HglgPHAS[ EOglUBRIA

ELSEVIER Fluid Phase Equilibria 134 (1997) 151 - 161

Isobaric vapor-liquid equilibrium of binary mixtures of 1-propanol + chlorobenzene and 2-propanol + chlorobenzene

Ana Dejoz, Vicenta Gonzfilez-Alfaro, Francisco J. Llopis, Pablo J. Miguel, M. Isabel Vfizquez *

Departamento de Ingenieria Quimica, Facultad de Quimica, Unil,ersitat de Valencia, Burjassot, 46100 Valencia, Spain

Received 1 November 1996; accepted 23 December 1996

Abstract

Isobaric vapor - l iqu id equilibria were obtained for the system l-propanol + chlorobenzene at 20 and 100 kPa and for the system 2-propanol + chiorobenzene at 100 kPa using a dynamic still. The experimental error in temperature was _+0.1 K, in pressure +0.01 kPa and _+0.1 kPa for the experiments carried out at 20 and 100 kPa, respectively, and in the liquid and vapor mole fraction 0.001. The two systems satisfy the point-to-point thermodynamic consistency test. Both systems show a positive deviation from ideality. The data were well correlated with the Margules, Van Laar, Wilson, NRTL and UNIQUAC equations. © 1997 Elsevier Science B.V.

Keywords: Experimental data; VLE

1. In troduc t ion

Vapor-liquid equilibrium (VLE) data are indispensable in the design of separation processes such as distillation and extractive distillation. Values can be obtained either experimentally or by predictive methods. Among the estimation methods, the most noteworthy are the group contribution methods, especially the UNIFAC method [1]. This model requires a complete and updated experimental VLE data bank in order to fit the group interaction parameters. There is a lack of VLE data for some groups. Gmehling et al. [2] propose different parameters for the different alcohols (primary, secondary and tertiary) by introducing different contribution parameters for different alcohol groups. This would however involve a great increase in the number of required group interaction parameters and the present data base does not allow a fit of these parameters. The present work is part of a project to

* Corresponding author. Fax: + 34 6 386 4898 e-maihisabel.vazquez@uv.es.

0378-3812/97/$17.00 © 1997 Elsevier Science B.V. All rights reserved. PII S0378-3812(97)00028-9

152 A. Dejoz et al. / Fhdd Phase Equilibria 134 (1997) 151-161

determine vapor-liquid equilibrium in mixtures in which one component, at least, is an alcohol. Another functional group for which more experimental data is desirable is the ACC1 group.

Chlorobenzene forms an azeotropic mixture with 1-propanol [3,4]. In this article we report equilibrium data at 20 and 100 kPa for this system to study the influence of the pressure on the azeotropic composition. For the 2-propanol + chlorobenzene system only the equilibrium data at 100 kPa are reported.

2. Experimental

2.1. Chemicals

All components used were purchased from Aldrich Chemie Co. The purity of all chemicals was checked by gas chromatography (GC) and found to be: l-propanol (99.97 mass%), 2-propanol (99.92 mass%) and chlorobenzene (99.99 mass%). They were used without further purification. The water content was small in all chemicals ( < 0.05 mass%, checked by GC). The densities of the pure liquids were measured at 298.15 K using an Anton Paar DMA 55 densimeter. The refractive indexes of the pure liquids were measured at 298.15 K in an Abbe refractometer, Atago 3T. Temperature was controlled to _+0.01 K with a thermostated bath. The accuracies in density and refractive index measurements are +0.01 kg m -3 and _+0.0002, respectively. The experimental values of these properties and the boiling points are given in Table 1 together with those given in Ref. [5].

2.2. Apparatus and procedure

The equilibrium vessel used in this work was an all-glass, dynamic recirculating still described by Walas [6], equipped with a Cottrell pump. The still (Labodest model) manufactured by Fischer Labor und Verfahrenstechnik (Germany) is capable of handling pressures from 0.25 to 400 kPa, and temperatures up to 523.15 K. The Cottrell pump ensures that both liquid and vapor phases are in intimate contact and also in contact with the temperature sensing element. The equilibrium tempera- ture was measured with a digital Fisher thermometer with an accuracy of _+ 0.1 K, and the pressure with a digital manometer with an accuracy of ±0.01 kPa. The temperature probe was calibrated against the ice and steam points of distilled water. The manometer was calibrated against high purity ( > 99.9 mass%) hexane vapor pressures.

