Article pubs.acs.org/jced
Liquid−Liquid Equilibria for the Ternary System Water + Benzyl Alcohol + Methylbenzene at (303.2 to 343.2) K Hui Wang,† Qinbo Wang,*,† Zhenhua Xiong,‡ and Chuxiong Chen‡ †
Department of Chemical Engineering, Hunan University, Changsha, 410082 Hunan P. R. China Zhejiang Shuyang Chemical Co. Ltd., Quzhou, 324002 Zhejiang P. R. China
‡
S Supporting Information *
ABSTRACT: Liquid−liquid equilibrium (LLE) data for the ternary system water + benzyl alcohol + methylbenzene were measured at (303.2 to 343.2) K under atmospheric pressure. The Othmer−Tobias and the Hand correlations were used to check the reliability of the experimental LLE data. The distribution coefficient and separation factor were used to investigate the ability of water to extract benzyl alcohol from methylbenzene. The results show that the distribution coefficient of benzyl alcohol increases with the increasing mass fraction of water in the aqueous phase. The experimental data were correlated by both the nonrandom two-liquid (NRTL) and the universal quasichemical (UNIQUAC) activity coefficient models. The relevant model interaction parameters were regressed by data fitting. The model calculated results show good agreement with the measured data. The obtained interaction parameters can be used in the calculation of LLE for the ternary system water + benzyl alcohol + methylbenzene as well as for the design and optimization of the related separation process.
1. INTRODUCTION Benzyl alcohol is an important fine chemical. It is widely used in the field of food, medicine, daily chemicals, and so on. Traditionally, it is produced by the hydrolysis process of benzyl chloride, which would simultaneously produce a large amount of acidic wasting water and cause serious environmental problems. Though there are also some studies about the air oxidation of methylbenzene to produce benzyl alcohol, this method is still less than ideal because of the poor selectivity. In recent years, some researchers have found a green way to oxidize methylbenzene.1−3 In this way, methylbenzene is oxidized by hydrogen peroxide, and this method is cleaner, safer, and more cost-effective compared with the traditional ways. These existing studies provide a new idea to produce benzyl alcohol. Hydrogen peroxide is an excellent oxidant because of its high oxygen content, and water is the sole theoretical coproduct. In this oxidation system, the reaction mixture would split into two liquid phases due to the existence of water. It is designed to separate benzyl alcohol from the liquid mixtures after the oxidation. It is therefore of greatest importance to measure the liquid−liquid equilibrium (LLE) data of the ternary system water + benzyl alcohol + methylbenzene at different temperatures and © 2014 American Chemical Society
different compositions. Until now, liquid−liquid equilibria for binary mixtures of water + methylbenzene4−18 and water + benzyl alcohol19−23 could be found, but except for the work of Skrzecz,24 no publication or reports on the ternary system water + benzyl alcohol + methylbenzene are available. Furthermore, in the work of Skrzecz, the vapor−liquid−liquid equilibrium (VLLE) data for the ternary system water + benzyl alcohol + methylbenzene were only measured at 293.2 K and (362.2 ± 0.5) under atmospheric pressure. The experimental data was difficult to extrapolate to other temperatures. In this work, the LLE data for the ternary system water + benzyl alcohol + methylbenzene were measured at (303.2 to 343.2) K under atmospheric pressure. The reliability of the experimental LLE data was confirmed according to the Othmer− Tobias and the Hand correlations. The experimental data were correlated by the NRTL (nonrandom two-liquid) activity coefficient model25 and UNIQUAC (universal quasichemical activity coefficient) model.26 The relevant interaction parameters Received: February 26, 2014 Accepted: May 10, 2014 Published: May 20, 2014 2045
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Fischer titrator (Mettler-Toledo V20). The analytic procedure is described in detail elsewhere.28 For the aqueous phase, the concentrations of benzyl alcohol and methylbenzene were measured, and the concentration of water was determined by the normalized calculation. For the organic phase, the concentrations of benzyl alcohol and water were measured, and the concentration of methylbenzene was determined by the normalized calculation. To verify the reliability and reproducibility of the GC analysis method, five methylbenzene and benzyl alcohol solutions of known concentrations were analyzed. For each solution, the composition was measured at least three times. The standard uncertainty of benzyl alcohol in mass fraction was determined to be 0.0010, and that for methylbenzene was determined to be 0.0014. To verify the reliability and reproducibility of the water concentration determination method, five benzyl alcohol and water solutions of known concentration were analyzed, too. Similarly, each solution was measured at least three times. The standard uncertainty of water in mass fraction was determined to be 0.0008.
