J, Chem. Eng. Data 1982, 27, 281-282 (14) A " e , D. €ng. Scl. Data 1976, Item&. 76004. (15) Roxzkwkeya, S. I.; Temkin, M. I.J. AppHed Chem. USSR (Engl. Tram/.) 1846, 19, 30. (16) Lyderm, A. L. Madbon, WI, 1955, Unlverslty d WkKxMein college d Engherhg, -E Exp&wnt Statbn Report No. 3. (17) Leach, J. W.; Chappekeu, P. S.; Ldend, T. W. AIChEJ. 1868, 14,
281
(19) Mdkrup, J.; Rowlineon, J. S. Chem. Em. Sd. 1974, 29, 1973. (20) Qoodwin, R. D. M S Tech. Note ( U S . ) 1976, No. 684. (21) (kodwln, R. D. "On the Nonanalytlc Equation of State for Ethylene", U.S. Natlonal Bureau of Standards. private communication, 1976.
Recdvd for revlew March 3,1981. Revised manuscript recalved Decsrnbar 28, 1981. Accepted February 2, 1982.
568.
(18) F b , Q. D.; Leland, T. W. I d . €ng. Chem. fundem. 1970. 9 , 537.
Isobaric Vapor-Liquid Equilibria of Toluene-Butyl Cellosolve Mixtures K. Venkateewara Rao,' A. Raviprasad, and C. ChlranJivi Lbpartment of Chemical Engineering, Andhra University, Visakhapatnam 530003, India
Ilobark vapor-llquld oqufflbria of the system t o h m + h t y i ceHosohre at 760 f 1 mmHg have been reported. Thh system exMW posithre devlatlons from Raoult's law. The vapor compodtlon Is predicted from expwhental t-x data wlng the Wlkon quatlon as well as UNIFAC parameters. The W#ron quatlon predlcted the vapor compodtion well, whereas the UNIFAC method predlcted the vapor comporltlon wRh an average absolute error of 0.034 mok fraction. Toluene Is used as a diiuent for butyl cellosolve in its appiC cation as an industrial solvent. The vapor-liqu# equiUbrkrm data for the system toiuene-butyl cellosolve is of use in designing a solvent recovery system. So far the vapor-liquid equilibrium data of this system have not been reported. Hence, the vapor-liquid equilibrium data at 760 f 1 mmHg pressure are determined and reported here. Expwlmenial Section Matedab. Analytical-grade toluene from the British Drug H o w Co.(Indla) is double distilled in a laboratory distlilation column. Butyi cellosolve supplied by Naarden (Holland) is distRled under vacuum, and the middle fraction whose boiling point at atmospheric pressure coincides with that reported in the literature b collected and used. Table I compares the physical properties of the chemicals with the literature values. €qud#lbrkm Sf///.A vapor recirculating stll of Jones as modified by Ward ( 1 ) is used to determine the vapor-liquid equilibrium compositions. A stili with a total capacity of about 60 mL is used. The still and the experimental technique have been described elsewhere (2). When the equilibrium temperature is attained in the still, this temperature is maintained for 2 h to ensure equilibrium conditions. The equilibrium temperature is measured by using a standard mercury-inglass thermometer having an accuracy of fO.l OC. Ana-. The composition of the equilibrium samples is determined by refractive index. Refractive krdex meawements are taken at 30 f 0.1 'C for sodium light with an Abbe precision refractometer capable of reading up to 0.0005. Water from a constant-temperature bath maintained at 30 f 0.1 OC is circulated through the prism of the refractometer. The compositions in mole percent are determined from a standard 0021-9588/82/1727-0281$01.25fO
plot of refractive index vs. composltkn prepared earlier by Using mixtures of known composition. The maximum error in the composition measurement by refractive index is estimated to be f0.007 mole fraction.
Results and Discusdon The vapor-liquid equilibrium data at 760 f 1 mmHg pressue are presented in Table 11. The liquid-phase activity coefficient of each component is calculated from the expression
The fugacity coefficients are calculated by using the vMal equation truncated after the second term. The second virlai coefficient and molar volume data are estimated from Hayden and O'Connei (3)and Yen and Woods (4) correlations, respectively. The Antoine constants ( 5 ) for toluene and butyl cellosolve are modifled to fit the experimental boiling temperatures and are used to compute the vapor pressures. From the activity coefficient data it is found that this system exhibits small positive deviation from Raouit's law. The data are found to be consistent by the point-to-point method (6). The Wilson equation (7) and the UNIFAC method are used to predict the vapor compositions from t-x data. As the fuand the Poynting factor in eq 1 gacity coefficient ratio 41V141s are found to be around unity, these correction factors are neglected in the prediction of vapor composition by the two methods. I n the case of the Wilson equation, a nonlinear least-squares minimizatlon procedure ( 8 )which optimizes Wilson parameters while predicting the vapor compositions is used with the foC lowing objecttve functlon:
The estimated vapor composition is presented in Table 11. The 0 1982 American Chemical Society
282 Journal of Chemkal and E n g M n g Data, Vol. 27, No. 3, 1982
Table I. Physical Properties of the Chemicals Used bP, “C
refractive index
chemical
exptl
lit.