In each experiment, the pressure was fixed and the heating and stirring system of the liquid mixture was connected. The still was operated until equilibrium was reached. Equilibrium conditions were assumed when constant temperature and pressure were obtained for 15 min or longer. The experimen-

Table 1 Density, d, refractive index, n, and boiling point, Tb, of the chemicals

Component d(298.15 K) (kg m - 3) n(298.15 K) (D) Tb(100 kPa) (K)

exptl. Ref. [5] exptl. Ref. [5] exptl. Ref. [5]

I-propanol 799.63 799.75 1.3832 1.3837 369.75 369.95 2-propanol 781.21 781.26 1.3750 1.3752 354.85 355.09 chlorobenzene 1101.01 1101.1 1.5218 1.52138 404.05 404.42

A. Dejoz et al. / Fluid Phase Equilibria 134 (1997) 151-161 153

tal error in temperature was _+0.1 K and in pressure _+0.01 and +_0.1 kPa for the experiments carried out at 20 and 100 kPa, respectively. At this time, samples of liquid and condensate were taken for analysis. The sampling was carried out with special syringes that allowed us to take small volume samples in a system under partial vacuum.

Table 2 Vapor pressure p o, Antoine coefficients A, B, and C, and standard deviations (o-) a, of pure components

1-propanol 2-propanol Chlorobenzene

T (K) Pi ° (kPa) T (K) p o (kPa) T (K) pgo (kPa)

303.35 3.82 300.35 6.59 320.55 4.92 306.85 4.82 303.85 8.17 324.65 5.96 310.05 5.82 306.75 9.71 328.35 7.07 312.75 6.86 306.85 9.75 331.35 8.08 316.15 8.31 309.45 11.34 334.15 9.14 319.25 9.91 311.45 12.71 338.45 10.96 322.45 11.85 313.55 14.30 342.55 12.98 325.95 14.21 315.25 15.68 346.35 15.11 329.25 16.83 317.35 17.56 349.35 17.00 332.15 19.46 319.45 19.62 353.55 20.00 334.15 21.51 321.45 21.76 354.05 20.34 335.95 23.51 322.85 23.30 357.95 23.50 338.05 25.99 324.35 25.17 361.05 26.27 340.85 29.67 326.15 27.56 363.75 28.88 343.35 33.33 327.55 29.57 366.85 32.19 346.05 37.59 329.55 32.62 370.15 35.95 348.85 42.64 331.85 36.45 372.65 38.99 351.75 48.41 334.55 41.41 376.55 44.29 354.15 53.72 336.95 46.28 380,05 49.51 356.35 58.97 339.55 52.09 382.95 54.21 358.55 64.62 341.55 56.93 385,95 59.43 360.45 69.85 343.25 61.39 389.25 65.64 362.15 74.80 345.05 66.40 391.25 69.58 363.65 79.42 346.75 71.44 393.85 75.10 365.35 84.97 348.35 76.52 396.25 80.57 366.45 88.69 349.85 81.57 398.35 85.48 367.65 92.93 351.35 86.75 400.15 89.94 368.55 96.20 352.65 91.52 401.35 92.95 369.95 101.37 353.85 96.08 402.65 96.39

354.95 100.46 404.05 100.00 404.55 101.32 404.75 101.87

Component A B C ~ (kPa) 1-propanol 16.0353 3415.56 - 7 0 . 7 3 3 0.045 2-propanol 16.4089 3439.60 - 6 3 . 4 1 7 0.036 chlorobenzene 13.8897 3168.06 - 6 2 . 8 1 9 0.052

" o- = ~ [ po _ p O ( c a l c ) ] 2 / ( N - p ) ; N = number of data points; p = number of parameters.

