Experimental Measurement and Modeling of VaporâLiquid

Article pubs.acs.org/jced

Experimental Measurement and Modeling of Vapor−Liquid Equilibrium for the Ternary System Water + Acetonitrile + Ethylene Glycol Lianzhong Zhang,* Dongping Shen, Zheng Zhang, and Xuejiao Wu Zhejiang Province Key Laboratory of Biofuel, College of Chemical Engineering, Zhejiang University of Technology, Hangzhou 310014, China ABSTRACT: This paper presents vapor−liquid equilibrium (VLE) measurement and correlation for water + acetonitrile + ethylene glycol. Isobaric VLE data were reported for the ternary system at p = 101.3 kPa. The NRTL model was used for the correlation with binary parameters of water + ethylene glycol being fixed as the same for water + ethanol + ethylene glycol in the literature. The correlation showed good agreement with experimental data. Mean absolute deviations were 0.15 K for equilibrium temperature and 0.0025 for vapor-phase mole fraction of acetonitrile, respectively. The reliability of the present correlation was also verified in terms of activity coefficients of water and acetonitrile and relative volatility of acetonitrile to water. With the addition of ethylene glycol, the azeotrope of water + acetonitrile can be removed at a glycol mole fraction of 0.277. Comparisons were presented for correlations available in the literature. Effect of ethylene glycol on water + acetonitrile was compared with that on water + alcohol.

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INTRODUCTION Acetonitrile is a widely used solvent in the chemical and pharmaceutical industries. Its recycle demands frequently the separation of acetonitrile and water. Because of a minimum boiling point azeotrope, separation of the aqueous mixture can not be achieved by conventional distillation. Extractive distillation can be a promising technique in which the major issue is the choice of an appropriate solvent, also called an entrainer. Modeling of the vapor−liquid equilibrium (VLE) is necessary for the evaluation of entrainer performance and for the design of an effective and economic process. Ethylene glycol is a traditional organic entrainer having favorable properties such as relatively low vapor pressure, low viscosity, and low toxicity. Because of its hydrophilic nature, it is used in extractive distillation for alcohol dehydration.1 Sometimes a salt is added for improving the solvent performance.2 For the separation of acetonitrile and water, Zhou et al.3 evaluated the entrainer performance of ethylene glycol. Results showed that the azeotrope could be removed with the addition of ethylene glycol. However, ternary VLE data have not been reported. Recent researches have been focused on the use of other organic solvents4,5 and ionic liquids,6−9 which are organic salts. To overcome the drawbacks of some ionic liquids, for example, the relatively high viscosity and relatively high price, the use of ethylene glycol with the addition of an ionic liquid has also been studied.10,11 In this case, binary parameters for water + acetonitrile, water + ethylene glycol, and acetonitrile + ethylene glycol are necessary for the modeling of VLE. Ternary VLE data for water + acetonitrile + ethylene glycol are important for testing the reliability of the model. In this work, we present VLE measurement for the ternary system. To the best of our knowledge, ternary VLE data are not available for the system in the literature. © XXXX American Chemical Society

The ternary mixtures of water + acetonitrile + ethylene glycol and water + ethanol + ethylene glycol have in common a constituent binary pair, that is, water + ethylene glycol. Model parameters for water + ethylene glycol have been obtained in the literature12 on the basis of binary VLE data for water + ethylene glycol and ternary VLE data for water + ethanol + ethylene glycol. The binary parameters have been used successfully in the modeling of water +2-propanol + ethylene glycol and water +1-propanol + ethylene glycol.12 It would be interesting to use the same binary parameters in the modeling of water + acetonitrile + ethylene glycol. Therefore, another aim of the present work is to establish reliable activity coefficient model for water + acetonitrile + ethylene glycol. The ternary VLE data, together with binary VLE data for water + acetonitrile in the literature, have been used for the optimization of binary parameters of water + acetonitrile and acetonitrile + ethylene glycol.

