Isobaric Vapor–Liquid Equilibrium for Ethyl Acetate + Acetonitrile + 1

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Isobaric Vapor−Liquid Equilibrium for Ethyl Acetate + Acetonitrile + 1‑Butyl-3-methylimidazolium Hexafluorophosphate at 101.3 kPa Qunsheng Li,† Ling Cao,† Xueting Sun,† Panpan Liu,† and Baohua Wang*,‡ †

State Key Laboratory of Chemical Resource Engineering, Beijing University of Chemical Technology, Box 35, Beijing, 100029 China College of Chinese Pharmacology, Beijing University of Chinese Medicine and Pharmacology, Beijing, 100029 China

‡

ABSTRACT: Vapor−liquid equilibria for the binary system ethyl acetate + acetonitrile and for the ternary system ethyl acetate + acetonitrile + 1-butyl-3-methylimidazolium hexafluorophosphate ([BMIM]+[PF6]−) at 101.3 kPa have been obtained with a modified Othmer still. The experimental vapor−liquid equilibrium data were correlated using the NRTL model proposed by Renon and Prausnitz, and the parameters were obtained. The results showed that [BMIM]+[PF6]− produced a consistent salting-out effect of ethyl acetate over the whole range of the liquid concentrations, which increased the relative volatility of ethyl acetate to acetonitrile and even eliminated the azeotropic phenomenon when the mole fraction of [BMIM]+[PF6]− was up to 0.05.

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INTRODUCTION Ionic liquids (ILs) are promising entrainers with a specific attractive blend of physical properties if their chemical structures are tailored properly. They can meet the requirement for suitable entrainers that should possess both high solvent capacity and high selectivity for the components to be separated.1 Since Arlt and co-workers discussed the potential of ILs for the field of extractive distillation for the separation of azeotropic and close-boiling systems for the first time,2 increasing concern on azeotrope breaking using ILs has been given. A large number of publications available show the upsurge of interest in using ILs as entrainers for separating the azeotropic systems. A critical review about ILs used in extractive distillation has been given in the literature.3 ILs gain an advantage over conventional organic liquid salts and inorganic solid salts as entrainers for separating azeotropic systems, mainly due to the following reasons: no effective vapor pressure, thermal stability, wide liquid range, good solvents for a lot of organic and inorganic substances, and less corrosivity than inorganic solid salts. ILs represent a promising class of entrainers for separating processes.4−6 Acetonitrile is a core solvent in the chemical industries. Several key properties have made acetonitrile very popular. High dielectric constant, excellent solvation ability, favorable optical performance, low proton availability, low freezing/ boiling points, low viscosity, and relatively low toxicity all contribute to its favorable properties.7−9 However, acetonitrile is usually difficult to purify using conventional distillation processes, particularly with respect to compounds such as ethyl acetate and acetonitrile which can form an azeotrope. But this mixture is common in analyzing pharmaceutical wastewater because ethyl acetate and acetonitrile are excellent organic solvents.10 According to already published papers, Smith B.D. © 2013 American Chemical Society

has reported the VLE data of ethyl acetate and acetonitrile at (313.15, 353.15, and 393.15) K,11 and Jiandong Di showed that n-hexane could successfully serve as the entrainer of batch azeotropic distillation for such mixture separation,12 but we found no literature using ILs for separating them. In this work, isobaric vapor−liquid equilibrium (VLE) data for ethyl acetate and the acetonitrile binary system and ternary system containing 1-butyl-3-methylimidazolium hexafluorophosphate ([BMIM]+[PF6]−) were both presented at 101.3 kPa, and the effect of [BMIM]+[PF6]− on the VLE of ethyl acetate and acetonitrile system was also discussed.

