INDUSTRIAL AND ENGINEERING CHEMISTRY
1140
RESULTS OF A PLANT RUN
The plant trial was run at the Midway, Ky., plant according to the procedure used in the first fermentations reported in this paper. Wheat-milo stillage was used, and two fermenters of the -5 and two of the Puerto Rico variety of sweet potatoes were set. The latter consisted almost entirely of the shredded form. There were two departuras from the initial specifications for the run, which were due to the low pH of the Midway plant stillage. It was not possible to put the specified amount of stillage by volume in the fermenters; therefore 6.0 to 10.0% was used. The cooking pH was between 5.00 and 5.40, although 5.30 to 5.60 was recommended. The bonded yield of the two fermenters of Puerto Rico was 4.77 and of the fermenters of G 4 5 waa 5.44 proof gallons per bushel. While these yields were not so high as might have been anticipated from the laboratory results, they were encouraging, especially since it had been necessary to depart from the stillage and pH specificationq Plant operations revealed mash pumping to be no problem, despite the deceptive appearance, this mash had the pumping characteristics of water. Therefore it is believed that fermenter concentrations of 32 to 35 gallons of mash per bushel are in line. These correspond to grain mash concentrations. Samples of sweet potato stillage were evaporated and dried on a laboratdry dryer. This material was analyzed for comparison with distillers’ dried solubles, a valuable poultry feed supplement. Comparative data (dry basis) follow: Distillers’ Dried Solublea (Corn) Protein. 5 Fat. % Ash 96 R i b h a v i n , y/qrani Pantothenic acid. s/pram
30
10-12 6 15-20
26-30
These data indicate potential value as a poultry feed supplement. The protein is low for dairy cattle feed. CONCLUSIONS
Dehydrated sweet potatoes may be cooked and Gonverted under conditions similar to those employed in grain processing. It is evident that less severe cooking conditions are required for sweet potato starch than for cornstarch. Dehydrated shredded sweet potatoes will yield up to 15-20% more alcohol per bushel than can be obtained from high-grade corn. Samples of the G 4 5 variety studied are superior to those of the Puerto Rican variety, on the basis of laboratory and plant alcohol yields. Dehydrated sweet potatoes need not be ground before cooking although milling does increase the alcohol yield slightly. Further research, now in progress, is necessary to obtain the maximum alcohol yield from dehydrated sweet potatoes. The by-product credit picture has been only partially studied, but it is apparent that the by-product may not be equivalent in value to grain alcohol by-products. The dried grains yield per bushel is little more than half that obtained from grain processing, and the protein content is 16% as compared with 30% in corn by-products. LITERATURE CITED (1)
Kimbrough, W. D., La. State Univ., Agr. Expt. Sta., La. RILZI. 348 (1942).
16.4 4.8
(2) Kolachov, Paul, Chemurgic Digest, 3, 24 (1944). (3) Stark, W. H., Adams, S. L., Scalf, R..E.,and Kolachov, Paul, IND. ENG.C ~ E MANAL. ., ED.,15, 443 (1943). (4) U. S. Dept. of Agr., Agricultural Statistics (1940). (5) Williamson,E’. S., La. State Univ., Agr. Expt. Sta., Circ. 25 (1942).
16:3 38.9
PRESENTED before the Division of Agriou!tural and Food Chemistry at the 108th Meeting of the A\rm~rc%v C H F x I c A L S o c r e ~ rNew , York, N. Y.