154 A. Dejo: et a l . / Fluid Phase Equilibria 134 (1997) 151-161

2.3. Analysis

Samples of the liquid and condensed vapor phases were analyzed by using a Hewlett-Packard 5890 S-II gas chromatograph (GC), after calibration with gravimetrically prepared standard solutions. A flame ionization detector was used together with a 60 m, 0.2 mm i.d. fused silica capillary column, SUPELCOWAX 10. The GC response peaks were integrated by using a Hewlett-Packard 3396 integrator. At least two analyses were made of each liquid and each vapor sample. The experimental error in the mole fraction was less than 0.001.

3. Results and discussion

The vapor pressures of the pure components P;" were measured with the same recirculating still. The experimental values, in the range of work temperature, together with the parameters of the Antoine equation:

Bi In(P;°/kPa) = A, (1) (T/K) + C,

and the standard deviation (or), are given in Table 2. Fig. 1 presents a comparison between the experimental values obtained in this work for the three components and those of the literature [5]. As can be seen, our experimental results agree well with those from literature.

The VLE measurements were made at 20 and 100 kPa for the 1-propanol + chlorobenzene system and at 100 kPa for the 2-propanol + chlorobenzene system, and the results are presented in Tables 3-5. The T-x-y diagrams for the two systems are shown in Figs. 2 and 3. Fig. 4 shows a comparison

5.00

g. a¢

o

, .c- 4 . 00

3.00 I ~

2.00

1.00

0 . 0 0 ' ' '

2.00 2.50 3.00 3.50

I/T. 10 3 (K -1 ) 4 .00

Fig. I. Comparison among the experimental vapor pressure values obtained in this work and those from literature for l-propanol ((C)) experimental, (O) literature [5]), 2-propanol (( [] ) experimental, ( • ) literature [5]) and chlorobenzene (( A ) experimental, ( • ) literature [5]).

A. Dejoz et al. / Fluid Phase Equilibria 134 (1997) 151-161 155

Table 3 Vapor-liquid equilibrium data, liquid-phase mole fraction x~, vapor-phase mole fraction y~, temperature T, and activity coefficients "Yi for l-propanol (1)+ chlorobenzene (2) at 20 kPa

xl yl T (K) 71 Y2

0.000 0.000 353.55 0.007 0.108 350.75 0.018 0.224 347.95 0.039 0.373 343.45 0.062 0.449 340.35 0.093 0.508 337.85 0.129 0.545 336.05 0.159 0.570 335.25 0.194 0.599 334.55 0.235 0.608 333.95 0.278 0.621 333.45 0.325 0.634 333.05 0.366 0.649 332.65 0.415 0.657 332.35 0.467 0.666 332.15 0.506 0.675 331.95 0.555 0.689 331.65 0.604 0.701 331.45 0.647 0.716 331.35 0.693 0.733 331.25 0.740 0.754 331.15 0.785 0.777 331.15 0.825 0.805 331.25 0.864 0.834 331.35 0.899 0.866 331.55 0.931 0.901 331.85 0.956 0.933 332.05 0.976 0.961 332.35 0.988 0.979 332.55 1.000 1.000 332.75

6.5607 6.1729 5.7025 5.0022 4.2518 3.5891 3.1591 2.8090 2.4246 2.1453

.9141

.7737

.6062

.4608

.3792

.3049

.2322

.1800 1.1337 1.0970 1.0660 1.0452 1.0289 1.0167 1.0056 1.0048 0.9983 0.9955

0.9970 0.9767 0.9632 0.9831 1.0063 1.0442 1.0574 1.0616 1.1213 1.1743 1.2321 1.2796 1.3730 1.4831 1.5707 1.6863 1.8376 1.9683 2.1371 2.3380 2.5607 2.7426 2.9910 3.2199 3.4611 3.6079 3.8089 3.9414

be tween the exper imenta l values ob ta ined in this work at 100 kPa and those o f the literature for the

1-propanol + ch lo robenzene [4] and the 2 -propanol + ch lo robenzene [7] systems.

F r o m Fig. 2 it can be obse rved that the 1-propanol + ch lo robenzene sys tem shows a m i n i m u m boi l ing azeo t rope and that the azeot ropic point changes with pressure. Table 6 shows a compar i son be tween the azeot ropic data repor ted in the literature for this sys tem and the values obta ined in this

work. F r o m these results it can be conc luded that the mole f ract ion o f 1-propanol in the azeotropic point sl ightly increases with pressure.