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EXPERIMENTAL SECTION Chemicals. The chemical reagents used were ethyl acetate, acetonitrile, and [BMIM]+[PF6]−. Ethyl acetate was obtained from Tianjin JinKe Fine Chemical Industry Research Institute, China, and the purity was not less than 99.5 % (weight ratio). Acetonitrile was purchased from Tianjin Fuchen Chemical Reagents Factory, China, and the purity was not less than 99.8 % (weight ratio). Ethyl acetate and acetonitrile were checked by gas chromatography and used without further purification. The water mass fractions in the ethyl acetate and acetonitrile determined by Karl Fisher titration were 0.025 % and 0.023 %, respectively. The [BMIM]+[PF6]− was purchased from Shanghai Cheng Jie Chemical Co. LTD, China, with the purity more than 98.0 % (weight ratio) checked by liquid chromatography. The water mass fraction in the IL determined by Karl Fisher titration was xW < 0.054 %. Prior treatment of [BMIM]+[PF6]− and its recovery were both carried by rotary Received: September 30, 2012 Accepted: April 1, 2013 Published: April 8, 2013 1112

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Table 1. Specifications of Chemical Samples chemical name ethyl acetate acetonitrile [BMIM]+[PF6]−a

source

mass fraction purity

Tianjin JinKe Fine Chemical Industry Research Institute Tianjin Fuchen Chemical Reagents Factory Shanghai Cheng Jie Chemical Co.

purification method

final water mass fraction

analysis method

0.995

none

0.00025

GCb, KFd

0.998 0.980

none rotary evaporation under a vacuum

0.00023 0.00054

GCb, KFd LCc, KFd

a [BMIM]+[PF6]− = 1-butyl-3-methylimidazolium hexafluorophosphate. bGC = gas chromatography. cLC = liquid chromatography. dKF = Karl Fischer titration.

evaporation for 48 h at 393 K under a vacuum. The specifications of used chemicals were summarized in Table 1. Apparatus and Procedure. A modified Othmer still was used to measure VLE data at local atmospheric pressure. The details about this apparatus were described in our previous publication.13 The amounts of ethyl acetate and acetonitrile contained in the liquid and condensed vapor phases were analyzed by gas chromatography (SP7800, China) with a thermal conductivity detector. The chromatographic column (3 m × 3 mm) was packed with Porapak-Q. The carrier gas was hydrogen, and its flow was 45 cm3·min−1. And the operating conditions were as follows: the injector temperature at 423 K, the oven temperature at 413 K, and the detector temperature at 443 K. The equilibrium temperature was measured by a mercury thermometer with an uncertainty of 0.1 K. Since the equilibrium pressure was kept at local atmospheric pressure, the equilibrium temperature was corrected to 101.3 kPa using the method indicated by the literature.14 The local atmospheric pressure was measured by a barometer with an uncertainty of 0.1 kPa. To eliminate the influence of ILs on the gas chromatography, we used a trap located between the injector and the chromatographic column to retain ILs. In this way, the result of the analysis was not affected by the presence of the ILs, as we were able to experimentally verify. The trap was periodically cleaned to prevent the ILs from coming into the column. A calibration curve was obtained from a set of gravimetrically prepared standard solutions by an electronic balance with an uncertainty of 0.1 mg, which allowed us to quantify the amounts of ethyl acetate and acetonitrile in the samples. In this way, the maximum uncertainty of mole fraction of ethyl acetate and acetonitrile was 0.002. The mole fraction of IL in the liquid phase was determined by measuring the mass difference of liquid phase with and without IL.

Table 2. Vapor−Liquid Equilibrium Data for Real Atmospheric Pressure H0, Experimental Temperature Ta, Experimental Temperatures Corrected to 101.3 kPa T, Liquid-Phase Mole Fraction x, and Gas-Phase Mole Fraction y, for the Ethyl Acetate (1) + Acetonitrile (2) System at 0.1 MPaa H0/kPa

Ta/K

T/K

x1

y1

100.6 100.6 100.6 100.6 100.6 100.6 100.6 100.8 100.8 100.8 101.1 100.8

353.8 352.7 351.1 349.9 349.1 348.5 348.2 348.2 348.3 348.7 349.4 349.6

354.3 353.2 351.6 350.4 349.6 349.0 348.7 348.5 348.6 349.0 349.5 349.9

0.000 0.048 0.145 0.243 0.345 0.447 0.550 0.648 0.745 0.852 0.947 1.000

0.000 0.080 0.215 0.316 0.408 0.492 0.577 0.653 0.736 0.830 0.938 1.000

a

Standard uncertainties u are u(H0) = 0.1 kPa, u(Ta) = 0.1 K, and the combined standard uncertainty uc are uc(T) = 0.2 K, uc(x1) = uc(y1) = 0.002.