Sweet Potato Soluble8
PETROLEUM COKE Formation and Properties
T
Vol. 36, No. 12
H E trend of modern cracking processes is towards the use of distillate charging stocks rather than residues. This raises the problem of disposing of heavy residues, both straight-run and cracked. There are two general methods by which such residues may be converted into salable products; one is the addition of hydrogen, the other is the removal of carbon. The hydrogenation of heavy residues is a costly process which has not yet earned genuine profits in peacetime. Coking, on the other hand, is already a well-established refinery operrttion. Hence it appears that, in the immediate postwar period a t any rate, the economic importance of coking processes in the petroleum industry will increase, and larger quantities of petroleum coke will come into the market. Compared with other solid fuels, petroleum coke has received relatively little study. Descriptions have been published of various coking processes and plants, but the emphasis has usually been on the distillates. Mekler (,%‘O), Morrell and Egloff (88), Stroud (86),and others have given typical analyses of cokes from various sources. hlorrell and Egloff also give information on shatter strength, true density, cellular space, and the relative effect of various solvents.
A. G. V. BERRY AND R. EDGEWORTH- JOHNSTONE Trinidad Leaseholds Ltd., Pointe-a-Pierre, Trinidad, B. W. I.
The common meaning of the term “coke” is a cellular residue obtained by the pyrolysis of coal. I n the petroleum industry the word denotes a product similarly derived from oil. Chemists describe as coke any compact carbonaceous residue obtained by the destructive distillation of organic compounds. For the purposes of this paper, coke will be defined as a solid infusible residue obtained by the pyrolysis of organic compounds under conditions such that the residue passes through a plastic st age before becoming infusible. Coke in this sense can be prepared from a wide range of organic materials. The macrostructure of a coke does not depend upon the structure of the parent material, which is destroyed during the plastic stage, but upon the conditions under which pyrolysis is effected. It was formerly believed that coke consisted largely of “amorphous carbon” which was considered to be a separate allotrope. However, x-ray analysis has failed to reveal any such allotrope. On the contrary, it has shown that all forms of “amorphous” carbon, including carbon black, give interference figures similar to those of graphite (8, 3, 6,8-16, 84, 88). Cathode-ray diffraction studies ( d l ) , chemical tests (84), and observations with the electron microscope ( 1 1 ) combine to support the view that coke
December, 1944
1141
INDUSTRIAL AND ENGINEERING CHEMISTRY
Petroleum coke is essentially a disperse system composed of graphite-like crystallites embedded in an organic matrix. Experiments on the coking of a cracked asphalt under different time-temperature conditions rrhow that the coking process can conveniently be regarded as taking place in four stages, correeponding to the production of pitch, semipitch, asphaltic coke, and carboid coke. The properties of theee substances are described, and their bearing on the quality and commercial value of petroleum coke is indicated.
consists of minute graphite crystallites surrounded by organic compounds of high molecular weight. Recent work by Riley and collaborators suggests that the crystallitea may consist, not of true graphite, but of "mesomorphous" transition states between the parent compound and graphite. X-ray photographs are interpreted as revealing substances composed of hexagon lattice planes of carbon atoms spaced somewhat farther apart than in graphite and not oriented with respect to one another (7). The existence of a similar structure in carbon black has been reported (%I). The chemical reactions which form petroleum coke appear to consist in the conversion of nonaromatic portions of the original material to aromatics and the progressive condensation of the aromatic nuclei to a more complex structure. According to Tilicheyev (m), the cracking of paraffin hydrocarbons to coke may be represented by the following series:
Paraffins ----t olefins +aromatics with aide chains --.+
condensed ring systems +Bsphaltenes +carboids
The readiness with which a given hydrocarbon forms coke depends upon its position in this series. A study of the carbonization of cellulose has shown that the formation of hexagon lattice planes of carbon atoms is appreciable at temperatures 81) low as 400' c. (4). From a physical standpoint, therefore, it appears that all cokes, including petroleum coke, are essentially disperse systems composed of minute crystallites embedded in a matrix of highly condensed aromatic somgourids. The crystallites consist of either graphite or closely related substances. Such crystallites have been reported to exist even in Bsphalt (98). As carbonization proceeds, the crystallites grow at the expense of the matrix, which also loses volatile matter and changes in character. The hydrogen content of the system naturally decreases as the temperature rises (17). Above 1100' C. the hydrocarbon matrix has practically disappeared (S),but the crystallites continue to grow at higher temperatures (14), and conversion to massive graphite is not complete below about 2600" C. Petroleum coke thus forms part of a continuous series of disperse systems with asphalt a t one end and pure graphite at the other. It comprises those members of the series which, on the one hand, do not soften on heating and, on the other, are poor conductors of electricity compared with graphite. . The physical properties of a disperse system depend chiefly upon the properties of the continuous phase or matrix. I n petroleum coke the matrix is an infusible solid substance in which two main t y p of constituent may be recognized: asphaltenes, which are soluble in trichloroethylene, and carboida, which are not. On being heated, asphaltene~decompose inta carboids and volatile matter without fusion (I). Asphalt, on the other hand, contains asphaltic resins, oily constituenta, and asphaltenes (f.9, M),and these form s matrix which fuses well below the temperature at which it begin8 to decompose. The essential differenre between petroleum coke and asphalt is that the former incremes in carboid content by pyrolysis without melting, whereas the latter always passes through the molten stage before the.carboids are formed.