The l iquid-phase act ivi ty coeff ic ients o f the c o m p o n e n t s were calcula ted by the equat ion:

yi~biP = x iv i~b¢Pi°exp[ ~'i( P - p i ° ) / R T ] (2)

where x i and yi are the l iquid and vapor mole fract ions in equi l ibr ium; ~b i is the fugaci ty coeff icient ; P is the total pressure; 7~ is the act ivi ty coeff ic ient ; ~bg ~ is the pure c o m p o n e n t fugac i ty coeff ic ient at

156 A. Dejo7~ et al. / Fluid Phase Equilibria 134 (1997) 151-161

Table 4 Vapor-liquid equilibrium data, liquid-phase mole traction x], vapor-phase mole fraction Yl, temperature T, and activity coefficients Yi for 1-propanol (l)+chlorobenzene (2) at 100 kPa

xl Yt T (K) Yl 72

0.000 0.000 404.05 0.012 0.114 400.25 3.2901 0.9882 0.024 0.202 397.45 3.1888 0.9738 0.047 0.311 392.55 2.9884 0.9894 0.074 0.415 388.75 2.8682 0.9649 0.104 0.490 384.95 2.7289 0.9743 0.135 0.537 381.95 2.5537 1.0027 0.170 0.582 379.75 2.3766 1.0086 0.208 0.623 378.05 2.2034 1.0058 0.246 0.644 376.55 2.0332 1.0462 0.289 0.675 375.25 1.9019 1.0552 0.331 0.688 374.45 1.7423 1.1052 0.377 0.713 373.55 1.6387 1.1235 0.426 0.725 372.85 1.5113 1.1955 0.468 0.741 372.35 1.4342 1.2336 0.517 0.752 371.85 1.3412 1.3235 0.562 0.765 371.35 1.2783 1.4072 0.611 0.777 370.95 1.2129 1.5236 0.657 0.790 370.55 1.1634 1.6488 0.702 0.804 370.15 1.1260 1.7908 0.748 0.823 369.85 1.0929 1.9374 0.791 0.840 369.65 1.0632 2.1224 0.832 0.860 369.55 1.0385 2.3188 0.869 0.882 369.45 1.0241 2.5071 0.903 0.907 369.35 1.0166 2.6920 0.932 0.931 369.35 1.0106 2.8655 0.957 0.953 369.45 1.0050 3.0043 0.975 0.972 369.45 1.0051 3.1565 0.987 0.985 369.55 1.0025 3.2338 1.000 1.000 369.75

saturation; P / ' is the pure c o m p o n e n t vapor pressure; t,i is the l iquid mola r vo lume; R is the universal

gas constant ; and T is the absolute temperature. Fugac i ty coeff ic ients ~b~ and d~i ' were calcula ted by means o f the virial equat ion o f state. The

l iquid mola r vo lumes as well as the equa t ion and the parameters to calculate the second virial

coeff ic ients were taken f rom literature [8]. The values o f the activi ty coeff ic ients calcula ted using Eq. (2) are listed in Tables 3 - 5 . It can be obse rved that both sys tems present a posi t ive devia t ion f rom ideality.

The results were tested for t h e r m o d y n a m i c cons i s tency us ing the poin t - to-poin t me thod o f Van Ness et al. [9], modi f ied by Fredens lund et al. [1]. A four -paramete r Legendre po lynomia l was used for the excess Gibbs energy. A c c o r d i n g to Fredens lund et al., the P , T, x, y values are consis tent if

the m e a n absolute devia t ion be tween calcula ted and measured mole fract ions o f c o m p o n e n t 1 in the vapor phase, 8 ( y ) , is less than 0.01. The results o f this test for the b inary sys tems in cons idera t ion are

A. D£joz et al. / Fluid Phase Equilibria 134 (1997) 151 161 157

420

T/K q

400-

380"

i

34O

320 0.0 012 014 016 018 1.0

Xl , Y l

Fig. 2. Vapor-liquid equilibrium of the system l-propanol (1)+ chlorobenzene (2) at 20 and 100 kPa as a function of the mole fraction of component 1. ( O ) Experimental points, (---) splined curves.

