T.P. 3376

SOME PROP~RTI~S OF MIXED PARAFFINIC AND OLEFINIC HYDRATES

H. H. REAMER, F. T. SELLECK AND B. H. SAGE, MEMBER AIME, CALIFORNIA INSTITUTE OF TECHNOLOGY,

PASADENA, CALIF.

ABSTRACT

An experimental investigation was made of the effect of temperature upon the three·phaEe pressure associated with the propane-water and propene-water systems when hydrates were present. In addition, the characteristics of the propane-propene­water system were established over a limited range of tem­peratures under conditions such that hydrate was formed. The hydrate phase for this system may be a solid solution and the distribution of propane and propene in it is similar to that found in the coexisting hydrocarbon liquid phase.

INTRODUCTION

A knowledge of the characteristics of hydrates of the hydro­carbons encountered in industrial practice is of importance in connection with the design of process equipment. Villard'" carried out early studies of hydrates, and de Forcrand" con­sidered the more probable compositions of the hydrates of hydrocarbons. Hammerschmidt' presented information about the propane-water and the isobutane-water systems. Scheffer' studied the hydrate of hydrogen sulfide in detail, and de For­crand reported on the hydrates of krypton, argon, and xenon.u

Roberts and co-workers'" determined the nature of the hydrates formed in the methane-water and ethane-water sys­tems. Carson and Katz'· studied the methane-propane-water, methane-pentane-water, and the methane-hexane-water systems in the four-phase region. The results of this rather extensive investigation indicated that the paraffinic hydrates formed solid solutions. The experimental evidence now available does not support the existence of hydrates of the pentanes-and­heavier hydrocarbons but it cannot be stated with certainty that such hydrates are not formed. Stackelbergl1

,l!,13 made ex· tensive studies of the crystal structure of paraffinic hydrate, by means of x-ray techniques and found that hydrates posses, a definite structure and composition. The existence of such a structure does not preclude the formation of solid solutions of hydrates in aqueous systems containing two or more hydro­carbons.

Wilcox, Carson and Katz" reviewed the information on the hydrates of importance in the processing of natural gas and presented data concerning their formation from natural gas. Kobayashi and Katz'" made studies at high pressure of the hydrate of methane, and Unruh and Katz'" investigated hy­drates in mixtures of carbon dioxide and methane.

Frost and Deaton"''"''!>''·'" contributed to the knowledge of the composition of the paraffinic hydrates. The irregularities in the experimental results were several times the expected uncertainties. This 'experience confirms the behavior encoun­tered by other investigators indicating that hydrates tend to occlude water during their formation, thus rendering difficult the direct measurement of their composition. Miller and

lReferences given at end of paper. Manuscript received in the Petroleum Branch office March 31, 1952. For material supplementary to this article order Document 3€09 from

American Documentation Institute, 1719 N Street N,W" Washington 6, D. C., remitting $1.00 for microfilm (images one in. hhrh on standard 35 mm motion picture film) 01' $1.00 for phDtocopie:; ("ix by eight in.) readable without optical aid.

Strong" investigated a numb~r of paraffinic hydrates from the standpoint of their possible application to the industrial storage of gas. Powell" studied the effect of solutes upon the decomposition temperature of paraffin hydrates. Marked low­ering of the decomposition temperature at a given pressure may be obtained by the use of such additive agents as ethylene glycol, urea, and sodium chloride.

APPARATUS AND METHODS

Two methods were here employed to study the behavior of hydrates. The first involved a glass capillary within which the hydrocarbons and water were confined over mercury. The second made use of a double-ended weighing bomb technique." The glass capillary equipment has been described elsewhere." A schematic drawing of it is presented in Fig. 1, where the arrangement of the agitator and mercury reservoir is shown in some detail. The lower part of the glass capillary, D, was enlarged to afford space within which the fluids used in the investigation could be stored at low pressures after their introduction through the valve, C. The temperature of the capillary was controlled by the circulation of a hydrocarbon oil of low viscosity from the agitated bath, B, through the vacuum jacketed column, C. The pump, A, was employed for the circulation of this oil. A relatively clear view of the capil­lary tube, D, was obtained through the vacuum jacket. Mer­cury was introduced into the lower part of the vessel, E, from

G

c

D

FIG. 1 - SCHEMATIC VIEW OF ARRANGEMENT OF GLASS CAPILLARY.

