '~J~ '

Other Biomass Liquefaction Research Centralized Analysis/Chemical Recovery: British

Columbia Research, Vancouver, British Columbia,

alyst.134

Energy & Fuels, Vol. 5, No. 3, 1991 407

Canada. British Columbia Research conducted centralized analytical studies of liquid products, byproducta, and wastes produced from direct conversion research at other facilities in Canada and the USA. The product analysis included standard physical properties, as well as more detailed and specific studies such as analysis of polycyclic aromatic hydrocarbons by gas chromatography/mass spectrometry, identification and quantification of chemicals in biomass oils, and use of nuclear magnetic resonance to characterize products.lM

Research was also under way on methods for recovery of chemicals from biomass-derived oils and from waste aqueous phases associated with the processes. One program studied the recovery of levoglucosan, and a second program studied the recovery of industrial chemicals such as hydroxyacetaldehyde, hydroxyacetone, formic acid, acetic acid, and mixed calcium formate, acetate, and propionate (for road d e i ~ e r ) . ' ~ ~ J ~

Oil Product Analysis: PNL, Richland, WA. Other supporting research completed at PNL involved analysis of biomass liquefaction product oils. Essentially two projects were involved; one dealt with detailed analysis of pyrolysate condensates from various process systems and the second was a chemical analysis of oils produced by high-pressure liquefaction of several types of nonwoody biomass. The pyrolysate study identified a continuum of chemical functional types produced as a function of pyrolysis temperature. Biological activity of the pyrolysates was also correlated with temperature of formation and attributed primarily to the formation of polycyclic aromatic hydrocarbons at higher temperatures. Flash pyrolysis oils produced at temperatures around 500 "C were found to have immeasurably low activity as mutagens or tumorigens whereas pyrolysis tars formed at higher temperatures were progressively more car~inogenic . '~~J~~

Oil compositions formed from nonwoody biomass were found to have many similarities to the wood-derived oils. Nitrogen incorporation into the oils resulting from nitrogen in the feedstock was identified as a major difference. Fatty acids and fatty-acid-derived hydrocarbons were also identified in some of the oils.la

Pyrolysis Vapor Analysis: SERI, Golden, CO. Direct MB/MS sampling of the vapors allowed real time analysis of complex gas-phase species, Le., the pyrolysis products and revaporized pyrolysis or liquefaction oils. Most conversion routes could be adequately described by a combination of the major solid-phase and gas-phase pathways:

the two classes of carbohydrate primary pyrolysis pathways, transglycosylation and alkali-catalyzed glycosidic fission;

the two classes of lignin primary pyrolysis pathways, the prompt formation of alkenyl methoxyphenols (such as

(125) Bakehi, N. N.; Furrer, R. M.; Sharma, R. K. In Proceedings of the Seventh Canadian Bioenergy R&D Seminar, Hogan, E., Ed.; Energy, Mines, and Resources Ministry: Ottawa, Canada, 1989; pp 687-692.

(126) Gevert, S. B. In Energy from Biomass and Wastes X f i Klass, D. L., Ed.; Institute of Gas Technology: Chicngo, 1988; pp 948-974.

(127) Gevert, S. B.; Otterstedt, J-E. In Energy from Biomass and Wastes X Klaes, D. L. Ed.; Institute of Gas Technology: Chicago, 1987; pp 845-854.

(128) Gevert, S. B.; Otterstedt J-E. Biomass 1987,13,105-115. 11291 Gevert. S. B.: Otterstedt J-E. Biomass 1987.14.173-183. (130) Otters&dt,-J-E.; Gevert, S. B.; Sterte, J. Prepr. Pap.-Am.

(131) Otteretedt J-E.; Gevert, S. B.; Sterta, J. Fluid Catalytic Crack- Chem. Soc., Diu. Pet. Chem. 1987,32(3), 692-694.

ing; ACS Symposium Series No. 375; American Chemical Society: Washington, DC, 1988, Chapter 17.

