Qecember 1950
INDUSTRIAL AND ENGINEERING CHEMISTRY
(31) Steffen, H. C.,India Rubber World, 120,60-2 (1949). (32) Stevens, H. P., Rubber Chem. TechnoZ., 12, 610-31 (1939). (33) Taft, W.K., and Alden, G. E., “Effect of Banbury Loading on Breakdown of Polymers Made at Low Tempcratures,”
private communication, Government Laboratories to Office of Rubber Reserve. (34) Taft, W. K., and Goldsmith, H., “Alfin-Catalyzed GR-S Type Polymers,” ~ N D .ENG.CHEM.24, 2542 (1960). (35) Tuley, W.F.,Rubber Age, 64, 193-6 (1948).
2569
(36) White, L. M., IND. ENG.CHEM., 41,1554-5 (1949). (37) Williams, I.,Zbid., 19,674-7 (1927). (38) Zwicker, B. M.G., et aZ.,“Hot Processibility of Low Temperature Polymers,” private communication, B. F. Goodrich Chemical Co. to Office of Rubber Reserve. RECEIVED April 13, 1950. Work carried out under the sponsorship of the Office of Rubber Reserve, Reconstruction Finance Corporation, in connection with the government synthetic rubber program.
Vapor-Liquid Equilibria at Subatmospheric Pressures TRICHLOROETHYLENE-TETRACHLOROETHYLENEAND ETHYLPHENYL ACETATE-ETHY L a-PHENYL BUTYRATE KENNETH C. BACHiMAN, ADOLPH ZIMMERLI, AND EDWARD L. SIMONS Rutgers University, Now Brimswick, N . J . Vapor-liquid equilibrium data at subatmospheric pressures have been obtained for the binary systems trichloroethylene-tetrachloroethylene and ethyl phenyl acetate ethyl a-phenyl butyrate, and the variation with pressure of the relative volatility has been calculated. The vapor pressure-temperature relationships for ethyl phenyl acetate and ethyl a-phenyl butyrate have been determined.
N CONNECTION with the problem of setting up a series of student experiments on vapor-liquid equilibria and distillation, an investigation was made of the binary systems composed of trichloroethylene and tetrachloroethylene and of ethyl phenyl acetate and ethyl a-phenyl butyrate a t subatmospheric pressures. These were chosen as examples of systems with markedly different relative volatilities which might also display nearly ideal behavior. The latter system, with a relative volatility of about 1.5, should ;)2 suitable for the investigation of the performance, under reduced pressure, of laboratory columns of from 5 to 20 theoretical plates. The two esters are commercially available in high purity and a t reasonable cost.
The trichloroethylene and tetrachloroethylene were stored in dark bottles in a cool place, and all experiments using these substances were run while shielded from direct window or artificial light. Attempts to determine the normal boiling points of ethyl phenyl acetate and ethyl a-phenyl butyrate were unsuccessful because on continued, recycling through the equilibrium still the liquids gradually darkened in color, indicating some decomposition. The vapor pressure-temperature equations deter-
TABLE 11. SPECIFIC GRAVITIESOF MIXTURESOF TRICHLOROETHYLENE A N D TETRACHLOROETHYLENE AND OF ETHYLPHENYL ACETATEAND ETHYL CY-PHENYL BUTYRATE Ethyl Phenyl Acetate and Butyrate _.Tri- and Tetrachloroethylene SP. gr., Ethyl phenyl acetate SP. gr., Trichloroethylene Mole % Weight % d:’ Mole % Weight % d:’ ’.98856 0.00 0.00 1.6241 0.00 0.00 1.99524 20.03 17.62 1,5947 16.62 20 13 .00224 39.64 35.94 1,5640 34.47 39:90‘ 46.10 .00616 50.03 1 ,5326 54.34 60.03 56.56 .01011 60.39 1,4905 76.24 80.20 77.75 .01850 80.36 1.4652 100.00 100.00 ,02710 100.00 100.00
MATERIALS
The four liquids used in this study were obtained from conimerrial sources and purified by fractionation as follows: The trichloroethylene and tetrachloroethylene wcre passed through a packed column of five plates at a reflux ratio of 6 to 1,and the ethyl phenyl acetate and ethyl a-phenyl butyrate were passed through a packed column of twelve plates a t a reflux ratio of 12 to 1 a t a pressure of 15 mm. of mercury. In each case the heart cut was collected and its physical eonstants were memurcd. These are listed in Table I along with previously puhlishcd vnlucs.