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T.P. 3376 SOME PROPERTIES OF MIXED PARAFFINIC AND OlEFINIC HYDRATES

AIR

A

TO PRESSURE BALANCE I

AGITATING J DEVICE

, I , , , , C ' l- ______ .l

KEROSENE BATH

I---!><r---t'-F_V_A-I>C~U_UM 5 Y STEM

TRAP Me LEOD GAGE

WEIGHING BOMB

FIG. 2 - ARRANGEMENT OF EQUILIBRIUM BOMB EQUIPMENT.

the chamber, I, aofld the pressure within the system was deter· mined by means of the balance, H." The latter instrument was used in conjunction with the steel U·tube, J, which was arranged so as to permit elevation control of the mercury-oil interface in one of the arms of the U-tube_ The uncertainty in the measurement of pressure was estimated to be 0.2 psi or 0.1 per cent, whichever was larger_ Agitation within the capillary was provided by means of a stainless steel spiral, K, which was driven by the shaft, L, through the packing gland, M. The glass capillary was introduced into the vessel, E, through the packing gland, F.

The temperatures of the observations were determined by means of copper-constantan thermocouples used in conjunction with a double potentiometer of the White type having a range of 10,000 microvolts. The thermocouples were calibrated by means of a strain-free platinum resistance thermometer, the characteristics of which had been established by the National Bureau of Standards. The temperature of the exterior surface of the capillary tube was known within 0.2°F relative to the international platinum scale. The total effective volume of the capillary was determined from the elevation of the mercury interface relative to the closed end of the tube, which had been previously calibrated by weighing quantities of mercury withdrawn from the filled tube_ The total volume of the system was believed known within one per cent except in the con­densed regions when the volumes were so small that the uncer­tainties may have been as large as three per cent. The eleva­tion of the mercury interface relative to the closed end of the glass capillary was determined by means of a cathetometer.

The desired amounts of the hydrocarbons to be investigated were introduced gravimetrically as has been described." The quantity was checked by volumetric measurements under con­ditions at which the specific volumes of the hydrocarbons in question were known." The proper quantity of water was then added and the amount established from the change in the total volume of the system. A small uncertainty resulted from the mutual solubility of water and the hydrocarbons. Appropriate corrections were made for such solubilities and uncertainties greater than one per cent were not experienced in determin­ing the quantity of water and hydrocarbon employed.

The temperature then was reduced below that at which hydrates were formed. It was subsequently brought to the value chosen for the investigation of the isothermal change in total volume with pressure. The phenomenon of partial melt­ing and the decomposition of the last trace of the hydrate phase were followed in some detail by such isothermal investi. gations. Similar studies were made under isobaric conditions. However, it was found that as a result of the longer time

required to obtain thermal equilibrium, the isobaric studies were much less effective than those made at a constant tem­perature. The majority of the results presented here have been obtained from isothermal investigations.

The equipment employed to determine the composition of the coexisting phases in the propane-propene-water system is shown schematically in Fig. 2. It involved the equilibrium bomb, B; the agitator, H; a means of introducing or with­drawing mercury from the vessel, A; and a sample withdrawal system shown at D, E, and F. A photograph of the double­ended equilibrium vessel used in these investigations is pre­sented in Fig. 3. The details of the design of this equipment are already available." Desired quantii'es of hydrocarbons and water were introduced into the equTbrium bomb, B, of Fig. 2 and the whole was brought to temperature equilibrium. Agitation was accomplished by oscillation of the equilibrium vessel about an axis symmetrical with and normal to it. After hydrate had been formed, the pressure was raised by the introduction of mercury from the chamber, A, and agitation continued until there was no further change in pressure with time at a constant temperature. The pressure and temperature measurements were carried out in a similar manner and were of cQmparable accuracy to those described for the glass capil­lary equipment.

After equilibrium had been obtained, the liquid phases were displaced from the equilibrium vessel, B, by further introduction of mercury, the temperature and pressure within being held constant. A small internal filter was located in one end of the bomb, B, to prevent removal of the hydrates. After the liquid phases had been displaced from the equipment, the mercury was withdrawn in part and the temperature was raised sufficiently to decompose the hydrates. The displaced hydrocarbons were dried and the gain in weight of the drier, E, was considered to be the water associated with the hydro­carbons. The change in weight of the weighing bomb or of the gas sampling bulb was treated as hydrocarbon. The exceS3 mercury displaced through the vessel, B, of Fig. 2, was col­lected in the trap, D. After displacement this trap was weighed, evacuated, and reweighed. Any loss in weight was considered to result from the presence of water and this weight was added to that collected in the drier, E.