are expected to be regressed with the experimental data. The obtained interaction parameters might be used in the calculation of LLE for the ternary system water + benzyl alcohol + methylbenzene as well as for the design and optimization of the related separation process which is an ongoing part of our work.
2. EXPERIMENTAL SECTION 2.1. Materials. The materials used include methylbenzene, benzyl alcohol, and 1,4-dimethylbenzene, which were obtained from Xilong Chemical Co. and had a declared purity of 0.990 in mass fraction. Gas chromatography was used to check the purity of these chemicals. Purified water manufactured by Hangzhou Wahaha Group Co. was obtained from the supermarket (596 mL each bottle). All of the chemicals used in the experiments were used without further purified. The suppliers and the mass fraction of the used chemical reagents are shown in Table 1. Table 1. Suppliers and Mass Fractions of the Chemical Reagent component methylbenzene benzyl alcohol 1,4-dimethylbenzene water a
suppliers Chemical Reagent Co. Xilong Chemical Co. Xilong Chemical Co. Hangzhou Wahaha Group Co.
mass fraction
analysis method
>0.990 >0.990 >0.996 >0.999
GCa GCa GCa
3. RESULTS AND DISCUSSION 3.1. Data Reliability Checking. The reliability and consistency of the experimental LLE data can be tested by the Othmer−Tobias29 and the Hand correlations.30The equations are shown as eq 1 and eq 2:
Gas chromatograph.
2.2. Apparatus and Procedures. The experimental apparatus and sampling methods used in this work was described in detail by Wang et al.27 and Shen.28 Briefly, in each experiment, a given amount of water, methylbenzene, and benzyl alcohol were added into a 100 mL round-bottom glass bottle and then heated the bottle to the desired temperature within 0.1 K by putting it in a thermostatic water bath. To prevent the evaporation of solvent, the bottle was sealed by a rubber stopper. After reaching the desired temperature, the mixture was stirred about 3 h to accelerate the partition of benzyl alcohol between methylbenzene and water. Then the mixture was left undisturbed for 24 h for phase equilibrium. To verify the attainment of LLE, the upper and lower liquid phases were sampled once an hour, and then the phase composition was determined. Experimental results show that 3 h was enough for benzyl alcohol + methylbenzene + water to reach LLE, because repetitive measurements during the following several hours indicated the results were reproducible with 3 %. A series of LLE measurements were carried out by changing the temperatures and the compositions of the mixture. The uncertainty of experimental temperature was 0.1 K, and the uncertainty of balance used in this work is 0.0001 g. 2.3. Analysis. In each measurement, about 1.0 g of the solution was sampled for the aqueous phase, and about 0.2 g of the solution was sampled for the organic phase. The concentrations of benzyl alcohol and methylbenzene were analyzed by the gas chromatograph (GC-1690) equipped with a flame ionization detector (FID) produced by KeXiao Chemical Instrument Co. Ltd. The GC column was a capillary column (30m × 0.32 mm × 0.50 μm; stationary phase, AT SE-54). The internal standard method was used, and 1,4-dimethylbenzene was chosen as the internal standard substance. The concentration of water was determined by using a compact volumetric Karl