(132) Gevert, S. B. Determination of Oxygen in Organic Materials. Preaented at the Pittaburgh Conference on Analytical Chemistry and Applied Spsctroecopy, Atlantic City, NJ, March 1986; Paper 53.

(133) Gevert, S. B. Upgrading of Directly Liquefied Biomass to Transportation Fuels. Ph.D. thesis, Chalmers University of Technology, Gothenburg, Sweden, 1987.

(134) Gevert, S. B.; Andersson, A.; JBrAs, S. G.; Sandquist, S. Prepr. Pap.-Am. Chem. Soc., Div. Fuel Chem. 1988, 39(4), 913-919.

(135) Gevert, 8. b.; Otterstedt, J-E.; Maseoth, F. E. Appl. Catal. 1987, 31,119-131.

(136) Ratcliff, M. A.; Johnson, D. K.; Poeey, F. L:; Chum, H. L. Ninth Symposium on Biotechnology for Fuels and Chemicals; Humana Press: Clifton, NJ, 1987; pp 151-160.

(137) Ratcliff, M. A.; Johneon, D. K.; Posey, F. L.; Maholland, M. A.; Cowley, S. W.; Chum, H. L. In Research in Thermochemical Biomass Conversion; Bridgwater, A. V., Kuester, J. L., Eds.; Elsevier Applied Science: New York, 1988; pp 941-955.

(138) McKinley, J. Biomass Liquefaction: Centralized Analysis; Final Report, DSS File No. 232-4-6192; Energy, Mines and Reeources Ministry Ottawa, Canada, 1988.

(139) Longley, C. In Proceedings of the R&D Contractors Meeting on Biomass Liquefaction; Hogan, E., Ed.; Energy, Mines, and Resources Ministry: Ottawa, Canada, in press.

(140) Oehr, K. In Proceedings of the R&D Contractors Meeting on Biomass Liquefaction; Hogan, E., Ed.; Energy, Mines, and Resources Ministry: Ottawa, Canada, in press.

(141) Elliott, D. C. "Analysis and Comparison of Biomaes Pyrolysis/ Gasification Condenaates". Final Report PNL-5943; Pacific Northwest Laboratory: Richland, WA, 1986.

(142) Elliott, D. C. In Pyrolysis Oils from Biomass: Producing, Ana- lyzing, and Upgrading; Soltes, E. J., Milne, T. A., Eds., ACS Symposium Series No. 376; American Chemical Society: Washington, DC, 1988; pp 55-65.

(143) Elliott, D. C.; Sealock, L. J., Jr.; Butner, R. S . Prepr. Pap.-Am. Chem. Soc., Diu. Fuel Chem. 1987,32(2), 186-194.


coniferyl alcohol) and the later formation of low-molecular-weight aromatics (such as guaiacol); and

the four zones of gas-phase processes, primary product preservation below 500 "C, slight cracking of thermally labile species from 500 to 600 OC, secondary reactions from 600 to 750 "C forming simple phenols, and tertiary reactions from 750 to lo00 "C forming polycyclic aromatics.

Over 50 different samples of biomass and RDF were pyrolyzed and analyzed by the MB/MS scanning over the mass ranges of 10-250. Multivariate analysis of this very extensive data set was used to determine that there were 13 factors that explained over 90% of the variance in the data. Interpretation of the data resulted in the identification of six major chemical compound classes to explain the 13 factors.

To determine the effect of process variables, a statis- tically designed set of experiments was conducted to look at the effects on the six compound classes identified in the feedstock screening tests. Empirical equations were fitted to the data and used to generate parametric plots showing the effect of different variables.1m*14-1M

International Energy Agency Thermochemical Round Robin Analysis. The first IEA Thermochemical Round Robin was organized as part of an IEA Voluntary Standards Activity. The objective of the study was to determine the variability associated with the measurement of carbon, hydrogen, oxygen, and water in biomass oils using those techniques normally employed at each laboratory. Two biomass oil samples were distributed to 15 laboratories in November 1988. One sample was a low- oxygen-content condensed oil (PERC TR-12 oil from the Albany facility), and the second was a primary oil (fast pyrolysis oil from University of Waterloo) with a high oxygen and water content.