Table 3. Mean Absobute Deviations, δy and δT, between Experimental and Calculated Values of the Vapor-Phase Mole Fraction and the Equilibrium Temperature at 101.3 kPa system

δya

δTb/K

ethyl acetate + acetonitrile ethyl acetate + acetonitrile + [BMIM]+[PF6]−

0.008 0.003

0.2 0.3

δy = (1/N)∑|yexptl − ycalcd| bδT = (1/N)∑|Texptl − Tcalcd|. N is the number of experimental points.

a

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RESULTS AND DISCUSSION Ethyl Acetate + Acetonitrile System. The binary VLE for the system of ethyl acetate (1) + acetonitrile (2) was obtained at 101.3 kPa. The data for the binary system of ethyl acetate (1) + acetonitrile (2) were listed in Table 2. In this table, H0 is the real atmospheric pressure, Ta is the experimental temperature at the real atmospheric pressure, T is the experimental temperatures corrected to 101.3 kPa, and x1 and y1 are the mole fractions of ethyl acetate. The experimental data show a minimum boiling point azeotrope at x1 = 0.682 and T = 348.5 K when the pressure is 101.3 kPa, which can be interpolated from the experimental values. The mean absolute deviations between calculated, using the NRTL model, and measured mole fractions of ethyl acetate in the vapor phase δy and equilibrium temperature δT were reported in Table 3, showing that the values are thermodynamically consistent. Ethyl Acetate + Acetonitrile + [BMIM]+[PF6]− System. VLE data for ethyl acetate (1) + acetonitrile (2) +

[BMIM]+[PF6]− (3) system at 101.3 kPa, were obtained by trying to keep the IL mole fraction constant in each of the four series at x3 ≈ 0.05, 0.10, 0.15, and 0.20. Complete H0, Ta, T, x1 and y1 data were obtained. These values are shown in Table 4, where x3 is the mole fraction of [BMIM]+[PF6]− in the liquid phase; x1 is the mole fractions of ethyl acetate in the liquid phase expressed on an IL-free basis, y1 is the mole fractions of ethyl acetate in the vapor phase; and T is the equilibrium temperature corrected to 101.3 kPa. Modeling the Phase Equilibrium. The NRTL model proposed by Renon and Prausnitz15 has been commonly used for the correlation of experimental VLE data involving ILs in several studies,16−22 and it gives good agreement with the experimental results. Our experimental VLE data for ethyl acetate (1) + acetonitrile (2) + [BMIM]+[PF6]− (3) were also correlated by the NRTL model of Renon and Prausnitz. To represent the VLE data involving IL, it is necessary to 1113

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Table 4. Vapor−Liquid Equilibrium Data for Liquid-Phase Mole Fraction of [BMIM]+[PF6]− x3, Real Atmospheric Pressure H0, Experimental Temperature Ta, Experimental Temperatures Corrected to 101.3 kPa T, Liquid-Phase Mole Fraction Expressed on an IL-Free Basis x, and Gas-Phase Mole Fraction y, for the Ethyl Acetate (1) + Acetonitrile (2) + [BMIM]+[PF6]− (3) System at 0.1 MPaa 100x3

H0/kPa

Ta/K

T/K

x1

y1

100x3

H0/kPa

Ta/K

T/K

x1

y1

4.999 5.001 5.007 5.003 5.008 5.001 5.004 5.005 4.977 5.001 5.007 4.997 10.005 9.998 10.002 9.999 10.004 10.001 10.004 10.004 10.000 10.000 10.006 10.020