⎛ 1 − W33 ⎞ ⎛ 1 − W11 ⎞ ln⎜ ⎟ ⎟ = A + B ln⎜ ⎝ W11 ⎠ ⎝ W33 ⎠
(1)
⎛W ⎞ ⎛W ⎞ ln⎜ 21 ⎟ = M + N ln⎜ 23 ⎟ ⎝ W11 ⎠ ⎝ W33 ⎠
(2)
In eq 1, A and B are constants of the Othmer−Tobias correlation, respectively. W11 is the mass fraction of water in the water-rich phase, and W33 is the mass fraction of benzyl alcohol in the benzyl alcohol-rich phase. In eq 2, M and N are constants of the Hand correlation, respectively. W11 and W21 are the mass fractions of water in the aqueous phase and the organic phase, and W23 is and W33 are the mass fractions of benzyl alcohol in the aqueous phase and the organic phase, respectively. The parameters in Othmer−Tobias and the Hand equations are linear-regressed by fitting the experimental data with eq 1 and eq 2. The results are listed in Tables 2 and 3. The Othmer− Tobias plot (Figure 1) and Hand plot (Figure 2) were also used to evaluate the thermodynamic consistency of the experimental data. The results indicated that the linear correlation coefficients, Table 2. Constants of the Othmer−Tobias Equation for the Water (1) + Benzyl Alcohol (2) + Methylbenzene (3) System at (303.2 to 343.2) Ka Othmer−Tobias T/K
A
B
R2b
303.2 313.2 323.2 333.2 343.2
−3.501 ± 0.009 −3.434 ± 0.007 −3.407 ± 0.009 −3.333 ± 0.010 −3.352 ± 0.010
−0.250 ± 0.010 −0.259 ± 0.007 −0.258 ± 0.010 −0.283 ± 0.010 −0.245 ± 0.011
0.987 ± 0.007 0.993 ± 0.003 0.989 ± 0.006 0.989 ± 0.008 0.994 ± 0.008
a
Standard uncertainty u is u(T) = 0.1 K. bR2 is the linear correlation coefficient. 2046
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were also compared with the literature data of the binary mixtures which were mentioned before. The results are shown in Figures 5 and 6. We found that the obtained experimental data have no important deviations with the literature data. The experimental results given in Table 4 indicate that water could be regarded as insoluble with methylbenzene. The solubility of benzyl alcohol in the aqueous phase is greater than methylbenzene in the aqueous phase. The result given in Figures 3 and 4 shows that the mutual solubility of water and methylbenzene increases slightly with the increase of benzyl alcohol’s mass fraction at settled temperature. Within the temperature range of the measurements, the experimental data shows that the mutual solubility of the mixtures slightly changed but not obviously. The ability of the solvent water to extract benzyl alcohol from methylbenzene could be demonstrated by the separation factor S and distribution coefficients k1 and k2. These parameters are defined as eq 3 to 5:
Table 3. Constants of the Hand Equation for the Water (1) + Benzyl Alcohol (2) + Methylbenzene (3) System at (303.2 to 343.2) Ka Hand T/K
M
N
R2b
303.2 313.2 323.2 333.2 343.2
−10.02 ± 0.374 −10.75 ± 0.295 −8.886 ± 0.382 −10.30 ± 0.428 −8.464 ± 0.372
2.297 ± 0.136 2.647 ± 0.109 2.021 ± 0.143 2.630 ± 0.165 1.969 ± 0.143
0.972 ± 0.164 0.986 ± 0.075 0.961 ± 0.168 0.969 ± 0.205 0.992 ± 0.167
a
Standard uncertainty u is u(T) = 0.1 K. bR2 is the linear correlation coefficient.
Figure 1. Othmer−Tobias plots of the ternary water (1) + benzyl alcohol (2) + methylbenzene (3) system at different temperatures: ■, 303.2 K; ▲, 313.2 K; □, 323.2 K; ○, 333.2 K; ◇, 343.2 K. W11 is the mass fraction of water in the aqueous phase, and W33 is the mass fraction of benzyl alcohol in the organic phase.