420

T/K

4OO

38O

36O

340 i , , i

0.0 02 0 4 0.6 08 1.0 Xl , Yl

Fig. 3. Vapor-liquid equilibrium of the system 2-propanol ( l )+chlorobenzene (2) at 100 kPa as a function o f the mole fraction of component 1. ( O ) Experimental points, (---) splined curves.

158 A. l)£jo: et al. / Fluid Phase Equilibria 134 (1997) 151-161

Table 5 Vapor-l iquid equilibrium data, liquid-phase mole fraction x~, vapor-phase mole fraction y~, temperature T, and activity coefficients Yi for 2-propanol ( l )+ch lo robenzene (2) at 100 kPa

Xl Yl 7" (K) Yl 3'2

0.000 0.000 404.05 0.010 0.136 399.55 2.9333 0.9808 0.019 0.232 395.95 2.9025 0.9725 0.040 0.381 389.25 2.8158 0.9698 0.060 0.474 384.05 2.7342 0.9839 0.089 0.568 378.95 2.6176 0.9758 0.124 0.636 374.25 2.4967 0.9902 0.154 0.678 371.25 2.3757 1.0023 0.182 0.71)3 368.85 2.2722 1.0337 0.222 0.740 366.55 2.131 I 1.0293 0.261 0.764 364.55 2.0136 1.0522 0.313 0.780 363.15 1.8110 1.1036 0.361 0.802 361.95 1.6880 1. I 169 0.410 0.811 360.95 1.5586 I. 1956 0.453 0. 823 360.15 1.4775 1.2410 0.505 0.829 359.45 1.3726 1.3557 0.554 0.848 358.85 1.3078 1.3733 0.607 0. 857 358.25 1.2361 1.4953 0.677 0.873 357.55 I. 1606 1.6570 0.722 0.880 357.05 I. 1179 1.8492 0.77(I 0.891 356.55 1.0836 2.0585 0.814 0.906 356.15 1.0577 2.2358 0.857 0.921 355.85 1.0336 2.4642 0.895 0.936 355.45 1.0222 2.7534 0.935 0.956 355.15 1.0114 3.0805 0.969 0.977 354.95 1.0051 3.4146 1.000 1.000 354.85

06 .

1.0,

0.8.

0 4 .

0.2.

0.0~ 0.0

i i I i

02 0.4 0.6 OB 10

X 1

Yl

Fig. 4. Comparison among the experimental values obtained in this work and those from literature: 1-propanol ( 1 )+ chlorobenzene (2) ( ( O ) experimental, ( 0 ) literature [4]) and 2-propanol ( 1 ) + chlorobenzene (2) (( [] ) experimental, ( I ) literature [7]).

A. Dqjoz et al. / Fluid Phase Equilibria 134 (1997) 151 161 159

Table 6 Azeotropic data of the 1-propanol (1) + chlorobenzene (2) system

P (kPa) x I T (K)

20 " 0.769 331.15 40 b 0.838 347.15

100 " 0.926 369.35 101.325 ~ 0.933 369.05

This work. b Ref. [3]. c Ref. [41.

3(y) = 0.0048 and 3(y) = 0.0050 for the 1-propanol + chlorobenzene system at 20 and 100 kPa, respectively, and 3(y) = 0.0038 for the 2-propanol + chlorobenzene system at 100 kPa. These results indicate that the experimental data for the two systems are thermodynamically consistent.

The activity coefficients were correlated with the Margules, Van Laar, Wilson, NRTL and UNIQUAC equations [10]. For fitting the binary parameters the following objective function was used:

f = ~ ( ")/I - - "~l(calc) -~- ~ ")/2 - - ~/2(calc) (3) Yl T2

For both systems all the models yield similar deviations between the experimental and calculated vapor compositions and temperatures. The parameters and average deviations obtained for these

Table 7 Parameters and deviat ions between calculated and experimental vapor phase mole fractions and temperatures

