LiquidâLiquid Equilibrium for Ternary System Methanol + Methyl

Article pubs.acs.org/jced

Liquid−Liquid Equilibrium for Ternary System Methanol + Methyl Acetate + 1,3-Dimethylimidazolium Dimethylphosphate at Several Temperatures and Atmospheric Pressure Fufeng Cai,† Jessica Juweriah Ibrahim,‡ Lei Niu,† Wei Xu,† and Guomin Xiao*,† †

School of Chemistry and Chemical Engineering, Southeast University, Nanjing 211189, P. R. China Beijing Key Laboratory of Membrane Science and Technology & College of Chemical Engineering, Beijing University of Chemical Technology, Beijing 100029, P. R. China

‡

S Supporting Information *

ABSTRACT: The azeotrope methanol and methyl acetate is involved in the industrial manufacturing process of vinyl alcohol which is made from vinyl acetate by alcoholysis with methanol. This work focused on a study of ionic liquid as a solvent in the extraction separation for this azeotropic mixture. The knowledge of liquid−liquid equilibrium (LLE) is essential for the design of the extraction separation process. For this reason, LLE data for the ternary system {methanol + methyl acetate + 1,3-dimethylimidazolium dimethylphosphate ([MMIM][DMP])} were measured at the temperatures T = (298.2, 313.2, and 328.2) K and atmospheric pressure. The consistency of the experimental LLE data was ascertained by using the Othmer-Tobias and Hand equations. Additionally, the experimental LLE data were compared with the correlated values obtained by means of the nonrandom two liquid (NRTL) model. The solute distribution ratios and selectivity values, derived from the experimental LLE data, were calculated and analyzed in order to evaluate the efficiency as a solvent in liquid extraction process. The experimental results show that [MMIM][DMP] can be used as a potential solvent for the separation of methanol and methyl acetate in the liquid−liquid extraction.

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INTRODUCTION For the separation of azeotropic mixtures or those with similar relative volatility in industrial processes, ordinary distillation techniques cannot yield high purity components. Several methods for the separation of azeotropic or close boiling mixtures have been proposed: low temperature crystallization, pressure-swing distillation, azeotropic distillation, extractive distillation, liquid−liquid extraction, membrane separation, and adsorption.1−3 Among these, liquid−liquid extraction, which emerges as a beneficial separation process reducing the energy consumption and the environmental impact, has been widely applied in industry. However, the selection of an efficient and suitable extractive solvent is the key to ensuring a cost-effective operation. Ionic liquids (ILs), a new kind of organic molten salt, have received considerable attention in recent years for their use in liquid extraction separation of alcohols and alkanes, aromatics and alkanes, esters and alcohols, and many other systems4−10 because of their unique properties, such as negligible volatility, thermal stability, and tunable solubility.11,12 Compared to conventional organic solvents, the separation of azeotropic mixtures by using ILs as solvents can offer some advantages: efficient operation process, less energy consumption, and easy regeneration of the solvents. For practical application of ILs in the chemical industry, thermodynamic data are essential for the © 2014 American Chemical Society

analysis and design of the separation processes of azeotropic mixtures. The azeotrope methanol and methyl acetate is present in the industrial manufacturing process of vinyl alcohol which is made from vinyl acetate by alcoholysis with methanol.13 Dohnal et al.14 focused on the separation of the methanol + methyl acetate azeotropic mixture by extractive distillation using the dicyanamide and thiocyanate-based ILs. Dhanalakshmi et al.15 analyzed the effect of bivalent cation inorganic salts on isobaric vapor−liquid equilibrium (VLE) of the methanol + methyl acetate system. Casás et al.16,17 studied the LLE for methanol + methyl acetate + n-alkane at several temperatures and 1 atm. Matsuda et al.18 reported the effect of 1-ethyl-3-methylimidazolium ethyl sulfate on the isothermal VLE data of methanol + methyl acetate. Isobaric VLE and LLE data of the ternary system methanol + methyl acetate + 1-ethyl-3-methylimidazolium acetate ([EMIM][OAc]) was studied by Cui and coworkers.19 Finally, Orchillés et al.20 published the isobaric VLE data for the ternary system methanol + methyl acetate + 1ethyl-3-methylimidazolium trifluoromethanesulfonate at 100 kPa. The ILs with fluorine-substituents can undergo hydrolysis Received: July 18, 2014 Accepted: November 25, 2014 Published: December 4, 2014 57

dx.doi.org/10.1021/je500672d | J. Chem. Eng. Data 2015, 60, 57−64

Journal of Chemical & Engineering Data

Article

Table 1. Sources, Purities, Densities, ρ, and Water Contents by Mass, ww, of the Chemicals Used in This Work at 298.15 K and p = 101.3 kPa ρ/g·cm−3 chemical name

source

mass fraction purity

purification method

exp.