S=
k2 k1
(3)
k1 =
w31 w33
(4)
k2 =
w21 w23
(5)
where k 1 and k 2 are the distribution coefficients of methylbenzene and benzyl alcohol between organic and aqueous phases, respectively; w31 and w33 are the mass fractions of methylbenzene in aqueous and organic phases, respectively;w21 and w23 are the mass fractions of benzyl alcohol in aqueous and organic phases, respectively. The separation factors and distribution coefficients at different temperatures are summarized in Table 5. The plots for the solubility and distribution coefficient of benzyl alcohol are showed in Figures 7 and 8. It can be found from the plots that there is no obviously influence of temperature on the distribution coefficient at lower amounts of water. However, at higher amounts of water, a higher distribution coefficient is achieved. 3.3. Correlation of Experimental Data. The activities of each component i in the two coexistent liquid phases of a system at equilibrium might be regarded as equal, and the mole fractions xIi and xIIi of LLE phases can be determined using eqs 6 to 9: xi =
Figure 2. Hand plots of the ternary water (1) + benzyl alcohol (2) + methylbenzene (3) system at different temperatures: ■, 303.2 K; ▲,313.2 K; □, 323.2 K; ○, 333.2 K; ◇, 343.2 K. W11 and W21 are the mass fractions of water in the aqueous phase and in the organic phase, respectively. W23 and W33 are the mass fractions of benzyl alcohol in the aqueous phase and in the organic phase, respectively.
R2, were all close to 1, which shows that the experimental data was highly consistent. It verified that the experimental LLE data were reliable. 3.2. Tie-Lines, Distribution Coefficients, and Separation Factor. The measured LLE data of the ternary system of water (1) + benzyl alcohol (2) + methylbenzene (3) at (303.2 to 343.2) K are summarized in Table 4, and the experimental deviations in the measurement are listed in Table A, which is given as Supporting Information. The diagrams for the ternary system at (303.2 to 343.2) K are supplied in Figures 3 and 4. All concentrations are given in mass fraction. The experimental data
wi /Mi 3 ∑i = 1 wi /Mi
(6)
γi IxiI = γi IIxiII
(7)
∑ xiI = 1
(8)
∑ xiII = 1
(9)
where, γIi and γIIi are the activity coefficients of component i in the aqueous phase and organic phase. The key to solve the equations is to calculate the activity coefficients. As UNIFAC parameters are available for each group constituting selected molecules, maybe the UNIFAC activity coefficient model is a good choice to predict the LLE of water (1) + benzyl alcohol (2) + methylbenzene (3). Thus, the UNIFAC model was used as a try to predict the studied LLE system. The predicted LLE results at 303.2 K by the UNIFAC model are 2047
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Table 4. Experimental Liquid−Liquid Equilibrium Data for theb System Water (1) + Benzyl Alcohol (2) + Methylbenzene (3) at (303.2 to 343.2) K and Pressure p = 101.3 kPaa aqueous phase