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EXPERIMENTAL SECTION Materials. Acetonitrile (mass fraction purity 0.998) and ethylene glycol (mass fraction purity 0.99) were supplied by Sinopharm Chemical Reagent Co. Ltd. and were used without further purification. Water was double distilled. The chemical sample descriptions are presented in Table 1. Water mass fraction was, respectively, 4.7 × 10−4 for acetonitrile and 8.3 × 10−4 for ethylene glycol. Apparatus and Procedure. An ebulliometer, which has been described in detail previously,13,14 was used for the measurement of the ternary VLE data. The experimental Received: February 15, 2017 Accepted: April 20, 2017

A

DOI: 10.1021/acs.jced.7b00178 J. Chem. Eng. Data XXXX, XXX, XXX−XXX

Journal of Chemical & Engineering Data

Article

data for water + acetonitrile by Acosta et al.5 The objective function was

Table 1. Chemical Samples Used in This Study chemical name acetonitrile ethylene glycol

source Sinopharm Chemical Reagent Co. Ltd. Sinopharm Chemical Reagent Co. Ltd.

mass fraction purity

purification method

0.998

none

0.99

none

F = Fternary + Fbinary

Fternary =

1 N

(1)

⎛ γ ∑ ⎜⎜ 1,cal γ − N ⎝ 1,exp

⎞2 ⎟ + 1 1 ⎟⎠ N

⎛ γ ∑ ⎜⎜ 2,cal γ − N ⎝ 2,exp

⎞2 ⎟ 1 ⎟⎠ (1a)

procedure was the same as that for water + ethanol + ethylene glycol.12 For the system water (1) + acetonitrile (2) + ethylene glycol (3), the measurements were performed in a way that the glycol mass fraction, w3, changed from 0.8 to 0.1, while the acetonitrile mole fraction on a glycol-free basis, x′2 = x2/(x1 + x2), remained approximately constant. In a typical run, a certain amount of acetonitrile and ethylene glycol were introduced into the ebulliometer at the beginning of measurement. Water content was determined by Karl Fischer titration. Additional water was added so that x′2 has the prescribed value. The overall synthetic mass for each component was obtained through weighing of all the samples added in or taken out of the ebulliometer. The vapor−liquid equilibrium was established in typically 45 min and the vapor condensate was analyzed. The water mass fraction was measured by Karl Fischer titration (SF3 Titrator, Zibo Zifen Instrument Ltd.). The ratio of mass fractions of acetonitrile to ethylene glycol was determined by gas chromatograph (Fuli 9790J). The gas chromatograph was equipped with a capillary column of OV-1301 (20 m × 0.32 mm × 0.25 μm) using nitrogen as carrier gas. Injector, column, and detector (FID) temperatures were, respectively, 523.2, 373.2, and 553.2 K. Vapor-phase mole fractions, y1 and y2, were thus calculated. Liquid compositions were obtained in a procedure described previous,13,15 which was based on mass balances. The next measurement started with the replacement of certain amount of mixture in the boiler with water and acetonitrile, so that w3 decreased by 0.1 and x′2 remained approximately unchanged. The measurement was repeated until w3 reached a value of 0.1. Standard uncertainties were estimated to be 0.08 K for temperature, 0.05 kPa for pressure, and 0.003 for w3. Relative standard uncertainties for y1, and y2, and x′2 were estimated to be 0.01.

Fbinary =

1 N

⎛ γ ∑ ⎜⎜ 1,cal γ − N ⎝ 1,lit

⎞2 ⎟ + 1 1 ⎟⎠ N

⎛ γ ∑ ⎜⎜ 2,cal γ − N ⎝ 2,lit

⎞2 ⎟ 1 ⎟⎠ (1b)