lit.

ww/ 10−6

analysis method

methanol methyl acetate [MMIM][DMP]a

Sinopharm Chemical Reagent Co., Ltd. Sinopharm Chemical Reagent Co., Ltd. prepared in the laboratory

≥ 0.995 ≥ 0.990 ≥ 0.980

desiccation desiccation vacuum desiccation

0.7864b 0.9277b 1.2578b

0.7867c 0.9274c 1.2583d

< 500 < 500 < 500

GCe, KFf GCe, KFf KFf, NMRg

[MMIM][DMP] = 1,3-dimethylimidazolium dimethylphosphate. bStandard uncertainties u are u(ρ) = 0.0002 g·cm−3 and u(T) = 0.01 K. cFrom ref 27. dFrom ref 26. eGas chromatography. fKarl Fischer titration. gNuclear magnetic resonance.

a

magnetic stirrer, and the temperature in the glass cell was measured with a precise and calibrated thermometer with a standard uncertainty of 0.1 K. The sample mixture was stirred vigorously for 2 h in the glass cell and then left to settle for 5 h to ensure a complete split of the equilibrium phases. At the end of the setting period, the samples were obtained from the upper and lower phases using a syringe and compositional analysis was carried out. The compositions of methanol and methyl acetate in the sample were analyzed by gas chromatography. The gas chromatograph (GC-6890, China) was equipped with a flame ionization detector and the capillary column was SE-54 (50 m × 0.32 mm). The carrier gas was high purity nitrogen, and the operating conditions were as follows: both injector and detector temperatures were 473 K, and the oven temperature was 343 K. 1-Butanol was added to the sample as an internal standard substance for the GC analysis and a calibration curve was obtained from a set of gravimetrically prepared standard solutions, which allowed for the quantification of methanol and methyl acetate in the sample. Measurements were carried out in duplicate in order to exclude exceptions in the composition analysis. Each sample was analyzed five times with gas chromatograph. An analytical balance with a standard uncertainty of 0.0001 g was used to weigh the sample. Ternary mixtures with a well-know composition were prepared by mass and were analyzed with the GC. Their compositions were compared with those obtained by mass. The standard uncertainty of the mole fraction of components in the samples was 0.001. Because [MMIM][DMP] has negligible vapor pressure, it cannot be analyzed by GC. The whole of the [MMIM][DMP] was retained by an empty precolumn located between the injector and the chromatographic column. The empty precolumn was periodically cleaned to prevent the [MMIM][DMP] from coming into the capillary column. The [MMIM][DMP] composition in the sample was determined gravimetrically by measuring the mass difference of the liquid sample (∼ 3.5 g) before and after vaporization of the solvents at T = 393 K and under high vacuum (0.2 kPa) until a constant mass was reached. The standard uncertainty of [MMIM][DMP] in the sample was 0.002 in mole fraction. After using the liquid mixtures in the LLE experiments, the solvents were removed by heating and stirring under vacuum (368 K, 0.2 kPa) by a rotary evaporator to recover the used [MMIM][DMP].

producing HF in contact with water and at high temperature. Imidazolium derivates that are phosphorus-containing are promising ILs to be used in industrial processes.21−24 These ILs are not only thermally and chemically stable, have low melting points, and relatively low viscosities but also can be easily synthesized in a halide-free way at a reasonable cost. These merits make them particularly attractive for the separation of methanol and methyl acetate. However, there appears to be no LLE data on the ternary system of methanol + methyl acetate and phosphoric-based ILs. In this work, the LLE data for the ternary system {methanol + methyl acetate + [MMIM][DMP]} were measured at the temperatures T = (298.2, 313.2, and 328.2) K and atmospheric pressure. The consistency of LLE data was ascertained by applying the Othmer-Tobias and Hand equations, and the NRTL model was used to correlate the experimental results for the studied ternary system. Additionally, the capacity of [MMIM][DMP] as a solvent in liquid extraction process was analyzed by the solute distribution ratios and selectivity values. Meanwhile, this capacity was compared with that of other IL from the literature.