The precision for carbon was excellent, whereas both the hydrogen and oxygen values were more variable. The water content was quite variable, and it had a strong in- fluence on the carbon and hydrogen estimates (on a dry basis) which in turn had a significant effect on the H/C ratio of the biomass oil. The coefficients of variation for the H/C ratios of the two oils were markedly different in that the PERC oil had a value of 5%, which was in the range anticipated, while that of the Waterloo oil was 19.5% .14'

Chemical Mechanisms Studies: PNL, Richland, WA. Research on chemical mechanisms of biomass com- ponent conversion to oil has continued as part of the Basic Energy Sciences Program of the U.S. DOE. Experimental conditions focused on aqueous processing in neutral or base-catalpd conditions. Conversion of cellulose pyrolysis products to aromatics in the presence of alkali was well documented. Acidic processing conditions have been identified as existing in both alkali-catalyzed and uncatalyzed experiments; the pH is higher (4-5) in the alkali-catalyzed systems compared with 2-3 in the uncatalyzed systems.1qg162

Reviews

Other Studies. Results of several other, more basic studies of the pyrolysis of biomass were reported at a symposium, Production, Analysis and Upgrading of Py- rolysis Oils from Biomass, at the national meeting of the American Chemical Society, April 5-10, 1987, in Denver, CO. These results were reported in the Preprints of the Fuel Chemistry Division (American Chemical Society: Washington, DC, 1987), Vol. 32, No. 2. Among these results is a study of the products of low-temperature (250 "C) pyrolysis of biomass (Degroot et al., pp 36-43); chemistry of secondary reactions in pyrolysis (Boroson et al., pp 51-58); coliquefaction of lignin and coal (Altieri and Coughlin, pp 117-128); pyrolytic reactions in supercritical solvents (Simkovic et al., pp 12s132; Townsend and Klein, pp 133-142); particle size and moisture effects on pyrolysis (Kelbon et al., pp 44-50); alkaline degradation of sac- charides to organic acids (Krochta et al., pp 148-156); pyrolysis products from municipal solid waste components (Helt and Agrawal, pp 82-89); the melting-like charac- teristic of pyrolyzing biomass (Lede et al., pp 59-67); and zeolitic cracking of pyrolysis liquids and related compounds in a fluidized bed (Chen et al., pp 264-275). The last five of these can also be found in expanded form in Pyrolysis Oils from Biomass: Producing, Analyzing, and Upgrad- ing; ACS Symposium Series No. 376; American Chemical Society: Washington, DC, 1988.

Technoeconomic Assessments IEA Working Group: Canada, Finland, Sweden,

USA. A major emphasis of the IEA Working Group has been the technoeconomic assessment of the biomass liquefaction processes under development in the laboratories in the participating countries. The original assessment, completed in 1984,153 concluded the following:

High thermal efficiencies were obtainable by these biomass liquefaction processes.

Flash pyrolysis was the most promising process for the production of a fuel oil for combustion purposes.

The process costs are highly sensitive to feedstock cost. Technical uncertainties because of the early state of

development made comparisons impossible for upgrading processes. Further research was recommended for the processes and processing equipment, especially for the primary oil upgrading step.

During the second stage of the IEA project, a more detailed assessment of the biomass liquefaction process was undertaken including primary liquefaction, upgrading of the primary oil by hydrotreating, and final refining of the upgraded oil to market p rodu~ t s .~J" J~~ That study concluded the following:

The high efficiencies and the feedstock cost sensitivities found in the first stage were reaffirmed.

Flash pyrolysis was identified as the most economical

(144) Evans, R. J.; Milne, T. A. Energy Fuels 1987,1,123-137. (145) Evans, R. J.; Milne, T. A. Energy Fuels 1987, 1,311-319. (146) Evans, R. J.; Milne, T. A. In Research in Thermochemical

Biomass Conuersion; Bridgwater, A. V., Kuester, J. L., Eds.; Elsevier Applied Science: new York, 1988; pp 264-279.