ref
exptl
lit.
ref
vapor press. eq
ref
toluene butyl cellosolve
110.6 170.6
110.6 170.6
I1
1.4912at 30°C 1.4190 at 25 “C
1.4912at 30°C 1.4190 at 25 “C
11
logP=6.95105- 1342.310/(t + 219.187) logP= 7.84562 - 1988.900/(t t 230.000)
5 5
12
I2
Table 11. Vapor-Liquid Equilibrium Data for the System Toluene-Butyl Cellosolve at 760 I 1 mmHg
157.1 154.4 151.4 148.6 145.3 142.0 140.2 136.5 134.7 131.8 128.8 126.2 124.9 121.1 117.3 114.5 112.0
0.103 0.118 0.146 0.173 0.202 0.24 1 0.258 0.312 0.348 0.397 0.452 0.504 0.540 0.637 0.756 0.840 0.950
0.411 0.440 0.513 0.568 0.622 0.681 0.705 0.760 0.780 0.814 0.848 0.869 0.882 0.917 0.955 0.973 0.990
0.423 0.455 0.522 0.575 0.617 0.673 0.686 0.746 0.786 0.821 0.850 0.871 0.892 0.922 0.952 0.958 0.992
0.487 0.528 0.591 0.641 0.685 0.73 2 0.747 0.794 0.817 0.843 0.866 0.883 0.874 0.917 0.939 0.955 0.981
Figure 1. Equfflbrlum diagram for toluene-butyl cellosolve at 760 mmHg: (0)experlmental, (-) Wilson equatlon, (- - -) UNIFAC.
&eek Letters activity coefficient Wilson parameter total pressure, mmHg fugacity coefflclent
Y
A 7r
absolute average error in y , is 0.0081. The temperature-independent Wilson parameters are A,2 = 1.3877 A,, = 0.3870 For the UNIFAC method (9) the required parameters are taken from the data of omehling et al. (70). The groups considered are CH, (or CH,), OH, CH20 for butyl cellosolve, and ACH and ACCH, for toluene. The predicted values of y , from UNIFAC are presented in Table 11. The UNIFAC method predicts the vapor composition with an average absolute error of 0.0348. The comparison of the experimental, Wilson, and UNIFAC vapor compositions is given In Figure 1. The system toluene-butyl cellosolve is a typical example as It contains alcohol, ether, aromatic hydrocarbon, and methyl goups, and as such It provides a good test for the a m of the UNIFAC method to predict vapor-liquid equilibria. The higher vakres of vapor composition predicted by this method are apparently due to the use of group interactkin parameters derived from compands contekdngthe alcohol group only or the ether gouponly. I f g o u p b l t e r a c t i o n ~ ~ h a d b e e n e v a l u a t e d fromthedata of a homologue of butyl celbsok, the prediction would have been better.
4
superscripts liquid standard state v vapor phase L S
Subscripts i any component 1 more-volatile component 2 less-volatile component calcd calculated
Literature Cited (1) Ward, S.H. Ph.D. Thds, The Unlvedty of Texas, Austin, TX, 1952. (2) Ravipnured, A.; Venkateswara Reo, K.; Chkanjtvi. C. I-n (2”. Eng. 1977, 19, 29-32. (3) H a m ,J. Q.; O’Connsll. J. P. I n d . Eng. Chem. h c e s s Des. Dev. 1975, 14, 209. (4) Yen, L. C.; Woods, S. S. A I M J . 1908, 12, 95. (5) GmdJlng, J., mate comnunkation. (6) -rF A.; QmehUng, J.; Rat”,P. “Vapor-LiquId EquYibrla Us4g UNIFAC, A boup Contrtbutkn Method”; Elsevkr: Amsterdam,
1977. . is(r5, 57, 18-26. (7) orye, R. v.; ~ausnitz,J. M. I&. ~ n g m. (8) Vmkataswara Rao, K.; Ravlprased,A.; ChiranJM, C. I&n Chem. E**,
PO
R t T V X
Y
vapor pressure of the pure component, mmHg universal gas constant temperature, *C temperature, K molar volume, cm3/mol equtlibrlum liquid composition, mole fraction equilibrium vapor composition, mole fraction
In prw.
(9) Fredendund, A.; Jones, R. L.; Prausnltz,J. M. AIChEJ. 1975, 21, 108649. (10)SkJdAIwgenson, S.; Kobe. B.; t3nehhg, J.; Rasmunsen. P. Ind. Eng. Chem. RocmsDss. &v. 1979, 18, 714-22. W A.; R a w , S. E.; Riddlck, J. A.; Toopa, E. E.. Jr. (11), “Organhc soh”, 2nd ed.; Interscknce: London, 1955. (12) I b a Mdlen. ”Industrhi sdvente”: Reinhold: New York, 1950. Recdved for revbw Muoh 11, 1980. Revised manuscrlpt recdved January 15, 1982. Ampted February 16, 1882.