aqueous phase
organic phase
w1
w2
0.9969 0.9833 0.9781 0.9769 0.9741 0.9712 0.9701 0.9683 0.9666 0.9656 0.9649 0.9552
0.0000 0.0152 0.0194 0.0212 0.0242 0.0266 0.0282 0.0301 0.0321 0.0332 0.0343 0.0448
0.9958 0.9815 0.9778 0.9751 0.9732 0.9708 0.9683 0.9653 0.9647 0.9636 0.9622 0.9529
0.0000 0.0154 0.0196 0.0226 0.0250 0.0275 0.0301 0.0325 0.0341 0.0353 0.0368 0.0471
0.9942 0.9814 0.9778 0.9736 0.9728 0.9704 0.9671 0.9660
0.0000 0.0157 0.0196 0.0241 0.0252 0.0276 0.0306 0.0322
w3 T = 303.2 0.0031 0.0015 0.0025 0.0019 0.0017 0.0022 0.0017 0.0016 0.0013 0.0012 0.0008 0.0000 T = 313.2 0.0042 0.0031 0.0026 0.0023 0.0018 0.0017 0.0016 0.0022 0.0012 0.0011 0.0010 0.0000 T = 323.2 0.0058 0.0029 0.0026 0.0023 0.0020 0.0020 0.0023 0.0018
w1 K 0.0013 0.0044 0.0084 0.0153 0.0204 0.0264 0.0329 0.0388 0.0430 0.0474 0.0520 0.1027 K 0.0014 0.0048 0.0105 0.0171 0.0224 0.0285 0.0338 0.0406 0.0447 0.0500 0.0564 0.1056 K 0.0022 0.0066 0.0142 0.0180 0.0262 0.0311 0.0357 0.0434
w3
w1
w2
0.0000 0.1042 0.2027 0.2963 0.3738 0.4508 0.5167 0.5742 0.6216 0.6732 0.7054 0.8973
0.9987 0.8914 0.7889 0.6884 0.6058 0.5228 0.4504 0.3870 0.3354 0.2794 0.2426 0.0000
0.9631 0.9622 0.9613 0.9521
0.0352 0.0363 0.0374 0.0479
0.0000 0.1224 0.1946 0.2863 0.3697 0.4199 0.5157 0.5712 0.6184 0.6612 0.7019 0.8944
0.9986 0.8728 0.7949 0.6966 0.6079 0.5516 0.4505 0.3882 0.3369 0.2888 0.2417 0.0000
0.9935 0.9802 0.9777 0.9734 0.9711 0.9681 0.9649 0.9618 0.9594 0.9583 0.9577 0.9515
0.0000 0.0169 0.0198 0.0244 0.0269 0.0300 0.0340 0.0367 0.0388 0.0399 0.0406 0.0485
0.0000 0.1005 0.2021 0.2858 0.3739 0.4432 0.5103 0.5538
0.9978 0.8929 0.7837 0.6962 0.5999 0.5257 0.4540 0.4028
0.9914 0.9799 0.9760 0.9715 0.9697 0.9674 0.9660 0.9639 0.9615 0.9598 0.9554 0.9499
0.0000 0.0172 0.0214 0.0259 0.0280 0.0304 0.0329 0.0341 0.0366 0.0384 0.0429 0.0501
ln γi =
xjGij 3 j = 1 ∑k = 1 Gkjxk
∑
3 ⎛ ∑ xτ G ⎞ ⎜τij − k = 1 k kj kj ⎟ 3 ⎜ ∑k = 1 Gkjxk ⎟⎠ ⎝
T = 323.2 0.0017 0.0015 0.0013 0.0000 T = 333.2 0.0065 0.0029 0.0025 0.0022 0.0020 0.0019 0.0011 0.0015 0.0018 0.0018 0.0017 0.0000 T = 343.2 0.0086 0.0029 0.0026 0.0026 0.0023 0.0022 0.0011 0.0020 0.0019 0.0018 0.0017 0.0000
w1 K 0.0472 0.0529 0.0596 0.1128 K 0.0025 0.0044 0.0115 0.0176 0.0282 0.0321 0.0392 0.0437 0.0534 0.0610 0.0675 0.1250 K 0.0050 0.0076 0.0178 0.0247 0.0300 0.0368 0.0461 0.0482 0.0552 0.0601 0.0686 0.1411
w2
w3
0.6067 0.6559 0.7011 0.8872
0.3461 0.2912 0.2393 0.0000
0.0000 0.1019 0.1928 0.2846 0.3727 0.4393 0.5172 0.5683 0.6238 0.6572 0.6992 0.8750
0.9975 0.8937 0.7957 0.6978 0.5991 0.5286 0.4436 0.3880 0.3228 0.2818 0.2333 0.0000
0.0000 0.1044 0.2066 0.2976 0.3788 0.4508 0.5305 0.5727 0.6336 0.6766 0.6940 0.8589
0.9950 0.8880 0.7756 0.6777 0.5912 0.5124 0.4234 0.3791 0.3112 0.2633 0.2374 0.0000
Standard uncertainties u are u(T) = 0.1 K, ur(p) = 0.05, u(x1) = 0.0008, u(x2) = 0.0010, and u(x3) = 0.0014.
