1284
INDUSTRIAL AND ENGINEERING CHEMISTRY ACKNOWLEDGMENT
empirical equations were developed for the region between the solutrope and the plait point. At 20" C. the expression is a / b = 1.068~ 0.087. At 0" C. the expression is a / b = 1 . 2 4 2 ~ 0.047. Here a = weight fraction of teit-butyl hypochlorite in the tert-butyl hypochlorite layer, and b = water in the water layer. Although there is some analogy between a solutrope and an azeotrope, the analogy does not extend far. During ordinary distillation of a mixture vihich can form an azeotrope, the azeotrope represents the best product purity obtainable. However, during countercurrent liquid-liquid extraction, the solutrope does not limit the purity of product. The cost of carrying out a commercial extraction will be influenced by solutrope occurrence. Separations will be much easier to carry out on one side of the solutrope composition than on the other. This becomes apparent when the usual graphical methods are applied to typical problems for this ternary system. The phase diagrams must be considered as unexplored in the region near 100% alcohol. A solid phase should appear because the alcohol freezes at 25.5' C. Only liquid phases n-ere found to exist in the composition mea actually investigated.
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Vol. 46, No. 6
This investigation was carried out under the sponsorship of the Office of Ordnance Research, Contract DA-11-022-ORD828. The helpful suggestions of Ervin Colton and of Mark >I. Jones of this laboratory are acknowledged.
+
LITERATURE CITED
(1) Chattaway, F. D., and Backeberg, 0. G . , J . Chem. Soc., 123, 2999-3003 (1923). (2) Colton, E., Jones, AI. JI., and Audrieth, L. F., "Formation of Hydrazine from tert-Butyl Hypochlorite and Ammonia," J . Am. Chem. SOC.,in press. ( 3 ) Smith, A. S.,IND. EXG.CHEM..42, 1206-9 (1950). (4) Smith, J. C., Stibolt, V. D., and Day, R. W., I h i d . , 43, 190-4 11951). (5) Tekter, H. M., Bachman, R. C., Bell, E. W., and Cowan, J. C., Ibid., 41, 849-52 (1949). (6) Teeter, H. M., and Bell, E. W., OTQ.Syntheses, 32, 20-2 (1052). (7) Treybal, R. E., Weber, L. D., and Dales, J. F.,ISD. ENG. CHEM., 38, 817-21 (194G). RECEIVED for review October 1'9, 1963. ACCEPTEDJANUARY 28. 1964. Presented before t h e Division of Industrial and Engineering Chemist,ry a t the 125th IIeering of the AMERICASCIIEXICALSOCIETY, Kansas City, 310.
W. S. W'HITE AND MATTHEFT VAN WINKLE Unizersity of Texas, 4ustin 12, Tex. PROCEDURE
APOR-liquid equilibrium behavior of the system et'hylbenzene-styrene is of interest because i t is encountered in t,he process from n-hich styrene is produced from ethylbenzellc. Styrene must be obtained from this mixture in a highly pure form for polystyrene manufacture and other applications. Normally t,he separation is obtained by fractional distillation under conditions wherein excessive thermal polymerization of the st?'rene can be inhibited. Fractionation of the ethylbenzene-styrene mixture under subatmospheric pressures lowers the temperature level of the separation process and should aid in reducing the thermal polymerization tendency. The purpose of this investigation was t o determine the vapor-liquid equilibrium data of the system in question a t 100 mm. of mercury absolute pressure.
still n.as used to modified Colburn ($) type of obtain the equilibrium vapor and liquid sanlples. The stili iliodifications and the operational procedure have been described (3.4,8 ) . liept in storage a t 4 o c F. to inhibit The styrene sample polymerization and frequent checks of index of refract,ion were run to ensure that no changes in t,he sample had taken place. yosample containing styrene TTas ailolved to in the still for longer than hour and no sample 7 ~ are-used. s RESULTS
Equilibrium vapor-liquid compositions determined in thia investigation are reported in Table I1 along x i t h the activity coefficient, data calculated from the experimental results. The experimental data are also presented in Figure I as a
MATERIALS
Both the ethylbenzene and styrene v,-ere obtained from the Monsanto Chemical Co. The properties of these materials are given in Table I.
TABLE
I.
PROPERTIES O F AIATERL4LS
Ethylbenzene Exptl. Lit.
ANALYTICAL METHODS
Vapor a n d liquid samples were analyzed by means of index of refraction, using a Bausch & Lomb precision refractometer with a monochromatic
Refractive index, n~5; Boiling point, c, 760 mm.
sodium d line light source. Conipositions were read from a calibration curve of composition versus refractive index experimentally determined from samples of known composition.