After the hydrate had been decomposed, mercury was again introduced into the vessel, B, from A and the hydrocarboni and water were collected in the gas sampling bulb attached at F, and the drier, E, respectively. These procedures per­mitted the total quantity of hydrocarbons and of water to be accounted for with an uncertainty of not more than one per cent. The distribution of the propane and propene in the hydrocarbons withdrawn was determined by catalytic hydro.

FIG. 3 - PHOTOGRAPH OF EQUILIBRIUM BOMB.

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H. H. REAMER, F. T. SElLECK AND B. H. SAGE T.P. 3376

1000

a z

w 500 a: c( ::> o VI

a: w a. 200

VI o z ::> ~

w a: ::>

100

~ 50 w a: a.

20

HYDRATE AND

AQUEOUS f- LIQUID

r

HYDROCARBON LIQUID I)- AND AQUEOUS LIQUID

)-

1-<

1-<

~ ~ ---y-

/

fi GAS AND AQUEOUS LIQUID

o AUTHORS

? DEATON AND FROST -0- WILCOX, CARSON,

AND KATZ I

40 60 TEMPERATURE of

FIG. 4 - LOCUS OF THREE·PHASE STATES FOR PROPANE·WATER SYSTEM.

'00

.00

300 HYDROCARBON LIQUID

AND HYDRATE

200 AND AQUEOUS LIQUID

... AQUEOUS co <

LIQUID !

g ~ "-100 .. .. -'

... II: :> ::! f eo

.0

GAS AND ·40

AQUEOUS LIQUID

30

FIG. 5 - LOCUS OF THREE·PHASE STATES FOR PROPENE·WATER SYSTEM.

Table I - Three-Phase States for Propane-Water System

Pressure, psia

296.8 214.2 99.2 60.0 44.2 34.9

Tempera-ture, 'F Phases Present

42.1 Hydrate, aqueous liquid, and hydrocarbon liquid 41.9 Hydrate, aqueous liquid, and hydrocarbon liquid 41.8 Hydrate, aqueous liquid, and hydrocarbon liquid 39.3 Hydrate, aqueous liquid, and gas 36.6 Hydrate, aqueous liquid, and gas 34.1 Hydrate, aqueous liquid, and ps

Table II - Three-Phase States for Propene-Water System

------------------ ._------_.-Pressure, Tempera-

psia ture. OF Phases Present

74.9 32.9 Hydrate, aqueous liquid, and gas 78.6 33.4 Hydrate, aqueous liquid, and gas 88.5 34.1 Hydrate, aqueous liquid, and gas 98.6 41.0 Gas, aqueous liquid, and hydrocarbon liquid

100.9 39.6 Gas, aqueous liquid, and hydrocarbon liquid 129.0 57.4 Gas, aqueous liquid, and hydrocarbon liquid 132.6 59.4 Gas, aqueous liquid, and hydrocarbon liquid 159.8 73.4 Gas, aqueous liquid, and hydrocarbon liquid 98.2 34.5 Hydrate, aqueous liquid, and hydrocarbon liquid

207.7 34.9 Hydrate, aqueous liquid, and hydrocarbon liquid 308.3 35.2 Hydrate, aqueous liquid, and hydrocarbon liquid

Table III - Three-Phase States* for Ethane-Water System

Pressure, psia

141.0 241.7 308.8 478.4

Isobaric Measurements

Temperature, 'F

44.1 49.4 52.7 57.6

*Hydraie, gas. and aqueous liquid

Table IV - Three-Phase States'::' for Ethene-Water System

Pressure, Tempera- Pressure. Tempera-psia ture, OF psia tUl'e, of

Isobaric Measurements 143.6 34.7 322.2 47.4 168.3 41.4 349.5 49.3 179.9 41.3 362.6 49.5 203.6 42.0 385.7 51.0 257.3 43.0 427.7 50.5 280.9 45.1 454.0 52.7 302.4 43.7 474.9 53.7