τij = aij +
bij (11)
T
Gij = exp( −αijτij)
αij = αji ,
(12)
τij ≠ τji ,
τii = 0
(13)
where T is the absolute temperature, K. aij and bij are the NRTL binary interaction parameters. The activity coefficient equations for the UNIQUAC model used in this work are ln γi = ln
3
+
w3
a
plotted in Figure 9. For comparison, the experimental LLE data at 303.2 K are also shown in Figure 9. All concentrations are given in mole fraction. It can be seen that apparent deviations appears, which indicate the existing UNIFAC model parameters might be unsuitable for this ternary system. The NRTL and the UNIQUAC models could also be used to correlate the experimental data and could be extrapolated to a wider temperature range. Therefore, the obtained experimental data were correlated by both the NRTL and the UNIQUAC models in this work. The experimental data can be used to determine the interaction parameters between water, benzyl alcohol, and methylbenzene by data fitting. The NRTL activity coefficient equations used in this work are 3 ∑ j = 1 τjiGjixj 3 ∑k = 1 Gkixk
organic phase
w2
ψi xi
+
3 ψ 3 θ z qi ln i + li − i ∑ xjl j − qi ln(∑ θτ j ji) xi j = 1 2 ψi j=1 3
θτ j kj 3 j = 1 ∑k = 1 θkτkj
+ qi − qi∑
·
lj =
(10) 2048
⎛Z⎞ ⎜ ⎟(r − q ) − (r − 1) j j ⎝2⎠ j
(14)
(15)
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Figure 3. LLE of the ternary water (1) + benzyl alcohol (2) + methylbenzene (3) system at different temperatures: ●---●, experimental data tie line; □- -□, correlated data tie line using the NRTL model. wi is the mass fraction of component i in water (1) + benzyl alcohol (2) + methylbenzene (3) solvent mixtures.
ψi =
xiri 3 ∑i = 1 xiri
(16)
θi =
xiqi 3 ∑i = 1 xiqi
(17)
⎛ bij ⎞ τij = exp⎜aij + ⎟ T⎠ ⎝
f minsearch in the optimization toolbox of Matlab (Matwork, MA) uses the Nelder−Mead Simplex approach and can be employed for the minimization of the objective function, which is the corresponding relative-mean-standard deviation (RMSD) between the experimental and the correlated mole fractions defined as 1 RMSD = N
(18)
Here ψi and θi represent the volume fraction and the area fraction. aij and bij are UNIQUAC model parameters. The pure component structural parameters (r and q) are listed in Table 6. Using NRTL model and UNIQUAC model, the experimental data were correlated, and the model parameters were optimized. The optimum algorithm applied in the parameter estimation program was the Nelder−Mead Simplex approach.31 Function
⎛ x exp − x cal ⎞2 ijkt ijkt ∑ ∑ ∑ ∑ ⎜⎜ exp ·100⎟⎟ xijkt ⎠ t k j i ⎝
(19)
cal where N is the total number of tie lines, xexp ijkt and xijkt are the experimental and calculated mole fractions, and subscripts i, j, k, and t denote the component, phase, tie-line, and temperature, respectively. The regressed NRTL binary interaction parameters aij and bij, along with the RMSD are shown in Table 7. The
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Figure 4. LLE of the ternary water (1) + benzyl alcohol (2) + methylbenzene (3) system at different temperatures: ●---●, experimental data tie line; □- -□, correlated data tie line using the UNIQUAC model. wi is the mass fraction of component i in water (1) + benzyl alcohol (2) + methylbenzene (3) solvent mixtures.
