INDUSTRIAL AND ENGINEERING CHEMISTRY
January, 1943
TABLE11. SUMMARY OF EXPERIMENTAL DATAON MITHYLCYCLOPENTANEBENZENE Equilibrium Determinations Mole fraction methylcycloRelative pentane Liquid Vapor volatility, a
0.0297 0.1080 0 1751 0:3017 0.3806 0.4460 0 5031 0:5737 0.6434 0.7206 0.7855 0.8224 0.8441 0.8721 0.9030 0.9180 0.9296 0.9373 0.9450 0.9518 0.9515 0.9613
0.0526 0.1668 0 2533 013870 0.4598 0.5179 0.5673 0.6255 0.6795 0.7442 0.7986 0.8299 0.8499 0.8754 0.9034 0.9174 0.9287 0.9360 0.9442 0.9503 0.9505 0.9602
1.814 1.653 1.598 1.461 1385 1.340 1.295 1.241 1.175 1.128 1.083 1.054 1.046 1.030 1.005 0.992 0.988 0.978 0.985 0.968 0.979 0 971
Boiling Points .Mole fraction methylcycloC. a t pentane 760 mm. 80.10 0.0000
0.0297 0.1080 0.1443 0.1751 0.3017 0.3806 0.4450 0.5737 0.6434 0.7206 0,8224 0.8510 0.9030 0.9174 0.9034 0.9180 0.9360 0.9373 0.9422 0.9442 0.9450 0.9518 0.9515 1.0000
Known Mixtures Mole frsotion methylcyolopentane n v
79.64 77.62 77.15 76.62 74.85 74.00 73.43 72.84 72.06 71.97 71.54 71.53 71.47 71.50 71.39 71.53 71.60 71.65 71.56 71.62 71.68 71.80 71.84 71.80
expected to form ideal solutions. Fractions through the pentanes are separated in pure form by efficient fractional distillation. Hexane fractions have given considerable difficulty in the separation of their pure components (S), and in general the components in the pure state are not obtainable by fractionation alone. However, Bruun (6) was able to a 55-650 c* Out into isomeric reso1ve anes by distillation in 52-phte and 100-plate Columns. Tongberg, Fenske, and Sweeney (15) reported in 1938 that no true constant-boiling mixture had been found in twenty virgin aromatic-nonaromatic mixtures behaved naphthas, abnormally in distillation. It is apparent that the presence of aromatics greatly interferes with separation by fractional distillation. The cut to contaihed no During Bruun was the past few years, aromatics have been removed by nitration or azeotropic distillation before ultimate fractionation was attempted.
Binary Systems Containing Aromatics It has long been established that benzene-toluene form nearly ideal solutions. Toluene-xylene and the ternary mixtures with benzene do also (9). Beatty and Calingaert (1) reported that the toluene-ethylbenzene system is nearly ideal. On the other hand, all reported that aromatic-naphthene and aromatic-paraffin systems deviate widely from regularity of solution. The existence of a benzene azeotrope with methylcyclopentane is established in this paper. Scatchard, Wood, and Mochel (IS) took accurate isothermal data on the benzenecyclohexane system, which shows an azeotrope having a composition of approximately 50 mole per cent benzene a t 70’ C. Quiggle and Fenske reported data on the methylcyclohexane-toluene system (12). While it deviates greatly from ideality, it does not form an azeotrope. Tongberg and Johhston (16), studying the equilibrium of n-hexane-benzene, reported no separation obtainable a t concentrations above 97 mole per cent hexane. Although a minimum-boiling -ture was not observed, the presentauthors are of the opinion that one exists having a boiling point &hin 0.10 c. of pure n-hexane, which thereby escaped detection. Otherwise this is the first pseudo-azeotrope to be established with modern fractionating equipment. Bromiley and Quiggle
0.0547 0.1343 0.1616 0.2096 0.3857 0.4851 0.6159 0.7486 0.7871 0.8316 0.8435 0.9366
1.49333 1.48432 1.48120 1.47553 1.45794 1 44896 1.43820 1.42749 1.42486 1.42175 1.42138 1.41452
119
(9) studied n-heptane and n-octane with t o l u e n e . No a z e o t r o p e s formed, but the shape of both 9-x curves was similar to that of methylcyclohexane-toluene, in that the r el a t i v e volatility decreased abnormally as the aomposition approached the pure low-boiling component. The existence of benzene azeotropes and the abnormally low relative volatility of toluene in certain concentrations with both lower and higher boiling compounds is considered an adequate explanation for the failure of good fractionation equipment to resolve six- and sevencarbon petroleum fractions into their pure components when aromatics are present.
Acknowledgment E. P. Schoch, of the Bureau of Industrial Chemistry, University of Texas, generously loaned the distillation equipment and encouraged the work. Thanks are due George Scatchard for review and criticism of the manuscript.
Literature Cited (1) Beatty and Calingaert, IND.ENQ.CHEM.,26, 504,904 (1934). (2) Bromiley and Quiggle, Ibid., 25, 1136 (1933). (3) Bruun and Hicks-Bruun, Bur. Standards J . Research, 5, 933 (1930). (4) Ibid., 6,577 (1931). (5) Bruun, HicbBruun, and Faulconer, J . Am. Chem. Sot., 59, 2355 (1937); 61,3099 (1939). (6) Evans, J . Inet. Petroleum Tech., 24, 332 (1938). (7) Fenske, M. R.,in “Physical Constants of the Principal Hydrocarbons”, 2nd ed., p. 73,Texas Co., 1939. (8) Garner and Evans, J. Inst. Petroleum Tech., 18,761 (1932). (9) Griswold, J., Sc.D. thesis, Mass. Inst. Tech., 1931. (10) Othmer, D.F., IND. ENQ.CHEM.,ANAL.ED., 4, 232 (1932). (11) Podbielniak, W. J., Ibid., 13, 639 (1941). (12) Quiggle and Fenske, J . Am. Chem. SOC.,59, 1829 (1937). (13) Scatchard, Wood, and Mochel, J . Phys. Chem., 43,119 (1939). (14) Smittenberg, Hoog, and Henkes, J. Am. Chem. SOC.,60, 17 (1938), (15) Tongberg, Fenske, and Sweeney, IND.ENQ. CHEY.,30, 169 Tongberg (1938). and Johnston, Ibid., 25, 733 (1933). (17) vogei, A. I., J . Chem. SOC., 153, 1323 (1938). (18) Vondracek, Collection Czechoszav. Chem. Commun., 9,521 (1937). (19) Wibaut et al., Rec. trav. chim., 58, 329 (1939). (20) Willard and Crabtree, IND.ENG. CHEM.,ANAL. ED., 8, 79, (1936). (21) Wojciechowski, M.,J . Research Natl. Bur. Standards, 19, 347 (1937). (22) Zelinsky and PoUak, Ber., 65, 1171 (1932).
Infrared Radiant Heating-Correction It has been pointed out to the writers that a mistake in calculation arises in connection with Figure 8 on page 778 of the July, 194% issue. The ordinate of Performance should be multiplied by the factor 0.86. It should also Liavebeen specifically pointed out that the initial stock temperature was 80’ F. F.
TILLER
Vanderbilt University Nashville, Tenn.
H. J. GARBER University of Cincinnati Cincinnati, Ohio