where N is the number of data points. For the binary pair water + acetonitrile, the energy parameters were regarded as temperature-dependent and the nonrandomness factor was treated as adjustable. It was found that these would significantly improve the correlation. For best correlation, the nonrandomness factor had a value of 0.38. On the other hand, for the binary pair acetonitrile + ethylene glycol the correlation was insensitive to the choice of the nonrandomness factor, which was therefore set as 0.3, and temperature-independent energy parameters appeared to be adequate. The results are presented in Table 3. Ternary VLE were calculated by use of the NRTL model and the optimized parameters. The results are in good agreement with the experimental values, which can be observed in Figure 1. Mean absolute deviations were, respectively, 0.0025 for acetonitrile mole fraction in the vapor phase and 0.15 K for equilibrium temperature. The reliability of the present correlation was also verified in terms of activity coefficients and relative volatility, as shown in Figures 2 and 3. Because the experimental measurements were at regular liquid-phase compositions, quality of the correlation can be observed. At the same time, the effect of ethylene glycol on the quasi-binary pair water + acetonitrile can also be observed in Figures 1 to 3. The T, x′2 and T, y′2 relations at p = 101.3 kPa are shown in Figure 1 for typical glycol mass fractions w3 = 0, 0.2, 0.4, 0.6, 0.7, and 0.8. For the binary mixture water (1) + acetonitrile (2), the correlation showed an azeotrope at T = 349.92 K and x2 = 0.683. With the addition of ethylene glycol, the boiling temperature increases. There is a minimum temperature when w3 = 0.2. Because x′2 and y′2 are not the same, it is not related to an azeotrope. The azeotrope of the quasi-binary pair is moved to x′2 = 0.811 and has nothing to do with the temperature minimum. At w3 ≥ 0.4, y′2 is always greater than x′2, indicating the breaking of azeotrope. Although the azeotrope has been removed, there is still a temperature minimum in T, x′2 and T, y′2 curves at a given glycol mass fraction. The effect of ethylene glycol can also observed in terms of the relative volatility of acetonitrile to water, as shown in Figure 2c. Under the ideal gas assumption, the relative volatility is related to the ratio of vapor pressures and the ratio of activity sat coefficients, that is, α21 = (ρsat 2 /ρ1 ) · (γ2/γ1). The vapor pressure ratio is a natural contribution to the relative volatility and is generally a weak function of temperature. For water + acetonitrile, the vapor pressure ratio decreases in some extent with the addition of glycol, as can be observed in Figure 7c for x′2 = 1. Meanwhile, the addition of glycol changes the nonideality of water and acetonitrile and affects the relative

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RESULTS AND DISCUSSION Isobaric VLE data were measured at p = 101.3 kPa and are listed in Table 2. Six data sets were measured at, respectively, x′2 = 0.1, 0.2, 0.4, 0.6, 0.8, and 0.95. Activity coefficients of water (γ1) and acetonitrile (γ2) were calculated under the ideal gas assumption and are also presented in Table 2, together with the relative volatility of acetonitrile to water (a21). In the calculation of activity coefficients, the vapor pressures were calculated by parameters available in the literature.16 Thermodynamic consistency of experimental ternary VLE data was verified by the Wisniak and Tamir17 modification of the McDermott−Ellis test.18 It was found that D < Dmax at all data points. This is an indication that the experimental data are thermodynamically consistent. The ternary VLE were modeled by the NRTL equation.19 Binary parameters for water + ethylene glycol are available in the literature and have been used for modeling water + ethanol/2-propanol/1-propanol + ethylene glycol.12 They were used and kept unchanged in this work. Binary parameters for water + acetonitrile and acetonitrile + ethylene glycol were optimized by use of the ternary data in Table 2 and binary VLE B



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Table 2. Experimental Vapor−Liquid Equilibrium Data for Temperature T, Liquid-Phase Mole Fraction on Glycol-Free Basis x′, Liquid-Phase Mass Fraction w, and Vapor-Phase Mole Fraction y, and Calculated Results for Activity Coefficient γ, and Relative Volatility α, for the Ternary System Water (1) + Acetonitrile (2) + Ethylene Glycol (3) at p = 101.3 kPaa