(147) Overend, R. P.; McKinley, J. W.; Eltiott, D. C. Readta of the IEA Round Robin on the Ultimate halys is of Two Biomass Pyrolysis Oils. Presented at the American Chemical Society National Meeting, Boston, April 22-27, 1990.

1986, 27, 3091.

1, 239.

11.

(148) Samuels, W. D.; Nelson, D. A.; Hallen, R. T. Tetrahedron Lett.

(149) Nelson, D. A.; Samuels, W. D.; Hallen, R. T. Energy Fuels 1987,

(150) Nelson, D. A.; Hallen, R. T. J . Anal. Appl. Pyrolysis 1987, 12,

(151)Theander, 0.; Nelson, D. A. Adu. Corbohydr. Chem. 1988, 46,

(152) Nelson, D. A.; Hallen, R. T.; Theander, 0. In Pyrolysis Oils from Biomass: Producing, Analyzing, and Upgrading; Soltes, E. J., M h e , T. A., ME.; ACS Symposium Series No. 376; American Chemical Society: Washington, DC, 1988; pp 113-118.

(153) McKeough, P.; Nissili, M.; Solantausta, Y.; Beckman, D.; Ostman, A.; Bergholm, A.; Kannel, A. 'Techno-Economic Assessment of Selected Biomass Liquefaction Processes. IEA Cooperative Project D1, Biomass Liquefaction Teat Facility Project"; Final Report, DOE/NBM- 1062-Vol. 5; National Technical Information Service: Springfield, VA, 1988.

(154) Elliott, D. C.; Baker, E. G.; Beckman, D.; Solantaueta, Y.; Tu- lenheimo, V.; Gevert, B.; Hdmell, C.; btman, A.; KjellsMm, B. B t o m s

273-326.

1990,22(1-4), 251-270. (155) Elliott, D. C.; Baker, E. G.; Beckman, D.; Solantaueta, Y.; Tu-

lenheimo, V.; Ostman, A.; Gevert, B.; Hdmell, C.; KjehWm, B. In Energy from Biomass and Waste XIII: Klaas. D. L.. Ed.: Institute of Gaa Technology: Chicago, 1990; pp 743-768.

Reviews Energy & Fuels, Vol. 5, No. 3, 1991 409

conversion process covered all stages from biomass re- ception, storage and handling, through conversion, product synthesis, and refining. Feedstocks included wood, straw, and prepared MSW; products included methanol, fuel alcohol, gasoline (via two routes), and diesel. The model also included biochemical conversion processes for ethanol production.

The model was based on mass and energy balance over significant process steps that could be sequentially combined to give an overall process based on logical rules. Each process step also included a capital cost estimation model. On completion of a mass and energy balance for a complete process, the total capital cost was estimated by summing process step costs, and the product cost was then estimated. In addition, various detailed energy balance and cost estimates were also produced. A major feature of this model was that a consistent comparison of technologies could be undertaken to aid in determining preferred processes, feeds, or products.

Technoeconomic assessments of smaller scale plants to produce pyrolysis liquids and char slurries were also carried out to compare alternative technologies, feedstocks, and products from 1 to 10 ton/h scale units.182 The work was extended to cover environmental and social costs and benefits in the context of the EEC Leben projects to provide more robust justification for early implementation of those technologies."

In addition, a comprehensive world-wide database of thermochemical biomass conversion activities was assem- bled.'MJa About 650 activities were identified and information collated on the technical and commercial status of each one.

Future Directions for the Technology In recent years the development of alternative sources

of liquid fuels has slowed dramatically as research funding sources have been reduced in response to the apparent oversupply of petroleum and resultant lower prices. However, the interlude will undoubtedly be short before more price shocks are seen in the market because of the continually increasing demand and diminishing supply of oil.