In the work of Skrzecz et al.,24 most of the VLLE data points for the ternary system water + benzyl alcohol + methylbenzene were measured at 293.2 K and (362.2 ± 0.5) K under atmospheric pressure. To verify the reliability of the regressed NRTL and UNIQUAC model parameters and evaluate the precision of model extrapolation, we mathematically predicted the LLE data at 362.2 K by using the obtained NRTL model parameters as an illustration. The predicted results were scattered in Figure 10. It can be seen that the predicted results have no apparent deviations with the experimental liquid−liquid data reported by Skrzecz et al.24 It indicates the obtained NRTL parameters were predictable and could be extrapolated to a wider temperature range. As the UNIQUAC method is better than the NRTL method for this system, it could be inferred that the UNIQUAC parameters are predictable, too.
regressed UNIQUAC binary interaction parameters aij and bij, along with the RMSD are shown in Table 8. By using the regressed model parameters, the LLE data under the experimental conditions could be simulated, and the correlated results were also given in Figures 3 and 4 for comparison. As can be seen, the experimental data agree well with the calculated data. Further, from the RMSD results, the predicted results by the UNIQUAC method is slightly better in agreement with the calculated data than that of the NRTL method. 3.4. Model Verification. In this work, LLE data for the ternary system water + benzyl alcohol + methylbenzene have been measured at (303.2 to 343.2) K under atmospheric pressure. The NRTL and UNIQUAC model parameters listed in Tables 7 and 8 were regressed at (303.2 to 343.2) K. 2050
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Figure 7. Mass fraction of benzyl alcohol in the borganic phase versus its mass fraction in the aqueous phase at different temperatures: ■, 303.2 K; ▲, 313.2 K; □, 323.2 K; ○, 333.2 K; ◇, 343.2 K. W21 and W23 are the mass fractions of benzyl alcohol in the aqueous phase and in the organic phase, respectively.
Figure 5. Comparisons between experimental solubility of methylbenzene in the organic phase with that reported in literature. ●, experimental data; □, literature data from Stephenson;6 ○, literature data from Chen and Wanger;8 △, literature data from Jou and Mather;12 ▽, literature data from Marche et al.;14 ◇, literature data from Neely et al.;16 ⬡, literature data from Brown et al.;10 ⬠, literature data from Miller and Hawthorne.11
Figure 8. Distribution coefficients of benzyl alcohol versus the mass fraction of water in the aqueous phase at different temperatures: ■, 303.2 K; ▲, 313.2 K; □, 323.2 K; ○, 333.2 K; ◇, 343.2 K. W11 is the mass fraction of water in aqueous phase, and k2 is the distribution coefficient of benzyl alcohol. Figure 6. Comparisons between experimental solubility of benzyl alcohol in the aqueous phase with that reported in literature. ●, experimental data; □, literature data from Stephenson and Stuart;19 ○, literature data from Solimo and Gramajo de Doz;21 △, literature data from Banerjee.23
+ methylbenzene was regressed.17 Even in the order of magnitude, a great difference was found in the model parameters determined in our work and that in Saien’s work. However, from the calculated Gij listed in Table B in the Supporting Information, they gave the same order of magnitude, which indicated that the two sets of NRTL model parameters were suitable for the binary water + methylbenzene system. It might be due to the nonuniqueness of the parameters during the data-fitting process.