Products formed at temperatures above 1100" C. contain practically no matrix material, and their properties are determined chiefly by the size of the crystallites (9, 11). However, such products are outside the range of normal petroleum cokes. COKING EXPERIMENTS
The following experiments were designed to throw light on rertain practical problems connected with the production and utiliqtion of petroleum coke. The main points of interest were the general mechanism of the coking process and the relation between some properties of the cokes produced. No great refinement was attempted in the coking procedure, since it WBB not to beanticipated that laboratory results would be quantitatively reproducible on a large scale. I n particular, the temperature distribution throughout the charge was not studied. Nevertheless, the results ehow rertain definite trends. The starting material was an asphalt obtsined by vacuum distillation of residuum from the thermal cracking of reduced crude. This asphalt had the following properties: MoLsture Or anic volatile matter, % Aaf % Fir& carbon, % Sulfur, % Softening oint ring and ball),
Trace
O
Solubihty tricklorwthylene, % Bulk deniity Friability number
45.0 0.2 54.8 1.8 125 99.8 0.6S8
C.
86.5
The bulk denRity was d c u l a t e d from the weight of 10 cc. of 10-20 mesh material packed down by tapping the container. The friability teat was designed to afford a comparative measure of the friability of small samples insufficient for the standard tumbler test. Ten cubic centimeters of 10-20 mesh material
TABLIP I.
SUMMARY OF MSWLTS AT E -
id, Charge, voiatile carbon, C. matter. % %
Aeb,
%
mMPEBA'PWES
C
% .
no.-
demity
97.9 94.8 88.0 66.7 7.5 1.7
87.0 86.3 80.0 71.4 23.4 7.6 2.8
0.611 0.617 0.666 0.670 0.648 0.628 0.654
89.0 77.8 89.3 53.5 37.0 5.6
87.8 89.7 41.0 87.5 18.1 8.2 2.2
0.639 0 . m 0.730 0.698 0.631 0.688 0.649
70.4 4.2
0.648 0.571 0.585 0.619 0.670 0.673 0.706
Initial Furnace Temperature 450' C. 15 30 45 80 120 240 360
420 416 424 437 468 458 470
42.7 40.8 84.2 82.0 10.1 11.8 7.4
56.8 59.3
41.4 86.0 29.7 28.0 15.2 7.4 6.4
58.2 68.7 69.6 71.8 84.8 91.8 94.2
0.5
65.5
67.6 88.9 87.4 91.7
0.4 0.3 0.4
0.6
0.8 0.9
Trace Initid Furnace Temperature BOO0 C. 0.3 0.8 0.7 0.2
0.5
0.8 0.4
Trace
Initial Furnace Temperature 800° C. 15 30 46 60
90 120 180
462 576 646 704 751 758 800
20.0 8.S 5.7
5.1
3.6 4.4 2.8
79.4 89.6 91.6 93.1 94.6 9a.n 95.2
0.6 1.9 2.7 1.8 1.8 2.1 2.0
42.5 8.3 4.4 3.s 1.2 0.8 0.4
5.5
4.5 2.8 2.8 2.1
TAB^ 11. ULTIMATE ANALYSES OF R E S I D w S OBTAINED INITIAL FURNAC~D TEMPERATUBE OF 800" C, Analysis, % by Weight 0 & N (X) H 8 by difference
Min. 0 15
ao
46 60 90 ,120 180
84.8 86.3 86.0 86.0 91.4 9a.2 93.8
95.0
6.2 4.8 3 7 3.6 3 4 3.0 1.9 1.3
1.77 1.86 1.54 1.66 1.48 1.48 1.46 1.8U
7.7 7.0 8.7 8.9 3.7 2.4 8.8 1.4
AT
Empirical Formula CIWHIISO.~IXI.I CiooHtr8e.nX1.1 CIHH~B~.I~XI.I CIooHdr.oXr.r Ct~Hu80.soXt.t CiwHt&~~Xs.i c1uIIuB1.1,Xr.r DlroHi&.nXa.r
Vol. 36, No. 12
INDUSTRIAL AND ENGINEERING CHEMISTRY
1142
400
600 MAX.
700
TEMP. OF CHARGE %.
Figure 1. Effect of Maximum Temperature Attained
are weighed and transferred to a 20-mesh gauze cylinder 3.3 cm. in diameter and 14 cm. long, containing a loose steel rod 0.5 om. in diameter and 12.4 om. long. The cylinder is revolved horirontally for 500 revolutions at a rate of about 100 r.p.m. The weight of material p w i n g through the gauze cylinder, expressed a i percentage of the original material, is termed "friability