a

x′2

w3

T/K

y1

0.100 0.101 0.101 0.101 0.101 0.0996 0.101 0.0992

0.798 0.701 0.600 0.500 0.401 0.300 0.200 0.101

384.65 375.03 368.80 364.52 361.47 359.18 357.27 355.90

0.579 0.547 0.520 0.506 0.490 0.483 0.470 0.466

0.200 0.200 0.200 0.201 0.199 0.201 0.201 0.201

0.799 0.699 0.600 0.501 0.399 0.301 0.199 0.101

379.61 369.26 363.34 359.54 357.17 355.24 353.56 352.57

0.411 0.393 0.384 0.379 0.387 0.387 0.383 0.389

0.399 0.399 0.401 0.399 0.401 0.401 0.400 0.400

0.799 0.700 0.602 0.500 0.400 0.299 0.200 0.100

374.47 365.50 360.58 357.33 355.11 353.50 352.29 351.31

0.237 0.239 0.256 0.282 0.293 0.317 0.329 0.345

0.601 0.601 0.600 0.599 0.599 0.600 0.600 0.599

0.800 0.701 0.599 0.499 0.399 0.299 0.200 0.100

373.00 364.93 360.47 357.67 355.61 353.93 352.47 351.14

0.144 0.160 0.178 0.200 0.225 0.248 0.276 0.304

0.800 0.800 0.799 0.800 0.800 0.799 0.801 0.799

0.799 0.699 0.599 0.500 0.399 0.301 0.200 0.099

372.54 365.28 361.58 359.09 357.10 355.35 353.62 351.76

0.0628 0.0799 0.0959 0.115 0.139 0.166 0.193 0.229

0.950 0.950 0.950 0.950 0.950 0.950 0.951 0.951

0.801 0.700 0.601 0.500 0.400 0.302 0.201 0.100

373.13 366.48 363.21 361.03 359.43 357.93 356.41 354.78

0.0154 0.0192 0.0246 0.0320 0.0405 0.0522 0.0687 0.0864

y2 x′2 = 0.1 0.405 0.445 0.476 0.491 0.508 0.516 0.529 0.534 x′2 = 0.2 0.573 0.599 0.611 0.619 0.612 0.613 0.617 0.610 x′2 = 0.4 0.748 0.754 0.740 0.716 0.706 0.682 0.670 0.655 x′2 = 0.6 0.842 0.832 0.817 0.797 0.773 0.750 0.723 0.696 x′2 = 0.8 0.921 0.910 0.898 0.880 0.856 0.831 0.805 0.771 x′2 = 0.95 0.969 0.969 0.967 0.961 0.953 0.943 0.927 0.911

γ1

γ2

γ3

α21

0.99 1.00 1.01 1.02 1.02 1.03 1.03 1.03

3.98 4.32 4.65 4.81 5.01 5.16 5.27 5.38

0.76 0.80 0.76 0.84 0.66 0.85 0.73 0.69

6.29 7.27 8.20 8.64 9.23 9.67 10.08 10.39

1.00 1.04 1.06 1.08 1.09 1.10 1.10 1.11

3.42 3.60 3.65 3.63 3.55 3.47 3.47 3.39

0.93 1.11 1.02 0.78 0.67 0.83 0.66 0.94

5.57 6.11 6.37 6.47 6.38 6.30 6.40 6.24

1.03 1.06 1.13 1.22 1.25 1.32 1.35 1.39

2.89 2.76 2.57 2.38 2.25 2.10 2.01 1.91

1.05 0.95 0.99 0.86 0.96 0.81 0.76 0.86

4.75 4.74 4.33 3.82 3.60 3.22 3.05 2.84

1.11 1.20 1.26 1.35 1.46 1.57 1.71 1.86

2.50 2.24 2.02 1.84 1.68 1.56 1.46 1.38

1.00 1.03 0.95 0.96 1.16 1.13 1.20 1.72

3.88 3.44 3.06 2.66 2.30 2.02 1.74 1.53

1.07 1.26 1.37 1.53 1.77 2.03 2.33 2.74

2.27 1.96 1.71 1.53 1.38 1.28 1.19 1.13

1.10 1.27 1.22 1.47 1.71 1.79 2.16 2.45

3.66 2.84 2.35 1.93 1.54 1.25 1.04 0.85

1.10 1.22 1.39 1.63 1.93 2.36 3.04 3.76

2.13 1.79 1.55 1.37 1.24 1.15 1.08 1.03

1.02 1.31 1.31 1.60 1.97 2.29 3.52 4.14

3.31 2.66 2.07 1.59 1.24 0.95 0.70 0.55

u(T) = 0.08 K, u(p) = 0.05 kPa, ur(x′2) = 0.01, u(w3) = 0.003, ur(y1) = 0.01, ur(y2) = 0.01.