d
mined during this investigation were used to extrapolate the data to 760 mm. These extrapolated values of the boiling point are listed in Table I. ANALYTICAL METHOD
Equilibrium sitmples of liquid and vapor condcnsatc were analyzcd by specific gravity measurements which were made using an Ost,wald-typc pycnometer of 10-ml. capacity. Values of the specific gravitics of known mixtures are presentcd in Table 11.
TABLE I. PHYSICAL CONSTANTS OF MATERIALS
Liquid Trichloroethylene Tetrachloroethylene Ethyl phenyl acetate Ethyl u-phenyl butyrate
Boiling Point. C. Exptl. Lit. 86.8-87.0 86.95
Specific Gravity Exptl. Lit. 1.4652:O 1.4649:O
EQUILIBRIUM MEA SUREMEN‘I’S
LiteraRefraotivo Indcx ture ExptlL1t. cited 1.4776L0 1.47771BD.* (1.6)
120.6-120.8 120.8
1 ,6241:’
1 6226:’
l..iO56~1.50547%’
(9,8)
226.4
227.1-227.6
1.02710:’
1.029:’
1.4955%’ 1 4053g
(1.4)
238.6
....
0.98856:5
... .
1.48799
.. ..
..
The apparatus uscd to dctcrmine vapor-liquid equilibrium data consisted of a glass Othmer still ( 1 0 ) connerted through a ballast bottle and a manually operated barostat to a vacuum rnanifold. Pressure measurements were made with an open-end manometer, and temperature measuremcnts were made with
INDUSTRIAL AND ENGINEERING CHEMISTRY
2570
a &inch immersion mercury-in-glass thermometer graduated in 0.1 C. The still body and vapor neck were lagged with a thick coating of asbestos; heat was supplied from a gas microburner which was directed at the wire gauze wound around the glass loop on the still pot. All ground-glass joints and stopcocks were lubricated with silicone grease. The manipulation of the still has been described (7). With a charge of 450 ml. in the still pot and a vapor receiver capacity of 20 ml., constancy of temperature was attained within 60 to 90 minutes. After removing the flame and simultaneously bringing the system to atmospheric pressure, samples of pot liquid and condensate \yere withdrawn into chilled flasks and were analyzed. O
VAPOR PRESSURE MEASUREMENTS
Calculations of the ideal relative volatilities and activity coefficients for a binary system require vapor pressure data for the pure components. For trichloroethylene and tetrachloroethylene the data of Stull ( 1 % )were used; these data may be represented by the following equations:
+ 7.7361 1954.9/1' + 7.8438
Vol. 42, No.
2
-
760700 600
500 400
-
300-
200
-
f E.
WIOOf 90-
2 807060
-
40 50
Trichloroethylene, log,,p(mm.) = - 1746.3/1' Tetrachloroethylene, log,op(mm.) =
-
Since no similar data were available for ethyl phenyl acetate and ethyl a-phenyl butyrate, they were determined in the same still which was used for the equilibrium studies by measuring the bailing point at various pressures. For pressures below 100 mm., readings were made on a Zimmerli gage ( I S ) . The data, listed in Table I11 and plotted in Figure 1, may be represented bj. the followin'g equations obtained by the method of least squares:
x)-
20
-
.io
10;s
I
I;.
1
.2P .23 111x 100
I
.P4
I
.25
.!