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EXPERIMENTAL SECTION Materials. Methanol and methyl acetate were supplied by Sinopharm Chemical Reagent Co., Ltd., China. They were degassed ultrasonically and dried over molecular sieves type 4 Å. Then they were kept in bottles under inert nitrogen atmosphere to avoid moisture. Their purities checked by gas chromatography were 0.995 and 0.990 in mass fraction, respectively. The IL [MMIM][DMP] was synthesized in the laboratory according to the method reported in the literature.25 [MMIM][DMP] was subjected to heating at T = 393 K under high vacuum (0.2 kPa) for 48 h to remove possible traces of solvents and moisture, prior to its use. The mass fraction of water in the [MMIM][DMP], measured by Karl Fischer titration, was xw < 0.0005. The structure of the [MMIM][DMP] was checked by 1H NMR spectrum (Bruker AV-600 spectrometer). Meanwhile, the purity of the IL was verified by contrasting its density at 298.15 K with that of the IL from the literature.26 The specifications of the chemicals used in this work are listed in Table 1. In the Supporting Information, we have described a detailed procedure for the density measurement of the chemicals, and the preparation and characterization of the [MMIM][DMP]. Experimental Procedure and Analysis. LLE experiments were carried out in a 50 mL glass cell containing a magnetic stirrer and thermostated by a water jacket connected to a bath controlled to ± 0.1 K. For the experimental measurements of the LLE data, 20 mL of the [MMIM][DMP] and 10 mL of methanol and methyl acetate mixture corresponding to a two phase region was put into the glass cell and stirred using a

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RESULTS AND DISCUSSION Experimental LLE Data. The LLE data for the ternary system {methanol (1) + methyl acetate (2) + [MMIM][DMP] (3)} at the temperatures T = (298.2, 313.2, and 328.2) K and atmospheric pressure are tabulated in Table 2, where xi represents the mole fraction of component i in the liquid phase. Triangular diagrams of the tie-lines data are displayed in 58



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Table 2. Experimental (Liquid + Liquid) Equilibrium Data for the Ternary System Methanol (1) + Methyl Acetate (2) + [MMIM][DMP] (3) for Mole Fractions, x, at the Temperatures T = (298.2, 313.2, and 328.2) K and p = 101.3 kPa, Together with Solute Distribution Ratios, β, and Selectivity, S, Valuesa upper phase x1

x2

lower phase x3

0.000 0.011 0.027 0.045 0.054 0.062 0.071 0.080 0.089 0.098 0.106 0.114

0.987 0.975 0.958 0.939 0.929 0.919 0.909 0.899 0.889 0.877 0.867 0.858

0.013 0.014 0.015 0.016 0.017 0.019 0.020 0.021 0.022 0.025 0.027 0.028

0.000 0.009 0.017 0.031 0.044 0.053 0.062 0.071 0.085 0.093 0.108 0.116

0.982 0.969 0.959 0.944 0.930 0.919 0.909 0.898 0.882 0.873 0.858 0.849

0.018 0.022 0.024 0.025 0.026 0.028 0.029 0.031 0.033 0.034 0.034 0.035

0.000 0.012 0.027 0.038 0.050 0.066 0.072 0.085 0.093 0.099 0.114 0.121

0.969 0.953 0.935 0.922 0.909 0.891 0.885 0.871 0.860 0.853 0.834 0.824

0.031 0.035 0.038 0.040 0.041 0.043 0.043 0.044 0.047 0.048 0.052 0.055

x1

x2

T = 298.2 0.000 0.211 0.051 0.218 0.098 0.232 0.134 0.254 0.156 0.271 0.171 0.283 0.192 0.305 0.213 0.329 0.228 0.350 0.249 0.382 0.267 0.417 0.283 0.456 T = 313.2 K 0.000 0.229 0.034 0.234 0.055 0.247 0.089 0.262 0.121 0.277 0.143 0.295 0.160 0.316 0.181 0.334 0.206 0.359 0.215 0.388 0.237 0.421 0.248 0.463 T = 328.2.k 0.000 0.242 0.039 0.259 0.075 0.275 0.100 0.287 0.121 0.298 0.147 0.311 0.156 0.334 0.178 0.356 0.193 0.379 0.202 0.417 0.225 0.443 0.234 0.485