100.8 101.1 100.6 100.6 100.6 100.6 100.6 100.6 100.6 100.6 100.6 100.8 100.8 101.2 100.6 100.6 100.6 100.6 100.7 100.6 100.7 101.2 101.1 100.7

356.4 354.3 352.1 350.9 350.0 349.4 349.1 348.5 348.7 348.7 348.9 349.2 359.6 356.7 354.2 352.6 351.5 350.7 350.2 349.9 349.8 350.0 350.1 349.8

356.8 354.4 352.6 351.4 350.5 349.9 349.6 349.0 349.2 349.2 349.4 349.5 360.0 356.8 354.7 353.1 352.0 351.2 350.6 350.4 350.2 350.1 350.2 350.2

0.000 0.100 0.196 0.295 0.391 0.494 0.597 0.697 0.797 0.898 0.948 1.000 0.000 0.098 0.196 0.298 0.393 0.493 0.597 0.699 0.798 0.898 0.950 1.000

0.000 0.176 0.307 0.415 0.505 0.586 0.663 0.744 0.822 0.906 0.950 1.000 0.000 0.188 0.330 0.439 0.538 0.620 0.697 0.773 0.844 0.921 0.960 1.000

15.000 15.006 14.989 14.992 14.996 15.002 15.004 14.631 14.999 14.993 14.996 15.008 20.006 20.004 19.995 20.007 19.992 19.994 19.998 20.008 19.947 19.999 19.998 19.997

100.7 100.7 100.7 100.7 100.7 100.8 100.8 100.8 100.8 100.7 100.7 100.8 100.8 101.1 100.8 100.6 100.7 100.7 100.7 100.7 100.6 100.6 100.6 100.7

362.3 358.8 356.4 354.4 353.2 351.9 351.2 350.5 350.3 350.0 349.8 349.7 366.4 361.8 359.1 356.8 355.0 353.6 352.5 351.8 351.1 350.7 350.4 350.6

362.8 359.3 356.8 354.8 353.6 352.3 351.6 350.9 350.6 350.4 350.2 350.0 366.8 362.0 359.5 357.3 355.4 354.0 352.9 352.2 351.6 351.2 350.9 351.0

0.000 0.098 0.190 0.286 0.385 0.488 0.593 0.687 0.792 0.891 0.943 1.000 0.000 0.104 0.184 0.280 0.375 0.483 0.594 0.681 0.778 0.883 0.948 1.000

0.000 0.199 0.345 0.459 0.555 0.640 0.719 0.787 0.860 0.925 0.959 1.000 0.000 0.229 0.360 0.478 0.581 0.663 0.738 0.802 0.862 0.930 0.968 1.000

a

Standard uncertainties u are u(Ta) = 0.1 K, u(H0) = 0.1 kPa, and the combined standard uncertainty uc are uc(T) = 0.2 K, uc(x1) = uc(y1) = 0.002, uc(x3) = 0.001.

Table 5. Estimated Values of Binary Parameters Δgij and Δgji in the NRTL Model i component

j component

αij

Δgij/J·mol−1

Δgji/J·mol−1

ethyl acetate (1) ethyl acetate (1) acetonitrile (2)

acetonitrile (2) [BMIM]+[PF6]−(3) [BMIM]+[PF6]−(3)

0.30 0.11 0.45

2669.7 28107.0 9026.0

−1268.2 −13401.0 −6709.0

IL, and acetonitrile-IL were obtained from the ternary VLE data shown in Table 4 by minimizing the objective function F:

determine the binary adjustable parameters for each of the ethyl acetate−acetonitrile, ethyl acetate−IL, and acetonitrile−IL pairs in the system. In our system, nine binary adjustable parameters for three pairs must be determined. Of them, six are energy parameters and three are nonrandomness factors. To get these parameters, the assumption of an ideal behavior is adopted for the vapor, and the equilibrium conditions are expressed by the following equation: yP = xi′γiPis i