Saien et al. measured the LLE for ternary system water + acetic acid + methylbenzene and correlated the experimental results by the NRTL model. The NRTL model parameters between water
Table 5. Distribution Coefficients k and Separation Factors S of Benzyl Alcohol at Different Temperaturesa T = 303.2 K
a
T = 313.2 K
T = 323.2 K
T = 333.2 K
T = 343.2 K
k
S
k
S
k
S
k
S
k
S
0.146 0.096 0.072 0.065 0.059 0.055 0.052 0.052 0.049 0.049
86.69 29.04 25.92 23.07 13.41 14.46 12.68 13.32 11.48 14.75
0.126 0.101 0.079 0.068 0.065 0.058 0.057 0.055 0.053 0.052
34.32 30.79 23.91 22.84 21.25 15.46 10.04 15.48 14.02 11.52
0.156 0.097 0.084 0.067 0.062 0.060 0.058 0.058 0.055 0.053
48.10 29.23 25.52 20.22 17.23 11.84 12.33 11.81 10.74 9.82
0.166 0.102 0.086 0.072 0.068 0.066 0.065 0.062 0.061 0.058
52.94 32.52 27.18 21.62 19.00 26.51 16.70 11.15 9.50 7.97
0.165 0.104 0.087 0.074 0.067 0.062 0.060 0.058 0.057 0.062
50.45 30.90 22.68 19.00 15.71 23.87 11.29 9.46 8.30 8.63
Standard uncertainty u is u(T) = 0.1 K. 2051
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Figure 9. Comparisons between experimental data and calculated data by the UNIFAC model for the ternary system of water (1) + benzyl alcohol (2) + methylbenzene (3) at 303.2 K. ○- - -○, experimental data tie line; □- - -□, calculated data tie line. xi is the mole fraction of component i in the water (1) + benzyl alcohol (2) + methylbenzene (3) solvent mixtures.
Figure 10. Correlated LLE data and literature data for the ternary water (1) + benzyl alcohol (2) + methylbenzene (3) system at 101.3 kPa: ■---■, literature data tie line; □- - -□, correlated data tie line using the NRTL model. wi is the mass fraction of component i in water (1) + benzyl alcohol (2) + methylbenzene (3) solvent mixtures.
Table 6. r and q Values of the Pure Compounds for UNIQUAC Model
by NRTL and UNIQUAC methods show good consistency with the measured data. From the result, it was seen that the UNIQUAC method is better than the NRTL method. The obtained interaction parameters might be used in the calculation of LLE for the ternary system water + benzyl alcohol + methylbenzene as well as for the design and optimization of the related separation process.
component
r
q
water methylbenzene benzyl alcohol
0.9200 3.9228 4.0217
1.4000 2.9700 3.3220
■
Table 7. Optimized Temperature-Independent Binary Interaction Parameters in the NRTL Model for the Ternary Water (1) + Benzyl Alcohol (2) + Methylbenzene (3) System at (303.2 to 343.2) K i−j
αij
aij
bij
aji
bji
RMSD
1−2 1−3 2−3
0.2 0.2 0.2
0.43 5.73 0.81
2931.5 536.51 −1681.97
0.32 7.02 −1.22
2863.3 2444.60 6689.80
0.11 %
ASSOCIATED CONTENT
* Supporting Information S
Tables A and B. This material is available free of charge via the Internet at http://pubs.acs.org.
■
AUTHOR INFORMATION
Corresponding Author
*E-mail:
[email protected]. Funding
The project was granted financial support from Key S&T Special Project of Zhejiang Province (2012C13007-2) and the Fundamental Research Funds for the Central Universities.
Table 8. Optimized Temperature-Independent Binary Interaction Parameters for the UNIQUAC Model for the Ternary Water (1) + Benzyl Alcohol (2) + Methylbenzene (3) System at (303.2 to 343.2) K i−j
aij
bij
aji
bji
RMSD
1−2 1−3 2−3
−2.93 −0.64 −1.89
893.12 −45.83 792.36
2.07 1.56 5.03
−715.68 −1291.90 −2018.90
0.09 %
Notes
The authors declare no competing financial interest.
■
REFERENCES
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4. CONCLUSIONS Liquid−liquid equilibrium (LLE) data for the ternary water + benzyl alcohol + methylbenzene system have been measured at (303.2 to 343.2) K under atmospheric pressure. The reliability of the experimental LLE data has been checked according to the Othmer−Tobias and the Hand correlations. The distribution coefficient and separation factor were discussed. The experimental data were correlated by the NRTL and UNIQUAC activity coefficient models. The relevant interaction parameters were regressed with the experimental data. The predicted values 2052
dx.doi.org/10.1021/je500195p | J. Chem. Eng. Data 2014, 59, 2045−2053
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dx.doi.org/10.1021/je500195p | J. Chem. Eng. Data 2014, 59, 2045−2053