of glycol. This can be related to the increase of γ2 (Figure 2b) and rapid decrease of γ1 (Figure 2a). In the water-rich region,

volatility more significantly. In the acetonitrile-rich region, for example, at x′2 = 0.95 or x′2 = 1, α21 increases with the addition C



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Table 3. Estimated Values of Binary Parameters in the NRTL Equationa

a

component i

component j

aij

bij/K

aji

bji/K

cij

water water acetonitrile

acetonitrile ethylene glycol ethylene glycol

0.5508 0 0

423.59 335.18 551.76

3.4214 0 0

−916.58 −303.17 95.310

0.38 0.3 0.3

τij = Δgij/RT = aij + bij/T; Gij = exp(−cijτij). The binary parameters of water + ethylene glycol were taken from ref 12.

azeotrope of water + acetonitrile can be broken with the addition of dimethyl sulfoxide at a mole fraction of 0.4. In the case of butyl acetate, according to VLE results by Acosta et al.,5 the solvent can only move the azeotrope to the pure acetonitrile side at solvent mole fractions up to 0.5. NRTL parameters for VLE of water + acetonitrile + ethylene glycol are available in the database of Aspen Plus, that is, APV80 VLE-IG, and have been presented by Liu et al.11 The latter, as it is reported, were taken from the database of ChemCAD. Activity coefficients of water and acetonitrile and relative volatility of acetonitrile to water were calculated using these model parameters. Typical results at x′2 = 0.1 and x′2 = 0.95 are shown in Figure 4 in comparison with the experimental data and correlation in this work. Results at x′2 = 1 are shown in Figure 5. Generally good agreement can be observed for the results of APV80 VLE-IG. For breaking the azeotrope of water + acetonitrile, the calculated minimum mole fraction is 0.281, which is very close to the value of 0.277 in the present correlation (Figure 5c). However, as has been presented previous,12 APV80 VLE-IG showed large departure for activity coefficient of water for water + ethylene glycol in the glycol-rich end. For the correlation of Liu et al.,11 the calculated infinite dilution activity coefficient of water in acetonitrile is 9.17 (Figure 5a). This is significantly larger than the present correlation (5.68) and APV80 VLE-IG (5.31). With the addition of glycol, the activity coefficient of water decreases more rapidly in the correlation of Liu et al.11 As a consequence, the calculated minimum mole fraction for breaking the azeotrope is 0.249, which is apparently smaller than the present correlation (0.277) and APV80 VLE-IG (0.281). For further comparison of the correlations, isobaric VLE data were calculated for the binary system water + acetonitrile. Results at p = 101.3 kPa are shown in Figure 6, in comparison with literature data of Acosta et al.,5 Liu et al.,11 Maslan and Stoddard,20 and Blackford and York.21 Data of Acosta et al.5

Figure 1. T−x−y diagram for water (1) + acetonitrile (2) + ethylene glycol (3) at p = 101.3 kPa: ○, ●, w3 = 0.2; □, ■, w3 = 0.4; ◇, ◆, w3 = 0.6; ▶, ◀, w3 = 0.7; ▲, ▼, w3 = 0.8; Lines were calculated by NRTL with parameters in Table 3: solid lines, w3 = 0.2, 0.4, 0.6, 0.7, and 0.8, respectively; dash line, w3 = 0.

for example, at x′2 = 0.1, α21 decreases with the addition of glycol. This is mainly due to the rapid decrease of γ2 (Figure 2b) and the decrease of the vapor pressure ratio. In Figure 3c, the trend of the relative volatility can be observed with varying x′2 at various fixed w3. With the increase of x′2, α21 decreases rapidly at all given w3. This is resulted from both the decrease of γ2 (Figure 3b) and increase of γ1 (Figure 3a). The minimum amount of ethylene glycol for breaking the water + acetonitrile azeotrope can be determined according to the trend of α21, in relation with x3, at x′2 = 1. Breaking the azeotrope requires that α21 > 1. As shown in Figure 2c, the azeotrope is removed at a glycol mole fraction of 0.277 (mass fraction 0.367). In comparison with literature results of other organic solvents, the performance of ethylene glycol appeared to be more favorable. As reported by Zhang et al.,4 the