F=

∑ [(1 − γ1calcd/γ1exptl)2 + (1 − γ2calcd/γ2exptl)2 ] n

(2)

where the indices exptl and calcd denote the experimental and calculated values, respectively; and the summation is extended to the whole range of data points. With the NRTL model and the parameters shown in Table 5, we can compute the composition in the vapor phase for each composition and the equilibrium temperature. Thus, the mean absolute deviations between calculated and measured mole fractions of ethyl acetate in the vapor phase δy and equilibrium temperature δT were also reported in Table 3 for this ternary system. In Figures 1 and 2, we can see that the NRTL model of Renon and Prausnitz can well reproduce the experimental VLE data. In Figure 1, points of calculated and experimental VLE of the ethyl acetate (1) + acetonitrile (2) + [BMIM]+[PF6]− (3) system are given on (y1, x1) diagram for x3 ≈ 0, 0.05, 0.10, 0.15, and 0.20. In Figure 2, (T, x1, y1) diagram is presented for x3 ≈ 0, 0.10, 0.15 and 0.20, the experimental and calculated values for x3 ≈ 0.05 being omitted for clarity.

(1)

in which yi represents the vapor-phase mole fraction of component i; P is the total pressure of the whole system, equaling to 101.3 kPa; x′i represents the liquid-phase mole fraction of component i including IL; γi is the activity coefficient of component i obtained from the NRTL model; and Psi is the vapor pressure of pure component i at equilibrium temperature and is calculated by the Antoine equation. The Antoine constants of ethyl acetate and acetonitrile came from the literature.23 The parameters of the NRTL model for ethyl acetate (1) + acetonitrile (2) were first obtained from the VLE data of the ethyl acetate (1) + acetonitrile (2) system shown in Table 2, and then, those parameters corresponding to the ethyl acetate1114

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acetate and [BMIM]+[PF6]− is weaker than the interaction between acetonitrile and [BMIM]+[PF6]−. Consequently, the attractive interaction between IL and ethyl acetate is smaller than that between IL and acetonitrile, which leads to a decreased activity of acetonitrile and increased relative volatility of ethyl acetate to acetonitrile, as shown in Figures 3 and 4.

Figure 1. Isobaric VLE diagram for ethyl acetate (1) + acetonitrile (2) + [BMIM]+[PF6]− (3) system at 101.3 kPa: ●, x3 = 0; ■, x3 = 0.05; ▲, x3 = 0.10; ▼, x3 = 0.15; ★, x3 = 0.20; solid lines, correlated using the NRTL model.

Figure 3. Experimental and calculated activity coefficients of ethyl acetate, γ1, and acetonitrile, γ2, in relation with ethyl acetate mole fraction on an IL-free basis for the mixture ethyl acetate (1) + acetonitrile (2) + [BMIM]+[PF6]− (3) at 101.3 kPa: ●, γ1 (x3 = 0); ○, γ2 (x3 = 0); ■, γ1 (x3 = 0.05); □, γ2 (x3 = 0.05); ▲, γ1 (x3 = 0.10); △, γ2 (x3 = 0.10); ▼, γ1 (x3 = 0.15); ▽, γ2 (x3 = 0.15); ★, γ1 (x3 = 0.20); ☆, γ2 (x3 = 0.20); solid lines, correlated using the NRTL model.

Figure 2. T, x, y diagram for the ternary system of ethyl acetate (1) + acetonitrile (2) containing [BMIM]+[PF6]− (3) at different contents of IL at 101.3 kPa: ●, x1 (x3 = 0); ○, y1 (x3 = 0);▲, x1 (x3 = 0.10); △, y1 (x3 = 0.10); ▼, x1 (x3 = 0.15); ▽, y1 (x3 = 0.15); ★, x1 (x3 = 0.20); ☆, y1 (x3 = 0.20); solid lines, correlated using the NRTL model. Figure 4. Relative volatility of ethyl acetate (1) to acetonitrile (2) at 101.3 kPa: ●, x3 = 0; ■, x3 = 0.05; ▲, x3 = 0.10; ▼, x3 = 0.15; ★, x3 = 0.20; solid lines, correlated using the NRTL model.