513.3 55.3 Isothermal Measurements

82.2 29.9 258.6 46.3 91.0 32.0 302.6 47.9 99.3 34.6 335.3 50.4

127.0 39.0 402.3 52.6 171.5 41.3 440.2 54.7 226.4 43.7

*Gas, aqueous liquid, and hydrate

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T.P. 3376 SOME PROPERTIES OF MIXED PARAFFINIC AND OlEFINIC HYDRATES

1000

800

600

vi 400

HYDRATE AND III «

300 AQUEOUS SOLID

z

ci <f>

200 a: u "-

.n III HYDRATE AND ..J

'" AQUEOUS GAS AND

" 100 AQUEOUS LIQUID if> if> W 80 a: "-

60 ® AUTHORS

GAS AND o ROBERTS ET Al

40 AQUEOUS SOLID

60

TEMPERATURE or

FIG. 6 - LOCUS OF THREE-PHASE STATES FOR ETHANE·WATER SYSTEM.

genation of the unsaturated hydrocarbons." The relative quan· tity of propane and propene was established within 0.003 mole fraction.

MATERIALS

The ethane used in these studies was obtained from the Carbide and Carbon Chemicals Corp. and was purified hj repeated fractionation in a glass column packed with small helices. The purified material contained enough impurities t~) yield approximately two lb change in vapor pressure at 70°F as a result of a change in quality from 0.2 to 0.9. The ethane was prepared by catalytic dehydration of purified ethyl alcohol by contact with aluminum oxide at approximately 840°F and atmospheric pressure. The crude ethene was purified by frac· tionation in the same column used for the purification of ethane. The refined material showed less than 0.6 psi change in pressure from dew point to bubble point. These samples were stored in stainless steel weighing bombs before use.

The propane and propene were obtained from the Phillip, Petroleum Co. An analysis submitted by the company ind·· ,'ated that the propane contained less than one per cent of impurities. However, the olefin sample may have had as much as one per cent of material other than propene. The propene was purified by fractionation in the column previously de· scribed and was believed to contain not more than 0.002 mole fraction material other than propene. It was found that the decomposition temperatures for propene hydrate prepared from the crude and from the purified propene agreed witbin O.I°F.

The water employed was obtained from laboratory distilled stocks which were fractionated once before lEe in order to remove dissolved gases.

EXPERIMENTAL RESULTS

The experimental results for the propane· water and the propene-water systems at three·phase states are recorded i:1 Tables I and II and in Fig~. 4 and 5. The data of Deaton and

Fros!'O and Wilcox, Carson and Katz" have been included ill Fig. 4. The present measurements for the propane-water sys· tern are in good agreement with those of the other investiga· tors. The four-phase pressure of the propene-water system was approximately 10 psi higher and occurred at a tempera· ture 7°F lower than the propane-water system.

Information concerning the ethane-water and ethene-water systems is·. recorded in Tables III and IV respectively. The data have been segregated into isobaric and isothermal meas· urements as was described earlier. The data of Roberts, Brownscombe and Howe' have been included in Fig. 6 along with the present data for the ethane-water system. Two four­phase states are presented in this diagram. No experimental data are available for the three·phase equilibrium involving hydrate, ice, and aqueous liquid or for the three-phase equi . librium involving gas, ice, and aqueous liquid; however, these latter states may be established with but small uncertainty from the behavior of water. The results of the investigation of the ethene-water system under isothermal conditions are presented in Fig. 7. These data represent the three·phase equilibria involving gas, hydrate, and aqueous liquid. The measurements made at constant pressure with a change in temperature gave slightly lower values of the decomposition temperature of the hydrate than were obtained from the studies involving a change in pressure at constant temperature.

A limited series of measurements was made of the propane­propene-water system. In these studies the ratio of the mole fraction of propane to propene was maintained at a fixed value as has been done for other ternary systems.'''·'' In this instance the composition parameter C may be defined in the following way:

n, X3 (1) C=---

In this equation n is the mole fraction in the system and X the mole fraction in the liquid phase whereas the subscript i 3 and III refer. respectively, to propane and propene. The

I U Z

w a: « :;, (J Vl

a: w a. Vl

~ :;,

2 w a: :;, ~ w 2:

1000r---------,----------.--------~

500r---------+---------+-------~ HYDRATE AND AQUEOUS LIQUID

200r---------+-------~+-------~

GAS AND AQUEOUS LIQUID

100 I---------.'! I------+-----~ o

50~--------~--------~--------~ 35 45

TEMPERATURE Of

FIG. 7 - LOCUS OF THREE·PHASE STATES INVOLVING HYDRATE, GAS, AND AQUEOUS LIQUID FOR ETHENE-WATER SYSTEM.