During the period just before this review's time frame, North American and Scandanavian research support was strong, and as a result the main research efforts were found in Canada, Finland, Sweden, and the USA. Now the major funding for future research efforts is found in the European Community. Without major shifts in government funding of research in the USA and Canada, in a few years the next review of the state-of-the-art of biomass liquefaction could be dominated by the work being initiated under the EC JOULE ~ r 0 g r a m . l ~ ~ Biomass liquefaction provides one alternative to petroleum as a source of both liquid fuels and chemicals. The research described in this article has as its collective goal the development of processes for the economical production of these valuable products.

The research has shown that reactor systems can be designed to efficiently produce liquid products from biomass. The chemical compositions of the liquids have been studied in detail. Upgrading processes have been

process both for production of primary fuel oil and for gasoline production.

Significant development and cost reduction potential exists for both high-pressure liquefaction and flash pyre lysis.

The upgrading step remains the less developed, more uncertain step, with catalyst lifetime being the most important factor. Therefore, the Working Group recommended that future development of the flash pyrolysis process be emphasized.

Economic Evaluation of Emerging Pyrolysis Pro- cesses: SA1 Corp., McLean, VA. A continuing effort within the US. DOE, Thermochemical Conversion of Biomass program, has been the SA1 economic evaluation work. The SA1 group has evaluated the liquefaction processes under development in the U S . from several assumption bases. The first studylM of the Georgia Tech Entrained Flow Pyrolysis process concluded (1) the production of oil product from wood seems to be cost com- petitive with current fuel oil selling prices (around $4.5/ million Btu); and (2) oil production costs are highly sensitive to feedstock cost and oil yield but less sensitive to capital cost and byproduct char credit. The study recommended further development of the process and upgrading procedures to produce high-quality liquid fuels.

A second effort by SAI was a comparison of the Georgia Tech Entrained Flow process incorporating catalytic hydrotreating for gasoline production and the ablative pyrolysis system from SERI with their zeolite cracking upgrading process. That studylS7 concluded the following:

Entrained flow pyrolysis with catalytic hydrotreating maximized gasoline yield and had a higher thermal efficiency.

Ablative pyrolysis with zeolitic cracking had a lower capital requirement but also a lower yield and efficiency.

Current costs for the gasoline product were around $2/gal but future potential developments could reduce costs to under $l/gal for both processes. The study recommended further development of both process types. In a second version, the evaluation was further refined,lM but the conclusions were unchanged.

A final analysis by SA1 compared direct liquefaction costs with indirect liquefaction (methanol from biomass gasification) costs. On an energy basis, the methanol costs were similar to the direct liquefaction gasoline product cost in the present case, but the direct liquefaction technologies exhibited much greater potential for cost reduction based on potential process devel~pments. '~~

Technoeconomic Assessments: Aston University, Birmingham, UK. A process simulation with an integral cost estimation computer model was developed for the production of liquid fuels from biomass by direct and indirect thermochemical conversion routes.lmJsl The

(156) Wan, E. I. Proceedings of the 1985 Biomass Thermochemical Conversion Contractors' Meeting; Pacific Northwest Laboratory: Rich-

(157) Wan, E. I.; Fraeer, M. D.; Kwartang, I. K. Proceedings of the 1987 Biomass Thermochemical Conversion Contractors' Meeting; Pacific Northwest Laboratory: Richland, WA, 1987; P?SA-l5482;,pp 115-140.

(158) Wan, E. I.; Fraser, M. D. Thermochemtcal Conversion Program Annual Review Meeting; Solar Energy Research Institute: Golden, CO,

(159) Wan, E. I.; Fraeer, M. D. In Research in Thermochemical Biomass Conversion; Bridgwater, A. V., Kuester, J. L., Eds.; Elsevier Applied Science: New York, 1988, pp 61-76.

(160) Bridgwater, A. V.; Double, J. M. In Research in Thermochemical Biomass Conversion; Bridgwater, A. V., Kuester, J. L., Eds.; Elsevier Applied Science: New York, 1988, pp 98-110.