x3

β

S

0.789 0.731 0.670 0.612 0.573 0.546 0.503 0.458 0.422 0.369 0.316 0.261

4.64 3.63 2.98 2.89 2.76 2.70 2.66 2.56 2.54 2.52 2.48

20.74 14.99 11.01 9.90 8.96 8.06 7.28 6.51 5.83 5.24 4.67

0.771 0.732 0.698 0.649 0.602 0.562 0.524 0.485 0.435 0.397 0.342 0.289

3.78 3.24 2.87 2.75 2.70 2.58 2.55 2.42 2.31 2.19 2.14

15.64 12.56 10.34 9.23 8.41 7.42 6.85 5.95 5.20 4.47 3.92

0.758 0.702 0.650 0.613 0.581 0.542 0.510 0.466 0.428 0.381 0.332 0.281

3.25 2.78 2.63 2.42 2.23 2.17 2.09 2.08 2.04 1.97 1.93

11.96 9.44 8.45 7.38 6.38 5.74 5.12 4.71 4.17 3.72 3.29

a

Standard uncertainties u are u(T) = 0.1 K, u(p) = 1 kPa, u(x1) = 0.001, u(x2) = 0.001, and u(x3) = 0.002.

Figure 1. Experimental and calculated LLE data in mole fraction for the ternary system methanol (1) + methyl acetate (2) + [MMIM][DMP] (3) at several temperatures and atmospheric pressure: (a) T = 298.2 K; (b) T = 313.2 K; (c) T = 328.2 K. Solid lines and full points represent experimental tie-lines, and dashed lines and empty squares represent calculated data using the NRTL model.

Figure 1. These diagrams provide a visualization of the difference in the size of the immiscibility region, as well as the slopes of the tie-lines for the studied ternary system. As can be observed from Figure 1, the [MMIM][DMP] is completely miscible in the methanol and partial miscible in the methyl acetate, and the size of immiscibility region decreases with increasing of the temperature. This behavior was also reported for other ternary systems involving IL in the literature.28,29 On the other hand, as shown in Figure 1, the positive slopes of the tie-lines indicate that the methanol has a higher affinity toward the [MMIM][DMP] than toward the methyl acetate.

The reliability of experimental LLE data can be ascertained by applying the Othmer-Tobias30 and Hand31 equations: ⎛ 1 − w II ⎞ ⎛ 1 − wI ⎞ 3 2 ⎟ = a + b log⎜ ⎟ log⎜ II I ⎝ w2 ⎠ ⎝ w3 ⎠ 59

(1)



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⎛ w II ⎞ ⎛ wI ⎞ log⎜ 1II ⎟ = c + d log⎜ 1I ⎟ ⎝ w2 ⎠ ⎝ w3 ⎠

(2)

where wI1 and wI2 are the mass fractions of methanol and methyl acetate in the upper (methyl acetate-rich) phase, respectively; w 1II and w 3II are the mass fractions of methanol and [MMIM][DMP] in the lower ([MMIM][DMP]-rich) phase, respectively; a, b, c, and d represent the adjustable parameters. The linearity of this fitting indicates the degree of consistency of the experimental LLE data. The parameters obtained from the Othmer-Tobias and Hand equations are given in Table 3, Table 3. Othmer-Tobias and Hand Equations Parameters, a, b, c, and d, Correlation Factors, R2, and Standard Deviations, σ, for the Ternary System Methanol (1) + Methyl Acetate (2) + [MMIM][DMP] (3) at the Temperatures T = (298.2, 313.2, and 328.2) K and p = 101.3 kPa Othmer-Tobias equation T/K 298.2 313.2 328.2

a

b

0.922 1.452 0.836 1.558 0.836 1.859 Hand equation

R2

σ

0.961 0.935 0.959

0.054 0.064 0.049

T/K

c

d

R2

σ

298.2 313.2 328.2

0.365 0.315 0.243

1.064 1.068 1.061

0.951 0.986 0.976

0.074 0.045 0.052

Figure 3. Hand plot for the ternary system methanol (1) + methyl acetate (2) + [MMIM][DMP] (3) at several temperatures. Experimental data: □, T = 298.2 K; ○, T = 313.2 K; △, T = 328.2 K. Curve fit: solid lines. 2 ⎞1/2 ⎛ ∑ (z exptl − zcalc) ⎜ ⎟ σ=⎜ ⎟ n ⎝ ⎠