200 PETROlEUM TRANSACTIONS, AIME Vol. 195, 1952

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H. H. REAMER, F. T. SELLECK AND B. H. SAGE T.P. 3376

experimental techniques were similar to those used in the propane-water and the propene-water systems. The hydrate was made up of translucent crystals which became substan­tially transparent upon partial melting. The experimental work indicated that the mixed hydrates decomposed over a range of temperatures at a given pressure. The first traces of hydrate decomposition under isobaric conditions occurred at a temperature between that corresponding to the decompo­sition of pure propane hydrate and of pure propene hydrate. In Table V are reported corresponding values of pressure and temperature at which hydrate initially decomposed for two different mixtures of the restricted ternary system. A'i indicated by the phase rule for a three-component system, a three-phase locus possesses two degrees of freedom and the four-phase state is univariant.

The behavior of the two mixtures investigated is shown graphically in Fig. 8. At a given pressure the temperature at which the hydrate begins to melt is a function of the parameter C. Such behavior appears to occur both for the ternary equilibrium involving hydrate, aqueous liquid, and hydrocarbon liquid and for the equilibrium including hydrate, aqueous liquid, and gas. The mixtures behave essentially as binary two-phase systems because of the very limited solubility of hydrocarbon in the aqueous phase and the small amount of water present in the gas phase. From the smoothed dat:~ for the equilibrium behavior of hydrate, aqueous liquid, and gas, together with the assumption of no intersolubility of the

Table V-Three-Phase States for a Restricted Propane­Propene-Water System

Pressure, Tempera-psia ture. OF Phases Present

-------C~=~0~.5~2~4~6------------

43.6 51.3 53.7 53.8 57.7 62.8 65.4 66.5 72.4 72.7 72.8 73.2 88.7 90.3 93.2

105.5 120.6 138.3 98.3

116.7 126.9 137.8 183.2 264.4 277.0 288.2 396.8

57.1 64.6 72.1 74.9 77.5 94.0

113.3 131.9 107.5 194.9 278.3

33.0 34.3 34.1 34.2 34.6 35.6 35.3 35.3 37.4 37.0 36.4 37.3 39.2 41.3 45.5 52.3 59.5 71.2 38.3 38.3 38.3 38.4 38.4 38.8 38.8 38.8 38.9

33.2 34.4 35.4 35.6 35.7 41.7 53.6 63.9 36.9 37.0 37.1

Hydrate, aqueous liquid, and gas Hydrate, aqueous liquid, and gas Hydrate, aqueous liquid, and gas Hydrate, aqueous liquid, and gas Hydrate, aqueous liquid, and gas Hydrate, aqueous liquid, and gas Hydrate, aqueous liquid, and gas Hydrate, aqueous liquid, and gas Hydrate, aqueous liquid, and gas Hydrate, aqueous liquid, and gas Hydrate, aqueous liquid, and gas Hydrate, aqueous liquid, and glS Aqueous liquid, hydrocarbon liquid, and gas Aqueous liquid, hydrocarbon liquid, and gas Aqueous liquid, hydrocarbon liquid, and gas Aqueous liquid, hydrocarbon liquid, and g1S Aqueous liquid, hydrocarbon liquid, and gas Aqueous liquid, hydrocarbon liquid, and g"S Aqueous liquid, hydrocarbon liquid, and hydrate Aqueous liquid, hydrocarbon liquid, and hydrate Aqueous liquid, hydrocarbon liquid, and hydra'e Aqueous liquid, hydrocarbon liquid, and hydrat~ Aqueous' liquid, hydrocarbon liquid, and hydrate Aqueous liquid, hydrocarbon liquid, and hydrate Aqueous Jiquid, hydrocarbon liquid, and hydrate Aqueous liquid, hydrocarbon liquid, and hydrate Aqueous liquid, hydrocarbon liquid, and hydrate