Bntoine equation
100 mm.
c.
1.4932
-
Styrene Exptl. 1.5433
1.4933(6)
Lit. 1.5436-1.6439(1)
136.3
136.19(6, 6)
145.3
145.2(6)
74.05
74.11(6)
82.1
143.0(7) 82.0(7)
Log.oP
= 6.95366
-
1421.9 14 212.931 t"C. (6) Z O ~ I O=P7.2788 ~
1649.6
- 230 __-+ t°C.
99.3 99.8 Purity, % Sample contained less t h a n 0.001'X polystyrene and 12 p.p.m. of polymerization inhibitor.
(')
INDUSTRIAL AND ENGINEERING CHEMISTRY
June 1954
740
IO
20
40 50 6 0 70 80 MOLE PERCENT ETHYL BENZENE
30
90
1285
100
Figure 1. Equilibrium Boiling Point Diagram for Styrene-Ethylbenzene System a t 100 M m . of Mercury MOLE PERCENT ETHYL BENZENE
temperature-composition diagram at 100 mm. of mercury pressure and in Figure 2 as equilibrium vapor composition versus liquid composition.
IN LIQUID, X
Figure 2. Vapor-Liquid Equilibria Diagram for Styrene-Ethylbenzene System a t 100 Mm. oifilercury 1501
1
TABLE11. TAPOR-LIQUID EQUILIBRIUM
COMPOSITIONS AKD EXPERIafEST.4L ACTIVITY COEFFICIENTS FOR SYSTEM ETHYLBENZESE-STYREKE AT 100-MM.MERCURY PRESSURE
Mole Fraction Ethylbenzene Temp., O C. 74.05 74.25 75,03 76.19 76.98 77.86 78.64 79.33 80.15 80.72 82.10
Vapor 1.00 0.914 0.814 0.699 0.611 0.511 0.416 0.324 0.211 0.144 0.000
Liquid 1.00
0.887 0.764 0.619 0.522 0.412 0.319 0.235 0.141 0.091 0.000
Experimental Activity Coefficients YEB
yet
1.00 1.02 1.03 1.04 1.04 1.07 1.09 1.12 1.18 1.22
1.05 1.05 1.01 1.00 1.00 1.00 1.00 0.99 1.00
...
...
1.00
The activity coefficients for the two compounds were calculated from
0
IO 20 30 40 50 60 70 80 MOLE PERCENT ETHYL BENZENE IN LIQUID, X
90
100
Figure 3. Activity Coefficient Diagram for StyreneEthylbenzene System at 100 Mm. of Mercury accentuated because of the possible limit of error estimated to be 5 0 . 2 mole % and &0.05” C. The activity coefficient data show that the styrene tended to be more nearly ideal in its behavior than the ethylbenzene, although the deviation from ideality in the caSe of either compound in the mixture Tvas not great. LITER4TLiRE CITED
(1) Boundy, R. H., and Boyer, R. F., “Styrene, Its Polymers, Co-
where y
= activity coefficient
of the component in the vapor mole fraction of the component in the liquid PT = total pressure P = vapor pressure of the component a t the equilibrium temperature The activity coefficient-composition data are presented in Figure 3. Examination of the figures indicates that this binary mixture is essentially ideal in its behavior. There seems t o be a slight azeotropic tendency shown on the t - x diagram, which might be y
= mole fraction
x
=
polymers, and Derivatives,” New York, Reinhold Puhlishiug Corp., 1952. (2) Jones, C. A, Schoenborn, E. X., and Colburn, A. P., IND ESQ. CHEX, 35, 666 (1943). (3) Jordan, B. T., and Van Winkle, LI., I b i d . , 43, 2908 (1951). (4) Keistler, J. R., and Van Winkle, M.,I b i d . , 44, F22 (1952). (5) Lange, N. A, “Handbook of Chemistry,” 8th ed., Sandusky, Ohio, Handbook Publishers, Inc., 1952. ( 6 ) Satl. Bur. Standards, Circ. C461 (1947). (7) Patnode, W.,and Scheiber, W.J., J . Am. ChenL. Yoc., 61, 3449 (1939). (8) Rasmussen, R. R., and Van X n k l e , AI., IND.ENG.C H m r . , 42, 2121 (1950). RECEIVEDfor review November 16, 1953.
ACCEPTED February 17, 1954.