+ 8.5339 Ethyl a-phenyl butyrate, loglop(mm.) = -2892.4/1' + 8.5318 Ethyl phenyl acetate, loglop(mm.)
=
-2818.7/1'
TABLE 111. VAPORPRESSURES OF ETHYL PHENYL ACETATEA N D ETHYL CY-PKENYL BUTYRATE Ethyl Phenyl Acetate
c.
k.
120.1 131.9 142.3 155,6 178.5 183.2 186,9 191.9 193.0 202.0
0.2543 0.246E 0,2407 0.2332 0.2214 0.2191 0.2173 0.2150 0.2145 0.2104
t,
-
lo*p , mm. ~g
23.5 37.6 56.7 91.8 198.2 229.4 256.0 294.9 305.6 393.9
Ethyl a-Phenyl Butyrate-_1 t.0 C. T,OA. lo* p , mm. Hg 131.2 0.2473 23.8 0,2448 135.4 28.4 0.2376 147.7 45.7 0.2320 157.8 66.2 0.2268 167.7 93.2 190.9 0.2155 201.0 0.2092 204.9 304.7 0.2047 215.4 403.7
binary systems. Thc solid wrves represent the Raoult's law distribution, and the cmircles reprcsent the experimental points. For each system the o t h u isolwic plots are of the same form, displaced only s!ight,ly froni c . a c b h other. The boiling point-voniposition curves are of the siniplwt t l p e fov 110th systems.
VAPOR-LIQUID EQUILIBR1U.M DATA
The experimental results obtained for the various isobars arc presented in Tables I V and V; these tables also give the values oi the relative volatilities and activity coefficients which Jvere calculated from the follo-ing relationships:
y = mole fraction in vapor phase x = mole fraction in liquid phase p o = vapor pressure of pure component a t boiling poirit ot solution P = total still pressure Subscript 1 refers to more volatile component Subscript 2 refers to less volatile component
The nature of the vapor-liquid distribution is shown in Figure 2 whirh represents g - x piots for the 380-mm. isobars of both
'0
0
x) 40 50 60 TO 80 MOLE PER CENT M O R E VOLATILE IN LIQUID
20
90
I00
Figure 2. Vapor-Liquid Equilibrium Diagrams for Binary Systems Trichloroethj lene-Tetrachloroethylene and Ethyl Phenyl Acetate-Eth>l a-Phenyl Butyrate a t 380 M m . of Mercir ry
0 Experimental
-
points
Raoult's law curve
INDUSTRIAL AND ENGINEERING CHEMISTRY
December 1950
2571 DISCUSSION
EQUILIBRIUM DATAFOR SYSTEM TRICHLOROETHYLENETETRACHLOROETHYLENE AT VARIOUSPRESSURES
TABLE IV. Boiling Point, t,Q
c.