(161) Bridgwater, A. V.; Double, J. M. Non-Waste Technology; VTT Symp. 102; Technical Research Centre: Ekpoo, Finland, 1989; Vol. 1, pp

land, WA, 1986; PNL-SA-13571; pp 167-192.

1988, SERI/CP-231-3355; pp 111-120.

127-144.

(162) Bridgwater, A. V. Proceedings of the 25th IECEC; American Institute of Chemical Engineers: New York, 1990; Vol. 5, pp 107-112.

(163) Graasi, G.; Bridgwater, A. V. Proceedings of the 25th IECEC; American Institute of Chemical Engineers: New York, 1990; Vol. 5, pp 126-1 30.

(164) Bridgwater, A. V.; Double, J. M.; Bridge, S. A. In Research in Thermochemical Biomss Conuersion; Bridgwater, A. V., Kueeter, J. L., Eds.; Eleevier Applied Science: New York, 1988; pp 46-60.

(165) Bridgwater, A. V. Biomass 1990,22(1-4), 279-292.


identified to further transform these liquids into directly marketable fuels. Other methods are being studied for the separation of useful chemic&. International cooperation and exchange of information has played a paramount role in the ability of the world research community in biomass liquefaction to maximize its return on limited budgets. However, there are significant developments that still lie in the future because of the limited effort expended on the research of these processes. These developments are summarized below:

Large-scale demonstration of the liquefaction and upgrading processes, including the support systems such as aqueous and gaseous byproduct handling. The operation of the U.S. DOE Biomass Liquefaction Experimental Fa- cility at Albany, OR, was a short-lived effort that remains, 10 years later, the largest scale attempt a t biomass high- pressure liquefaction at a throughput of 18 kg of wood/h. Larger versions of inefficient, slow pyrolysis process units, which do not maximize liquids production, are in operation in Europe, but scale-up of fast pyrolysis is still in the early stages.

Completion of the refinery cycle to produce murketable liquid fuels from biomass for testing and evaluation. Although hydrocarbon fuels have been produced on the bench-scale and octane measurements made with wood- derived gasolines, complete testing and evaluation of the fuels has yet to be achieved.

Demonstration of chemical separation technologies. Chemicals separation from biomass liquids has been studied both as a means of specialty chemical production and also as a commodity chemical route. Actual separa- tions remain in early development stages.

Determination of the compatibility of biomass liquefaction products with existing petroleum refinery systems. The question of the scale of operation of biomass liquefaction is still debated. Incorporation of the biomass liquefaction product into the commercial liquid fuels production stream could occur at any of several points in the

Reviews

process. Siting of several biomass liquefaction points feeding to a central upgrading plant which then sends its product to a petroleum refinery is one concept to maximize the economic advantages of scale.

Investigation of the potential for controlling the liquefaction process to maximize production of specific products. Some research has been performed to determine the effect of processing parameters on the chemical com- position of the biomass liquefaction product. Continued work in this area may lead to significant developments in tailoring the liquefaction product for specific chemical or fuel needs.

Development of biomass production systems that are coordinated with the liquefaction process requirements to maximize the overall efficiency of the solar energy conversion process. Possible process advantages still remain to be explored in the area of optimization of the biomass growing and harvesting process with the biomass liquefaction process. Better coordination between researchers in each field is needed to identify options for modifying either the liquefaction process or the biomass production process to improve the overall system efficiency. Continued research on biomass liquefaction processes should address these issues in order that alternative liquid fuels and chemicals will be available to meet future needs.

Acknowledgment. The authors acknowledge the support of their respective government agencies for the International Energy Agency programs and the Bioenergy Liquefaction Activity, specifically. The supporting government agencies are Energy, Mines and Resources, Can- ada; European Community Directorate for Research in Science and Technology; Ministry of Trade and Industry, Finland; National Committee for Nuclear and Alternative Energy, Italy; Energy Technology Support Unit, UKAEA, United Kingdom; and Department of Energy, United States.

Developments in direct thermochemical liquefaction of biomass: 1983-1990

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