In Figure 1, the addition of [BMIM]+[PF6]− to the binary azeotropic mixture leads to a noticeable increased mole fraction of ethyl acetate in the vapor phase. Ethyl acetate was salted out from the mixed solvent over the whole range of the liquid concentrations, the effect being more noticeable as the amount of IL increases. This consistent salting-out effect is appreciable and rare, because the crossover effect, in which both salting-out effect and salting-in emerge at a different range of the whole liquid concentrations, has been frequently pointed out in the systems with ILs by many papers.24−29 In a solution of highly dielectric solvent, ILs can be treated as weak electrolytes. Because of the higher polarity of acetonitrile compared with the polarity of ethyl acetate, the selective interaction between ethyl

It is worth noting that a small concentration of ILs produced a displacement of the azeotropic point of the ethyl acetate + acetonitrile system toward x1 value higher than 0.682 until the azeotrope disappeared, as seen in Figure 2. When the mole fraction of [BMIM]+[PF6]− reached 0.05, the azeotropy could be totally broken. The addition of IL also caused the elevation of boiling point at atmospheric pressure, as shown in Figure 3. The equilibrium temperature became higher with an increasing amount of ILs in the mixture of ethyl acetate and acetonitrile. 1115

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(13) Li, Q.; Xing, Fengying; Lei, Z.; Wang, Baohua; Chang, Q. Isobaric Vapor−Liquid Equilibrium for Isopropanol + Water + 1Ethyl-3-methylimidazolium Tetrafluoroborate. J. Chem. Eng. Data 2008, 53, 275−279. (14) Hiaki, T.; Kawai, A. Vapor−Liquid Equilibria Determination for Ahydrofluoroether with Several Alcohols. Fluid Phase Equilib. 1999, 158−160, 979−989. (15) Renon, H.; Prausnitz, J. M. Local Compositions in Thermodynamic Excess Functions for Liquid Mixtures. AIChE J. 1968, 14, 135−144. (16) Li, Q.; Zhang, J.; Lei, Z.; Zhu, J.; Wang, B.; Huang, X. Isobaric Vapor−Liquid Equilibrium for (Propan-2-ol + Water + 1-Butyl-3methylimidazolium Tetrafluoroborate. Chem. Eng. Data 2009, 54, 2785−2788. (17) Li, Q.; Zhang, J.; Lei, Z.; Zhu, J.; Xing, F. Isobaric Vapor−Liquid Equilibrium for Ethyl Acetate + Ethanol + 1-Ethyl-3-methylimidazolium Tetrafluoroborate. J. Chem. Eng. Data 2009, 54, 193−197. (18) Li, Q.; Zhu, W.; Wang, H.; Ran, X.; Fu, Y.; Wang, B. Isobaric Vapor−Liquid Equilibrium for the Ethanol + Water + 1,3Dimethylimidazolium Dimethylphosphate System at 101.3 kPa. J. Chem. Eng. Data 2012, 57, 696−700. (19) Kato, R.; Krummen, M.; Gmehling, J. Measurement and Correlation of Vapor−Liquid Equilibria and Excess Enthalpies of Binary Systems Containing Ionic Liquids and Hydrocarbons. Fluid Phase Equilib. 2004, 224, 47−54. (20) Li, Q.; Zhang, J.; Lei, Z.; Zhu, J.; Zhu, J.; Huang, X. Selection of Ionic Liquids as Entrainers for the Separation of Ethyl Acetate and Ethanol. Ind. Eng. Chem. Res. 2009, 48, 9006−9012. (21) Calvar, N.; González, B.; Gómez, E.; Domínguez, Á . Vapor− Liquid Equilibria for the Ternary System Ethanol + Water + 1-Ethyl-3methylimidazolium Ethylsulfate and the Corresponding Binary Systems Containing the Ionic Liquid at 101.3 kPa. J. Chem. Eng. Data 2008, 53, 820−825. (22) Döker, M.; Gmehling, J. Measurement and Prediction of Vapor−Liquid Equilibria of Ternary Systems Containing Ionic Liquids. Fluid Phase Equilib. 2005, 227, 255−266. (23) Yao, Y.; Xie, T.; Gao, Y. Handbook of Chemistry and Physics; Shanghai Science and Technology Press: Shangha, China, 1985. (24) Calvar, N.; Gomez, E.; Gonzalez, B.; Dominguez, A. Experimental Vapor−Liquid Equilibria for the Ternary System Ethanol + Water+1-Ethyl-3-methylpyridinium Ethylsulfate and the Corresponding Binary Systems at 101.3 kPa: Study of the Effect of the Cation. J. Chem. Eng. Data 2010, 55, 2786−2791. (25) Orchillés, A. V.; Miguel, P. J.; Vercher, E.; Martínez-Andreu, A. Ionic Liquids as Entrainers in Extractive Distillation Isobaric Vapor− Liquid Equilibria for Acetone + Methanol + 1-Ethyl-3-methylimidazolium Trifluoromethanesulfonate. J. Chem. Eng. Data 2007, 52, 141− 147. (26) Orchillés, A. V.; Miguel, P. J.; Vercher, E.; Martínez-Andreu, A. Isobaric Vapor−Liquid Equilibria for 1-Propanol + Water + 1-Ethyl-3methylimidazolium Trifluoromethanesulfonate at 100 kPa. J. Chem. Eng. Data 2008, 53, 2426−2431. (27) Orchillés, A. V.; Miguel, P. J.; Vercher, E.; Martínez-Andreu, A. Isobaric Vapor−Liquid and Liquid−Liquid Equilibria for Chloroform plus Methanol+1-Ethyl-3-methylimidazolium Trifluoromethanesulfonate at 100 kPa. J. Chem. Eng. Data 2010, 55, 1209−1214. (28) Orchillés, A. V.; Miguel, P. J.; Vercher, E.; Martínez-Andreu, A. Isobaric Vapor−Liquid Equilibria for Methyl Acetate + Methanol + 1Ethyl-3-methylimidazolium Trifluoromethanesulfonate at 100 kPa. J. Chem. Eng. Data 2007, 52, 915−920. (29) Cai, J.; Cui, X.; Zhang, Y.; Li, R.; Feng, T. Vapor−Liquid Equilibrium and Liquid−Liquid Equilibrium of Methyl Acetate + Methanol + 1-Ethyl-3-methylimidazolium Acetate. J. Chem. Eng. Data 2011, 56, 282−287.