Trichloroethylene. Mole % Liquid Vapor
Activity Coefficients Relative Volatility aeXpt, ~ ~
d yi ~
~YP
l
yi
760 Mrn. 12U.7 111.3 107.7 104.2 100.9 99.0 97.0 94.1 92.8 86.9
0.0 17.5 26.2 34.8 43.4 48.7 55.4 67.0 72.9 100.0
0.0 38.6 51.2 61.5 69.9 74.2 79.0 85.6 88.5 100.0
98.2 86.4 83.0 80.2 79.1 77.0 76.6 75.8 75.2 73.8 72.0 70.9 65.5
0.0 21.6 29.6 37.4 41,l 48.1 50.0 52.7 54.8 60.7 67.2 73.1 100.0
0.0 44.7 56.4 65.2 68.8 74.6 76.0 77.6 79.3 82.7 86.3 89.4 100.0
78.1 66.8 64.3 61.3 58.6 57.2 56.1 54.9 53.9 50.9 46.8
0.0 20.6 25.2 33.0 43.1 48.4 53.6 57.6 63.1 70.2 100.0
0.0 46.8 51.7 61.7 71.8 75.6 79.4 81.8 85.1 88.8 100.0
2,723 2.754 2.787 2.819 2.838 2.855 2 .a87 2.9%
1.07 1.05 1.05 1.05 1.05 1.04 1.01 1 .oo
0.98 0.98 0.97 0.97 0.98 0.98 1.00 1.01
1.09 1.07 1.08 1.08 1.07 1.06 1.01 0.99
+0.0374 f0.0294 +0.0334 4-0,. 0334 -I-0.0294 +0.0253 +0.0043 -0.0044
1.04 1.07 1.06 1.06 1.05 1.04 1.04 1.04 1.03 1.03 1.01
1.05 1.04 1.03 1.02 1.01 1.01 1.03 1.02 1.03 1.05 1.03
0.99 1.03 1.03 1.04 1.04 1.03 1.01 1.02 1.00 0.98 0.98
-0.0044 f0.0128 +0.0128 ‘to. 0170 +O. 0170 f0.0128 f 0.0043 +O. 0086 0.0000
1.06 1.07 1.08 1.07 1.05 1.04 1.04 1.03 1.08
1.07
0.99 0.98 0.99 1.03 0.99 0.98 0.95 0.94 1.04
- 0.0044 - 0.0088
380 Mm. 2.93 3.08 3.14 3.16 3.17 3.17 3.15 3.15 3.10 3.08 3.10
2.968 2.988 3.03s 3.051 3.076 3.082 3.091 3.098 3.115 3.138 3.153
-- 0.0088 0.0088
190 AIm. 3.205 3.239 3.28 3.32 3.34 3.35 3.38 3.39 3.43
1.09 1.09 1.04 1.06 1.06 1.09 1.10 1.04
-0,0044 +0.0128 - 0.0044 - 0.0088 -0.0223 - 0.0269 $0.0170
TABLEV. EQULIBRIUM DATAFOR SYSTEM ETHYLPHENYL ACE TAT^ETHYLWPHENYL BUTYRATE AT VARIOUSPRESSURES Boiling Point, t,o
c.
Why1 Phenyl Acetate, Mole % Liquid Vapor
~_
213.1 210.8 209.0 207.8 207.0 205.4 204.6 203.9 200.4
0.0 17.0 29.7 41.8 43.5 55 1 64.1 70.9 100.0
0.0 ,22.9 37.8 30.6 52.2 63.7 71.6 77.4 100.0
189.6 184.9 184.4 183.6 182.9 181.9 180.7 180.1 177.5
0.0 29.4 34.6 42.0 47.4 55.6 64.6 69.0 100.0
0.0 37.7 43.8 .51.2 07.0 64.7 72.3 76.28 100.0
0.0 27.6 39.1 48.2 56.0 63.3 69.6 100.0
0.0 36.6 49.4 59.0 66.2 72.3 77.6 100.0
.4rtivity Coefficients Relative Volatility
1.45 1.44 1.43 1.42 1.43 1.41 1.40
1.427 1.429 1.430 1.431 1.433 1.433 1.434
1.01 1.00 0.98 0.99 1.01 0.99 0.99
1.00 0.99 0.99 1.01 1.02 1.01 1.01
1.01 1.01 0.99 0.98 0.99 0.98 0.98
+O. 0043
4-0.0043 - 0.0044 - 0.0088 - 0.0044 -0.0088 - 0.0088
190 M m . 1.45 1.47 1.47 1.47 1.46 1.43 1.44
1,455 1.456 1.457 1.458 1.459 1.461 1.461
1.52 1.52 1.55 1.54 1..52 1.51
1.480 1.481 1.483 1.484
1.02 1.02 1.01 1.01 1.01 1.01 1.02
1.02 1.01 1.01 1.01 1.01 1.04 1.04
1.00 1.01 1.00 1.00 1.00 0.97 0.98
0.0000 i-0,0043 0.OOoa 0,0000 0.0000 -0.0132 - 0,0088,
1.00 0.99 1.00 0.99
0.98 0.97 0.96 0.96 0.98 0.99
1.02 1.02 1.04 1.03’ 1.01 1.02
+ O . 0086
0.96 0.98 0.97 0.95 0.97 0.96
1.09 1.06 1.07 1.08 1.06 1.06
-I-0.0374 1-0.0253 4-0.0294 +O. 0334 -I-0.0253 +0.0253
z2 !%
++O.0.0086 0170 +0.0128 +4-0.0086 0.0043