P (kPa) Model AI2 A21 al2 ~ (y ) ~ ~(T) b

20

100

100

1 -propanol (1) + chlorobenzene (2) Margules 1.8520 c 1.3392 c 0.0068 0.231 Van Laar 1.8919 c 1.3556 " 0.0051 0.207 Wilson 1260.317 d 207.720 d 0.0041 0.106 NRTL 452.623 d 1010.203 d 0.48 0.0036 0.134 U N I Q U A C - 142.048 ,L 632.650 d 0.0050 0.207 Margules 1.2049 1.2242 0.0074 0.146 Van Laar 1.2050 1.2241 0.0074 0.146 Wilson 778.579 327.836 0.0089 0.127 NRTL 504.633 577.951 0.458 0.0090 0.141 U N I Q U A C - 14.092 336.309 0.0088 0.135 2-propanol (1) + chlorobenzene (2) Margules 1.1067 1.3207 0.0043 0.227 Van Laar 1.1122 1.3282 0.0043 0.240 Wilson 656.404 417.421 0.0057 0.264 NRTL 607.845 420.096 0.402 0.0056 0.235 U N I Q U A C 100.659 194.557 0.0056 0.199

a(),)= El), v ( c a l c ) / N . b ~ ( T ) = ~]T -- T(calc)] /N; N = number of data points. " Dimensionless . d Cal tool i.

160 A. Dejoz et al. / Fluid Phase Equilibria 134 (1997) 151 161

.'~ 0.5

I

0.4

0.3

0.2

0.1

0.0

-0.1 O0 0.2 014 016 018 1.0

xl

Fig. 5. Comparison among the experimental values obtained in this work (l-propanol (1)+ chlorobenzene (2) at 20 kPa (z~) and at 100 kPa ( 0 ) and 2-propanol (1)+ chlorobenzene (2) at 100 kPa ([])) and those calculated using the Wilson equation (---).

models are reported in Table 7. Fig. 5 presents a comparison between the experimental values obtained in this work and those calculated using the Wilson equation. It can be observed that this equation fits the VLE data obtained in this work well.

4. List of symbols

P C" R T

U i

X i

Yi

Yi

pressure pure component vapor pressure universal gas constant temperature liquid molar volume liquid mole fraction vapor mole fraction fugacity coefficient pure component fugacity coefficient at saturation activity coefficient

Acknowledgements

This work has been supported by the Generalitat Valenciana (Grant GV-1006 /93 ) .

A. Dejoz et al. / Fluid Phase Equilibria 134 (1997) 151-161 161

References

[1] A. Fredenslund, J. Gmehling, P. Rasmussen, Vapor-Liquid Equilibria Using UNIFAC, Elsevier, Amsterdam, 1977. [2] J. Gmehling, J. Li, M. Schiller, A modified UNIFAC model. Present parameter matrix and results for different

thermodynamic properties, Ind Eng. Chem. Res. 32 (1993) 178. [3] S.R.M. Ellis, C. McDermott, J.C.L. Williams, Proc. of the Int. Symp. on Dist., Inst. Chem. Eng., London, 1960. [4] K. Venkateswara Rao, A. Ravi Prasad, C. Chiranjivi, Isobaric vapor-liquid equilibrium of binary mixtures of

l-propanol + chlorobenzene and l-butanol + chlorobenzene, J. Chem. Eng. Data 22 (1) (1977) 44. [5] TRC Thermodynamic Tables Hydrocarbons, Thermodynamic Research Center, The Texas A and M University System,

College Station, TX, 1996. [6] S.M. Walas, Phase Equilibria in Chemical Engineering, Butterworth, London, 1985. [7] M. Narasimha Rao, B.V. Subba Rao, Isobaric vapour-liquid equilibrium of the binary systems isobutanol-chlorobe-

nzene and isopropanol-chlorobenzene, Ind. J. Technol. 14 (1976) 604. [8] T.E. Daubert, R.P. Danner (Eds.), Physical and Thermodynamic Properties of Pure Chemicals: Data Compilation,

Taylor and Francis, Washington, 1995. [9] H.C. Van Ness, S.M. Byer, R.E. Gibbs, Vapor-liquid equilibrium, part 1. An appraisal of data reduction methods,

AIChE J. 19 (1973) 238. [10] J. Gmehling, U. Onken (Eds.), Vapor-Liquid Equilibrium Data Collection, Chemistry Data Series, DECHEMA,

Frankfurt/Main, 1977.