number". In carrying out a coking experiment, 300 grams of cracked asphalt were placed in an iron pot still, 3 inches in diameter and 11 inches in height (internal dimensions). A pyrometer well extended through the center of the lid to within 1.5 inches of the bottom of the still. The lid was also provided with a vapor outlet connected to a condenser and distillate receiver. The still was heated in an electric resistance furnace. The furnace was heated to a predetermined temperature, the still and charge were placed in the furnace, bnd the current was maintained a t the same value throughout the experiment. After distillation had begun, the temperature of the charge was recorded every 16 minutes. At a predetermined time after the first signa of distillation, the still and contents were removed from the furnace and allowed to cool. The residue was removed, weighed, and analyzed. Bulk density and friability number were determined as previously described. Organic volatile matter and ash were found by standard methods. Solubility in trichloroethylene was determined by extraction of 5 grams of powdered material in a Soxhlet apparatus. Twenty-one experiments were made at furnace temperatures of 450°, 600' and 800' C. The resulta are summarized in Table I. The residues obtained a t 800' C. were submitted to elementary analysis by the method of Dennstedt (6). The results, calculated on an ash-free basis, are shown in Table 11. The yields of products obtained from each experiment are shown in Table 111. To give an approximate idea of the character of the liquid products, the total distillates obtained from the later experiments a t each furnace temperature were combined to yield sufficient material for analysis. The results are presented in Table IV. DISCUSSION OF RESULTS
I n Figure 1 the volatile content of all the coke samples is plotted against maximum temperature attained in the center of the charge. Lowry and collaborators found that, in the case of coal, the properties of the coke were determined principally by the maximum temperature attained. The time a t that
temperature was relatively unimportant (16, 17, 18). This is not quite true of petroleum coke. There appears to be a tendency for material heated rapidly to its maximum temperature to give a coke of higher volatile content than that obtained when the same material is raised to the same temperature more slowly. This holds despite the fact that in the present experiments only the temperature a t the center of the charge was memured, so that the average temperature would have been higher in the more rapidly heated material. Evidently there is a general correspondence between maximum temperature and volatile content, but the time factor is by no means negligible. This is perhaps to be expected in view of the importance of time in the pyrolysis of liquid petroleum products. Figure 2 illustrates the relation between volatile content and solubility in trichloroethylene, bulk density, and friability number. These curves, taken in conjunction with the general appearance and physical characteristics of the residues, suggest that the coking process can be considered as occurring in four stages. The stages are demarcated by shaded bands to indicate that the transition from one stage to another is not sharply defined. It is convenient to give names to the types of residue which characterize the different stages; to avoid introducing new words, suitable names have been adapted from existing terminology-namely, pitch, semipitch, asphaltic coke, carboid coke. For the purpose of the present study these substances are defined in terms of their solubility in trichloroethylene and behavior OD heating:
STAGEI. The ori 'nal asphalt melts, then begins to decompose. SubstFntiZ proportions of carboids appear .in the li uid residue which increasw in density but retains Its fnability &en solid. The type of residue characteristic of stage I may
TABLE 111. YIELDSOF PRODUCTS Coking Period, Min. 15 30 45 60 120 240 360 15 30 45 60 120 240 a60
Distillate SP. gr. ' at 60 F.