(3)

where z and n represent the values and the number of experimental data points, respectively; the subscripts exptl and calc respectively represent the experimental and calculated values; and the summations are extended to the whole range of data points. As shown in Figures 2 and 3, the higher deviations from linearity are obtained for the experimental tie-lines that are present in lower concentration of methanol, when the tielines are closer to the binary system. Similar behaviors were also observed for some authors in studying ternary systems containing IL.32,33 The experimental data in this work are reliable which can be inferred from the values of R2 and σ presented in Table 3. To evaluate the extraction capacity of [MMIM][DMP] as a solvent, together with the LLE data, the solute distribution ratio and selectivity are also displayed in Table 2. The solute distribution ratio, β, and selectivity, S, are defined as follows:

together with the correlation factor, R2, and standard deviations for the studied ternary system. The Othmer-Tobias and Hand plots for the studied ternary system are shown in Figures 2 and 3, respectively. The standard deviation, σ, was calculated by applying the following equation:

β=

S=

x1II x1I

(4)

x1IIx 2I x1Ix 2II

(5)

where xI1 and xI2 are the mole fractions of methanol and methyl acetate in the upper (methyl acetate-rich) phase, respectively; and xII1 and xII2 are the mole fractions of methanol and methyl acetate in the lower ([MMIM][DMP]-rich) phase, respectively. The variations of the solute distribution ratio and selectivity for the studied ternary system with the composition of methanol in the upper phase are presented in Figures 4 and 5, respectively. These figures show the solute distribution ratios and selectivity values decrease with increasing composition of methanol in the upper phase for the studied ternary system. This behavior is in agreement with other authors in studying different azeotropic mixtures with ILs.34−36 As can be seen from Figure 5, the selectivity values for the studied ternary system are

Figure 2. Othmer-Tobias plot for the ternary system methanol (1) + methyl acetate (2) + [MMIM][DMP] (3) at several temperatures. Experimental data: □, T = 298.2 K; ○, T = 313.2 K; △, T = 328.2 K. Curve fit: solid lines. 60



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and [EMIM][OAc] in the system methanol and methyl acetate is likely to be related to the divergent Kamlet−Taft solvent parameters including the hydrogen-bond acidity, the hydrogenbond basicity, and the polarity/polarizability.37 The Kamlet− Taft parameters were proven to be effective for representing the bulk solvent strength.38,39 The cation of IL is responsible for the hydrogen-bond acidity value, and the hydrogen-bond basicity value is mainly dependent on the anion of IL. The imidazolium IL with acetate anion (1.201) has a higher hydrogen-bond basicity value than the studied phosphoricbased IL (1.118), which may lead to methanol being more soluble in the [EMIM][OAc].40 Thus, it can be understood that the higher extraction capacity was found in the system methanol + methyl acetate + [EMIM][OAc]. The variation of solute distribution ratio and selectivity was correlated by an exponential equation with three adjustable parameters and having a good degree of accuracy in the published studies.28,33,41 The equations are listed as follows: β = E + F exp( −x1I/G)

Figure 4. Solute distribution ratio, β, as a function of the mole fraction of methanol in the upper phase, xI1, for the ternary system methanol (1) + methyl acetate (2) + [MMIM][DMP] (3) at several temperatures and atmospheric pressure. Experimental data: □, T = 298.2 K; ○, T = 313.2 K; △, T = 328.2 K. The solid lines represent the calculated data using eq 6.