47.5 M m . 148.8 144.8 144.0 143.2 142.6 141.4 140.6 137,7
0.0 31.2 36.7 13.5 61 .o 59.1 68.6 100.0
0.0 42.9 48.4 55.7 63.2 70.1 77.9 100.0
I 66 1.62 1.64 1.65 1.63 1.61
1.508 1.500 1.611 !.5li 1.513 1.514
ACKNOWLEDGMENT
The authors wish to acknowledge the support given to this investigation by the Research Council of Rutgers University. LITERATURE CITED
95 Mm. 168.2 164.9 163.8 162.7 161.8 160.8 159.6 156.7
The close fit of the experimental points to the Raoult’s Iaw,curve, as shown in Figure 2, suggests the possibility of ideal behavior for these systems. For vapor-liquid equilibrium studies t h e extent of any deviations from ideal behavior may be expressed in terms of the activity coefficients, 71 and yz, calculated from Equations 3 and 4 on the assumption of an ideal vapor phase. An examination of these deviation factors within each isobar shows a slight fluctuaticn with composition which is different from the regular and consistent type of deviation characteristic of nonideal systems, as discussed by Carlson and Colburn (6). Sucah variations as these in the neighborhood of unity, with, no significant trend to higher values of y, have been used as a criterion for ideality in the system ethylene dichloridetoluene as reported by Jones, Srhoenbrun, and Colburn (9). Redlich and Kister (11)have used the variation with composition of log yI/yz as a basis for the classification of solutions, and in this scheme an ideal system is characterized graphically by the zero line in the log yl]yl against z plot. The log y1/y2 values for the isobars reported herein show no trend with composition, and their deviations from zero are of the same magnitude as those reported by Redlich and Kister to demonstrate the ideal nature of the s y s t e m 2,2,4trimethylpentane-methylcyclohexene at 741 mm. Considering the isobars in the light of the above criteria, both systems are close to ideal in their behavior; the deviations seem to increase with increasing .pressure in the chloroethylene system and to increase with decreasing pressure in the ester system. I n both systems the relative volatility increases as the pressure is reduced.
Beilstein,, “Handbuch d e r o r g a n i s c he n Chemie,” Vol. 9, p. 434,New York, G.E. Stechert & Co., 1926. Zbid., 1st supplement, Vol. 1, p. 78, 1928. lbid., p. 80. Zbid., Vol. 9,p. 173, 1932. Zbid., 2nd supplement, Vol. 1, p. 160, 1941. Carlson, H. C., and Colburn, A. P., IND ENG.CHEM.,34, 681 (1942). Gilmont, R.,and Othmer, D. F., Zbid., 36, 1061 (1944). “International Critical Tables,” Vol. 7, p. 34, New York, McGraw-Hill Book Co., 1930.
Jones, C. A., Schoenbrun, E. M., and Colburn, A. P., IND. ENG. CHEM.,35, 666 (1943).
1.05 1.04 1.04 1.03 1.03 1.02
Qthmer, D. F., Zbid., 35, 614 (1943). Redlich, O.,and Kister, A. T., Ibid., 40,345 (1948).
Stull, D: R., Zbid., 39,517 (1947). Zimmerli, A., IND.ENG.CHEM.,ANAL.ED., 10,283 (1938). , RECEIVIDD April 29. 1950.