%$?
Coke, % by Wt.
Undetd.,.
% by Wt.
Initial Furnace Temperature 460" C. 86 3 90 6 87 9 79 16 0 866 62 25 0.902 60 27 0.887 62 23 0.880
13 13 15
Initial Furnace Temperature 600° C. 96 4 87 11 o:ii1 78 13 0.880 78 13 0.856 70 20 0,866 68 20 0.873 65 21 0.874
2 9 9 10 12 14
... ... :
12 6 4 6
1
Initial Furnace Temperature 800' C. 22 26 0,945 30 17 0.951 33 12 0.966 32 14 80 0.966 20 30 0.970 90 30 22 0.965 120 0.963 8 180 a3 Includee water vapor, hydrocarbon gases and uncondenead vapors. and loaa. 16 30 46
TABLEIV. QUALITYOF DISTILLATESOBTAINEDAT EACH FURNACE TEMPERATURE Initial Furnace TemD.. O C. Organic volatile matter in coke, % Oil distillate Yield % by weight Sp. g;. at 60° F. Distillation of 100 cc. Initial boiling point, a. C. Diet up to 100a C % b vol. Diet' from 100-160' C by vol. D+: from 150-!200° C:: by vol. Dlst. from 200-250° C., by vol.
f
450 9.6
600 6.4
800 3.6
26 0.884
20 0.874
31 0.964
90 0.6 6.6 14.0 17.0
99 Trace 8.0 14.0
19.0
132 Nil 1.0 8.6 10.5
Docomber, 1961
INDUSTRIAL AND ENGINEERING CHEMISTRY
1143
conveniently be termed “pitch”. It is a fusible bituminous substance distinguished from asphalt by containing carboids (matter insoluble in trichloroethylene). STAGH~ 11. When the residue reaches a volatile content of 3044%, it begins to grow plastic and intumesce. Carboida suddenly increase in amount, bulk demity begins to diminish, and there is a shar fall in friability number. The residue which typifies stage 51 may be called “semipitch”. It is die ti uished from pitch by the ability to intumesce when heated w x o u t first melting to a liquid. STAW111. When the volatile content of the residue falls to 18-220/, intumescence ceases and the plastic masa hardens. Thereafter the residue becomes infusible and continues t o lose volatile matter without further change of shape other than shrinkage. Solubility in trichloroethylene decreases rapidly and bulk densit remains fair1 constant. The residue characteristic of sta e TI1 may be ca&d “asphaltic coke” from the fact that it stilf contains substantial proportions 01 as haltenea (matter soluble in trichloroethylene). It is a blact and somewhat friable substance, distinguished from semipitch by being infusible and not intumescing when heated. STAUE IV. When the volatile content reaches about 7% the residue has become practically insoluble in trichloroethylene. It changes in appearance and properties, becoming dark gray in color and much less friable. Its bulk density also begins to increme rapidly. The residue characteristic of stage IV may be termed “carboid coke”. It is distin ished from as haltic coke by containing substantially no aspfitenes, as wefi as by ita different appearance and greater mechanical strength. Logically the final stage or stages should cover the conversion of carboid coke to graphite, but this requires very high temperstures and is outside the scope of the present study. I n terms of the intermediate substances distinguished above, the coking process is represented by the following series:
Asphal+-+pitch+semipitch+asphaltic cokecarboid coke (4 graphite) This series may be regarded as a magnified picture of the final step in the series of Tilicheyev (27): “Asphaltenes+carboids”. The members of the above series are chemically obscure mixtures defined solely in terms of their macrophysical properties. These properties depend primarily upon the nature of the matrix in which a greater or lesser proportion of graphite or graphitelike substance is dispersed. An important factor is the relation between softening point and temperature of decomposition. When the softening point is below the decomposition temperature, the product is an asphalt or pitch. I n semipitch the softening point and decomposition temperature are of the same order. When the decomposition temperature is below the softening point, the product is asphaltic or carboid coke. Commercial petroleum coke is far from being a homogeneous product, and a batch of coke from a single operation will generally yield portions corresponding in properties to two or more of the substances distinguished above. These substances may therefore be regarded as the macro constituents of petroleum coke. They pass gradually from one to another, and there are no sharp boundaries such as occur between the macro constituents of coal. Nevertheless the physical properties and commercial utility of a given petroleum coke will depend upon the relative proportions in which the above constituents are present. These proportions, in turn, depend upon the conditions of coking. Coke from the chambers of cracking and external coking units consist chiefly of asphaltic coke, the volatile content of which varies according to the part of the chamber in which it is formed. Coke deposited near the vapor outlet may contain considerable proportions of semipitch and even pitch, especially from cracking units engaged on residuum operation. Asphaltic coke has the disadvantage that it is friable and dirty to handle and gives rise to an excessive proportion of fines. It will sometimes disintegrate to dust merely on prolonged exposure to weather. Asphaltic coke tends to be unsatisfactory for burning in lump form in industrial furnaces. Its strength is insufficient to
Figure 2. *Relationbetween Coke Properties
support a deep fuel bed, and consequently the lower layers become crushed and thus obstruct the draft. On the other hand, the friability of asphaltic coke renders i t particularly suitable for pulverized fuel firing. Coke from batch coking stills consists chiefly of carboid coke, with some asphaltic coke from the upper part of the still. Knowlea oven coke usually consists entirely of carboid coke. Such products withstand handling and transport well, and are suitable for industrial firing in lump form. They are also in demand for the production of electrodes and other forms of industrial carbon. In short, asphaltic coke and carboid coke are separate and distinct products, almost as different as coal and coal coke Users of petroleum coke should bear this fact in mind and specify the type of product which best suits their purpose. The two types are distinguished by their content of volatile matter and asphaltenes. For example, a commercial grade of carboid coke might be required to have a volatile content below 7% and contain less than 3% of material soluble in trichloroethylene. ACKNOWLEDGMENT
The authors’ have profited by valuable criticism from H. H* Lowry, and they wish to thank the Chairman and Board of Trinidad Leaseholds Ltd. for permission to publish this paper.