C = 0.3148 Hydrate, aqueous liquid, and gas Hydrate, aqueous liquid, and gas Hydrate, aqueous liquid, and g1S Hydrate, aqueous liquid, and gas Hydrate, aqueous liquid, and gas Aqueous liquid, hydrocarbon liquid, and gas Aqueous liquid, hydrocarbon liquid, and gas Aqueous liquid, hydrocarbon liquid, and gas Aqueous liquid, hydrocarbon liquid, and hydrate Aqueous liquid, hydrocarbon liquid, and hydrate Aqueous liquid, hydrocarbon liquid. and hydrate

Table VI - Comparison of Experimental and Calcu­lated Three-Phase Pressures for the Propane-Propene­

Water System

Composition a PreS6ureb Pressureb

Parameter C Experimental Calculated

0.3148 0.3711 0.5246 0.7589

92.0 91.4 88.3 84.3

40°F 92.0 91.1 88.5 84.2

Experimental Calculated

145.6 144.2 140.3 133.7

70°F 145.8 144.5 140.8 133.9

"Defined in Equation (1). hPresBures expressed as psia.

water and hydrocarbons in liquid phases and of an ideal solu­tion in the gas phase, it is possible to compute the correspond­ing values of equilibrium pressure and temperature for chosen values of the parameter C. By utilizing recently available data" such calculations were made for temperatures of 40° and 70 9 F and were used as the basis for the series of curves in that temperature range in Fig. 8. It appears from the correspondence between the experimental points and the curves and from the comparison shown in Table VI that the behavior of the propane-propene-water system at low pres­sures and temperatures may be predicted with reasonable accuracy as long as hydrate is not formed.

By means of the weighing bomb techniques which have been described earlier in this discussion 14 measurements were made to determine the composition of the coexisting hydro­carbon and hydrate phases in the three-phase equilibria in-

I U Z

w a: « :::> o III

a: w 0..

III o z :::> o 0..

w a: :::> III

~ g:

1000~---------.---------,----------,

500~------~~---------r--------~

HYDRATE AND

200 AQUEOUS LIQUID

HYDROCARBON LIQUID

AND AQUEOUS LIQUID

50 I------H-"~T GAS AND AQUEOUS LIQUID

20L---------4LO--------~6~0--------~

TEMPERATURE Of

FIG. 8 - PRESSURE-TEMPERATURE DIAGRAM fOR RIi~TRJCT~D MIXTURES FOR PROPANE, PROPENE, AND WATER.

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T.P. 3376 SOME PROPERTIES OF MIXED PARAFFINIC AND OLEFINIC HYDRATES

4-o

w a:

44 .-------.-------,-------,--------,------,

AQUEOUS LIQUID AND HYDROCARBON LIQUID

40 ~------~------~------~~~~r-----~

~ AQUEOUS LIQUID, ~ HYDROCARBON LIQUID, ~ 36 ~~~~~~-----+------_A~N~D-LHUY~D~R~A~T~E----__1 ::!: w I- AQUEOUS LIQUID

AND HYDRATE

0.2

MOLE

0.4 0.6 0.8

FRACTION PROPENE

FIG. 9 - PRESSURE·TEMPERATURE DIAGRAM FOR RESTRICTED PROPANE· PROPENE SYSTEM AT 400 PSI.

volving hydrate. The results of these measurements are avail· able elsewhere.'· All measurements were made at a pressure of 400 psi and at temperatures between 32° and 39°F. The values of the equilibrium ratios for the components in the hydrocarbon liquid and hydrate phases were near unity. It was necessary to carry out a relatively large number of meas­urements in order to make sure that the results obtained were trustworthy. The standard deviation of five measurements for which complete data were obtained was 0.011. One measure­ment was discarded because of an excessive deviation, and no hydrate was formed in the remaining eight measurements. It appears that the hydrates may form a solid solution. The composition of the solid hydrate phase or phases follows closely that of the coexisting hydrocarbon liquid phase.

By combining the data obtained from the direct measure­ments of the composition of the coexisting phases and those shown in Fig. 8, it is possible to construct a temperature­composition diagram for the hydrocarbon phases. It should be realized that this diagram corresponds to a restricted ter­nary system in which there exists an excess of the aqueous liquid at all compositions. Fig. 9 is such a temperature-com­position diagram for a pressure of 400 psi. Data regarding the compositions of the coexisting phases were employed to aid in establishing the aqueous liquid, hydrocarbon-liquid boundary curves and they involve somewhat more uncertainty than does the aqueous liquid-hydrate boundary which also is presented in Fig. 9

ACKNOWLEDGMENT This program of investigation was made possible by support

from the Texaco Development Corp. Virginia Berry and Olga Strandvold aided in the assembly of the data and in the preparation of the manuscript, which was reviewed by W. N. Lacey.