The degree of increased temperature relates to the ability of ILs to break the azeotrope. The larger is temperature difference caused by the addition of IL at the same concentration of azeotropy, the less amount of IL is needed for breaking the azeotrope.

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CONCLUSIONS T, x, y data were obtained for the ternary system ethyl acetate (1) + acetonitrile (2) + [BMIM]+[PF6]− (3) at 101.3 kPa. The addition of [BMIM]+[PF6]− to the ethyl acetate + acetonitrile mixture gives a consistent salting-out effect of ethyl acetate over the whole range of the liquid concentrations, and the saltingout effect of [BMIM]+[PF6]− follows the order of x3 ≈ 0.20 > x3 ≈ 0.15 > x3 ≈ 0.10 > x3 ≈ 0.05. At 101.3 kPa, the azeotrope can be eliminated when the mole fraction of [BMIM]+[PF6]− in the liquid phase is greater than 0.05. The VLE data were correlated using the NRTL model with δT of 0.2 K for the ethyl acetate (1) + acetonitrile (2) binary system and of 0.3 K for the ethyl acetate (1) + acetonitrile (2) + [BMIM]+[PF6]− (3) ternary system. The NRTL parameters obtained in this work can be used for the distillation design.

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AUTHOR INFORMATION

Corresponding Author

*Tel: +86 10 64446523. E-mail: [email protected]. Notes

The authors declare no competing financial interest.

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REFERENCES

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dx.doi.org/10.1021/je301204w | J. Chem. Eng. Data 2013, 58, 1112−1116