Figure 2. Experimental and calculated (a) activity coefficients of water, γ1, (b) activity coefficients of acetonitrile, γ2, and (c) relative volatility of acetonitrile to water, α21, in relation with glycol mole fraction, x3, for water (1) + acetonitrile (2) + ethylene glycol (3) at p = 101.3 kPa: ○, x′2 = 0.1; ●, x′2 = 0.2; □, x′2 = 0.4; ■, x′2 = 0.6; ◇, x′2 = 0.8; ◆, x′2 = 0.95. Lines were calculated by NRTL with parameters in Table 3: solid lines, x′2 = 0.1, 0.2, 0.4, 0.6, 0.8, and 0.95, respectively; dash line, x′2 = 1. D



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Figure 3. Experimental and calculated (a) activity coefficients of water, γ1, (b) activity coefficients of acetonitrile, γ2, and (c) relative volatility of acetonitrile to water, α21, in relation with acetonitrile mole fraction on glycol-free basis, x′2, for water (1) + acetonitrile (2) + ethylene glycol (3) at p = 101.3 kPa: ○, w3 = 0.1; ●, w3 = 0.2; □, w3 = 0.3; ■, = 0.4; ◇, w3 = 0.5; ◆, w3 = 0.6; Δ, w3 = 0.7;▲, w3 = 0.8; Lines were calculated by NRTL with parameters in Table 3: solid lines, w3 = 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, and 0.8, respectively; dash line, w3 = 0.

Figure 4. Experimental and calculated (a) activity coefficients of water, γ1, (b) activity coefficients of acetonitrile, γ2, and (c) relative volatility of acetonitrile to water, α21, in relation with glycol mole fraction, x3, for water (1) + acetonitrile (2) + ethylene glycol (3) at p = 101.3 kPa: ○, x2′ = 0.1; □, x2′ = 0.95; Lines were calculated by model parameters: solid line, this work in Table 3; dash line, Liu et al. (ref 11); dot line, APV80 VLE-IG.

Figure 5. Calculated results of (a) activity coefficients of water, γ1, (b) activity coefficients of acetonitrile, γ2, and (c) relative volatility of acetonitrile to water, α21, in relation with glycol mole fraction, x3, for water (1) + acetonitrile (2) + ethylene glycol (3) at x′2 = 1 and p = 101.3 kPa: solid line, this work in Table 3; dash line, Liu et al. (ref 11); dot line, APV80 VLE-IG (results of γ2 coincide with Liu et al.).

for the data of Maslan and Stoddard,20 except individual data points, and for the correlation of APV80 VLE-IG. There are relatively large deviations for the data of Liu et al.11 and Blackford and York,21 and for the correlation of Liu et al.11 It is noticeable that the correlation of Liu et al.11 showed good agreement with the data of Blackford and York.21 Effect of ethylene glycol (3) on water (1) + acetonitrile (2) was compared with those on water (1) + ethanol (2), water (1)

have been used in the present correlation. The present correlation provides good agreement with the data of Acosta et al.5 Mean absolute deviations were 0.19 K for equilibrium temperature and 0.0070 for vapor-phase mole fraction, respectively. The deviations are smaller than those using the parameters in the original literature. The later has respectively deviations of 0.28 K for temperature and 0.0083 for vaporphase mole fraction. Generally close agreement can be observed E



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coefficients and on the vapor pressure ratio. As compared with the alcohols, aqueous mixture of acetonitrile shows more significant decrease in γ1 (Figure 7a) and increase in γ2 (Figure 7b), with the addition of glycol. As a consequence, the relative volatility α21 increases more rapidly (Figure 7d). It should be noted that there is an apparent decrease in the vapor pressure ratio for water + acetonitrile (Figure 7c). This is unfavorable for the increase of relative volatility. On the other hand, infinite dilution activity coefficient of water has the highest value in acetonitrile (Figure 7a). This accounts for the low relative volatility, which is comparable with 1-propanol, at x3 = 0. As a result, removing the azeotrope requires more ethylene glycol (x3 = 0.277) than 2-propanol (x3 = 0.240) and ethanol (x3 = 0.072) and less than 1-propanol (x3 = 0.550).