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8. Roberts, O. 1., Brownscombe, E. R., and Howe, L. S.: "Constitution Diagrams and Compositions of Methane and Ethane Hydrates," Oil and Gas Jour., (1940) 391, 30.

9. Roberts, O. 1., Brownscombe, E. R., Howe, 1. S., and Ram­ser, H.: "Phase Diagrams of Methane and Ethane Hy­drates," Petro Eng., (1941) 12, [6] 56 ..

10. Carson, D. R, and Katz, D. 1.: "Natural Gas Hydrates," Trans. AIME, (1942) 146, 150.

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13. von Stackelberg, M.: "Feste Gashydrate," Naturwiss., (1949) 36, No. 12, 359.

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15. Kobayashi, R., and Katz, D. 1.: "Methane Hydrate at High Pressure," Trans. AIME, (1949) 186, 66.

16. Unruh, C. H., and Katz, D. 1.: "Gas Hydrates of Carbon Dioxide-Methane Mixtures," Trans. AIME, (1949) 186,83.

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18. Deaton, W. M., and Frost, E. M., Jr.: "Gas Hydrates in Natural Gas Pipe Lines," Amer. Gas Assoc. Monthly, (1937) 19,219; Oil and Gas Jour., (1937) 36,75; Amer. Gas Jour., (1937) 146, 17; Gas Age, (1937) 80, 37.

19. Deaton, W. M., and Frost, E. M., Jr.: "Gas Hydrates," Proc. Amer. Gas Assoc., (1938) 112.

20. Deaton, W. M., and Frost, E. M., Jr.: "Gas Hydrates and Their Relation to the Operation of Natural-Gas Pipe Lines," Bureau of Mines MonOgraph, (1946) 8.

21. Deaton, W. M., and Frost, E. M., Jr.: "Gas Hydrates," Gas Age, (1938) 81, [11] 33.

22. Miller, B., and Strong, E. R., Jr.: "Hydrate Storage of Nat~ral Gas," Amer. Gas Assoc. Monthly, (1946) 28, 63.

23. Powell, J. S., Jr.: "Lowering Decomposition Temperature of Natural Gas Hydrates by Solutes in Aqueous Solutions," Proc. Pacific Gas Assoc., (1939) 30, 52; Gas, (1939) 15, 39.

24. Sage, B. H., and Lacey, W. N.: "Apparatus for Study of PressureN olume-Temperature Relations of Liquids and Gases," Trans. AIME, (1940) 136, 136.

25. Nysewander, C. N., Sage, B. H., and Lacey, W. N.: "Phase Equilibria in Hydrocarbon Systems. The Propane-n-Butane System in the Critical Region," Ind. and Eng. Chem., (1940) 32, 118.

26. Sage, R H., and Lacey, W. N.: Thermodynamic Properties of the Lighter Hydrocarbons and Nitrogen, API, New York, 1950.

27. McMillan, W. A., Cole, H. A., and Ritchie, A. V.: "Deter­mination of Ga'seous Olefins or Hydrogen by Catalytic Hydrogenation," Ind. and Eng. Chem. Anal. Ed., (1936) 8,105.

28. Carter, R. T., Sage, R H., and Lacey, W. N.: "Phase Be­havior in the Methane-Propane-n-Pentane System," Trans. AIME, (1941) 142,170.

29. McKay, R. A., Reamer, H. H., and Sage, R H.: "Volu­metric and Phase Behavior in the Propene-Propane Sys­tem," Ind. and Eng. Chem., (1951) 43, 1628.

30. Reamer, H. H., Selleck, F. T., and Sage, R H.: "Compo­~ition of the Coexisting Hydrocarbon and Hydrate Phases in the Propane-Propene-Water System," American Docu­mentation Institute. Washington, D. C., Document No. 3609, (1952). * * *

202 PETROLEUM TRANSACTIONS, AIME Vol. 195, 1952

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