INDUSTRIAL AND ENGINEERING CHEMISTRY
1144
LITERATURE CITED
(1) Abraham, H., “Asphalts and Allied Substances”, 4th ed., p. 1011 (1938). (2) Asahara, G . , Sci. Papera Inat. Phy8. Chem. Resmrch (Tokyo), 1, 23 (1922); Japan. J. Chetn., 1, 35 (1922). (3) Biaatoch, K.,and Hofmann, U., Angew. Cham., 53,327(1940). (4) Bolton, K.,Cullingwortb, J. E., Ghosh, B. P., and Cobb, J. W., J. Chem. SOC.,262 (1942). (6) Debye, P., and Scherrer, P., Physik. Z . , 18,291 (1917). (6) Dennstedt, M.. “Anleitung zur vereinfachten Elementaranalyae”, 4th ed., p. 68 (1919); Houben, J., “Die Methoden der organischen Chemie”, Vol. 1, p. 109 (1925). (7) Gibson, J., and Riley, H. L., Fuel, 21,36 (1942). (8) Hofmann, U.,Bsr.. 65B,1821 (1932). (9) Hofmann, U.,Groll. E., and Lemcke, W., 2. angsw. Cham., 44, 841 (1931). (10) Hofmann, U.,and Lemcke, W., 2. anorg. aZZgem. C h m . , 208, 194 (1932). (11) Hofmann, U.,Ragoss, A., and Sinkel, F., KollOid-Z., 96, 231 (1941). (12) Hofmann, U.,and Wilm, D., 2.Etedrochem., 42,604 (1936). (13) Hofmann, U.,and Wilm, D., Z . physik. Chem., B18, 401 (1932).
I
>‘-
Vol. 36, No. 12
(14) Koch-Holm, E., Wiss. Vw65ent. Sinens-Konsan, 6,188(1927). (16) KohlachUtter, V., 2. anorg. Cham., 105,36 (1919). (16) Lowry, H. H.,J . Am. Chem. Soc., 46,824 (1924). (17) Lowry, H. H., J. Phur. Cham., 33, 1332 (1929). (18) Lowry, H. H., Landau, H. G., and Naugle, L. L., Trona. A m . Inat. Mining Met. Bngro., 149,297 (1942). (19) Marcusaon, J., 2. angsw. Chem., 29, 346 (1916). (20) Mekler, L. A., Fuel8 and Furnaces, 5 (1927). (21) Miwa, M.;Science Repts. Tdhoku I m p . Unio., 23, 242 (1934). (22) Morrell, J. C., and Egloff, Gustav, Chemistry & Industry. 51. 467 (1932); Univcrsd Oil Produdo Booklet 111. (23) Nellensteyn, F.J., Proc. World Petroleum Congr., 2, 618 (1933). (24) Riley, H. L., Chemistry & Induotry, 58,391 (19391. (25) Sakanov, A. N., and Vssil’ev, N. A,, Gosudartawennae Nauch.Tekh. Iadotelstvo Moscow-Petrograd, 1931, 265; Chem. AbSh‘oC&, 28, 298 (1934). (26) Stroud, W. F.. in “Science of Petroleum”, Vol. 4, p. 2772, London, Oxford Univ. Preas, 1938. (27) Tilirheyev, M. D.,J. Applied Chsm. (U.S.S.R.), 12, 1402 (1939); Chem. Abskada, 35, 2699 (1941). (28) Warren, B. E.,J. Cham. Phys., 2, 561 (1934). (29) White, A. H., and Oermer, L. H., Zbid., 9,492 (1941).
VAPOR-LIQUID EQUILIBRIUM CONSTANTS FOR
Benzene,
50
20
Toluene, and
10
Methyl-
I
d
2
cvclohexane d
I
V
0.5
APOR-liquid equilibrium constants may be defined by the equation :
K = ylz 0.2
where y = mole fraction of a component in vapor phase mole fraction of a component in liquid phase 2 From the fugacity rule of Lewis and Randall (6) for ideal solutions:
0.1
XfL = YfV 0.05
where fL = fugacity of pure component in liquid phase at temperature and pressure of system fv = fugacity of pure component in vapor phase at temperature and pressure of system
0.02
PRESSURE QOI
POUNOS PER 10
20
SQUARE
INCH
50
Figure I
ABSOLUTE IW
200
600
The fugacity of the vapor is available when the reduced temperature and pressure are known. The fugacity of a pure component in the liquid phase is equal to its fugacity in the vapor phase when the total pressure of the system equals the vapor pressure of the pure component at the