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CONCLUSIONS Isobaric VLE data for water + acetonitrile + ethylene glycol were measured at 101.3 kPa. The phase equilibrium behavior was modeled using the NRTL equation. The correlation is in good agreement with the experimental data, with mean absolute deviations of, respectively, 0.0025 for acetonitrile mole fraction in the vapor phase and 0.15 K for equilibrium temperature. The reliability of the present correlation was also verified in terms of activity coefficients and relative volatility. Results showed that the minimum mole fraction of ethylene glycol for breaking the azeotrope of water + acetonitrile was 0.277. Comparisons were presented for correlations available in the literature. Effect of ethylene glycol on water + acetonitrile was compared with those on water + ethanol, water + 2propanol and water + 1-propanol.

Figure 6. Composition diagram for the vapor−liquid equilibrium of water (1) + acetonitrile (2) at p = 101.3 kPa: ○, Acosta et al. (ref 5); □, Liu et al. (ref 11); Δ, Maslan and Stoddard (ref 20); ◇, Blackford and York (ref 21). Lines were calculated by model parameters: solid line, this work in Table 3; dash line, Liu et al. (ref 11); dot line, APV80 VLE-IG.

+ 2-propanol (2), and water (1) + 1-propanol (2).12 Activity coefficients, vapor pressure ratio, and relative volatility were calculated for saturated ternary mixtures at x′2 = 1 and p = 101.3 kPa and are shown in Figure 7 in relation with x3. The effect on relative volatility can be related to the effect on activity

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AUTHOR INFORMATION

Corresponding Author

*Tel.: +86 571 88320892. E-mail: [email protected]. ORCID

Lianzhong Zhang: 0000-0001-6596-8248 Funding

The authors wish to acknowledge the financial support by the National Natural Science Foundation of China (21476205). Notes

The authors declare no competing financial interest.

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REFERENCES

(1) Washall, T. A. Separation of water from a single alkanol by extractive distillation with ethylene glycol. U.S. Patent 3,464,896, 1969. (2) Lei, Z.; Wang, H.; Zhou, R. Influence of salt added to solvent on extractive distillation. Chem. Eng. J. 2002, 87, 149−156. (3) Zhou, J. B.; Cui, X. B.; Dong, B. L.; Wang, Y. F.; Chen, Z. K. Separation of acetonitrile and water mixture by batch extractive distillation. Chem. Ind. Eng. 2009, 26, 482−486. (4) Zhang, Z.; Lv, M.; Huang, D.; Jia, P.; Sun, D.; Li, W. Isobaric vapor−liquid equilibrium for the extractive distillation of acetonitrile + water mixtures using dimethyl sulfoxide at 101.3 kPa. J. Chem. Eng. Data 2013, 58, 3364−3369. (5) Acosta, J.; Arce, A.; Rodil, E.; Soto, A. A thermodynamic study on binary and ternary mixtures of acetonitrile, water and butyl acetate. Fluid Phase Equilib. 2002, 203, 83−98. (6) Pereiro, A. B.; Araújo, J. M. M.; Esperança, J. M. S. S.; Marrucho, I. M.; Rebelo, L. P. N. Ionic liquids in separations of azeotropic systems − A review. J. Chem. Thermodyn. 2012, 46, 2−28. (7) Li, T.; Yang, Q.; Ding, H.; Li, J.; Peng, C.; Liu, H. Amino acid based ionic liquids as additives for the separation of an acetonitrile and water azeotropic mixture: COSMO-RS prediction and experimental verification. Ind. Eng. Chem. Res. 2015, 54, 12143−12149.

Figure 7. Calculated results of (a) activity coefficient of water, γ1, (b) activity coefficient of an alcohol or acetonitrile, γ2, and (c) vapor sat pressure ratio of an alcohol or acetonitrile to water, psat 2 /p1 , (d) relative volatility of an alcohol or acetonitrile to water, α21, in relation with glycol mole fraction, x3, for saturated mixtures water (1) + acetonitrile/ethanol/2-propanol/1-propanol (2) + ethylene glycol (3) at x′2 = 1 and p = 101.3 kPa: solid line, acetonitrile in this work; dash line, ethanol (ref 12); dot line, 2-propanol (ref 12); dash-dot line, 1propanol (ref 12). F



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