(6)

S = e + f exp( −x1I/g )

(7)

xI1

where E, F, G, e, f, and g represent adjustable parameters; is the mole fractions of methanol in the upper phase. These parameters together with the standard deviations are given in Table 4. The comparisons between the experimental and Table 4. Adjustable Parameters, E, F, G, e, f, and g, of eqs 6 and 7, and Standard Deviations, σ, for the Ternary System Methanol (1) + Methyl Acetate (2) + [MMIM][DMP] (3) at the Temperatures T = (298.2, 313.2, and 328.2) K and p = 101.3 kPa T/K

E

F

G

σ

298.2 313.2 328.2 T/K

2.482 2.138 1.934 e

3.628 2.136 2.199 f

0.024 0.036 0.032 g

0.052 0.106 0.067 σ

298.2 313.2 328.2

4.671 3.920 3.286

27.092 16.467 14.595

0.031 0.037 0.037

0.397 0.344 0.272

calculated data are plotted in Figures 4 and 5, respectively. As displayed in Figures 4 and 5, the equations can successfully correlate the solute distribution ratios and selectivity values. Thermodynamic Correlation. The NRTL42 model was employed to correlate the LLE data for the studied ternary system. This model has provided adequate correlating capability for the ternary system involving IL in LLE/VLE data.43−47 The activity coefficients in multicomponent systems were calculated by the NRTL model:

Figure 5. Selectivity, S, as a function of the mole fraction of methanol in the upper phase, xI1, for the ternary system methanol (1) + methyl acetate (2) + [MMIM][DMP] (3) at several temperatures and atmospheric pressure. Experimental data: □, T = 298.2 K; ○, T = 313.2 K; △, T = 328.2 K; ■, T = 299.2 K, from ref 19. The solid lines represent the calculated data using eq 7.

m

greatly higher than the unity, especially at low methanol composition. Therefore, it can be inferred that the [MMIM][DMP] could be considered act to as a solvent for the extraction separation of methanol and methyl acetate, adding the easiness of recovery of [MMIM][DMP]. The comparison of the selectivity values for the studied ternary system with that from the literature19 was also displayed in Figure 5. It can be observed that the values of selectivity for [MMIM][DMP] were lower than that of the [EMIM][OAc]. The distinction of extraction capacity for the [MMIM]DMP]

ln γi =

∑ j = 1 τjiGjixj m

∑l = 1 Glixl

m

+

∑ j=1

m ⎛ ∑r = 1 xrτrjGrj ⎞ ⎜ ⎟ τ − ij m m ∑l = 1 Gljxl ⎟⎠ ∑l = 1 Gljxl ⎜⎝

xjGij

(8)

where Gij = exp( −αijτij)

τij = 61

(9)

Δgij RT

(10) dx.doi.org/10.1021/je500672d | J. Chem. Eng. Data 2015, 60, 57−64


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where xi is the mole fraction of component i in the liquid phase; αij is nonrandomness parameter; Δgij is binary interaction parameter; and T is temperature. For the studied ternary system {methanol (1) + methyl acetate (2) + [MMIM][DMP] (3)}, the 1−2 binary methanolmethyl acetate parameters of the NRTL model were obtained from the literature.19 The 1−3 and 2−3 binary parameters of the NRTL model were obtained by using the LLE data in Table 2 through the minimization of the objective function (OF): OF =

exptl and calc represent the experimental and calculated values, respectively; and the summations are extended to the whole range of data points. From the value of δ shown in Table 5, it can be inferred that the NRTL model can correlate the experimental data with a good degree of accuracy. For a visual confirmation the experimental tie-lines and those calculated with the NRTL model are displayed in Figure 1, where the good of the correlations can also be confirmed.

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CONCLUSIONS In this work, experimental LLE data for the ternary system {methanol (1) + methyl acetate (2) + [MMIM][DMP] (3)} were measured at the temperatures T = (298.2, 313.2, and 328.2) K and atmospheric pressure. The reliability of the LLE data was ascertained by using the Othmer−Tobias and Hand equations, and the NRTL model can be used to correlate the experimental LLE data with a good accuracy. From the experimental LLE data, the corresponding values of the solute distribution ratio and selectivity were calculated. The values of solute distribution ratio and selectivity for the studied ternary system decrease when the methanol composition in the upper phase increases. Additionally, the extraction effectiveness for the [MMIM][DMP] decreases with increasing of the temperature. The selectivity values are greatly higher than unity for the studied ternary system, which confirms that the [MMIM][DMP] is suitable for use as a potential solvent for the separation of methanol and methyl acetate in the liquid−liquid extraction. Meanwhile, the high solute distribution ratios are obtained, which mean that a lower amount of the [MMIM][DMP] would be required in the extraction process.

∑ [(x1Ιi − x1Ιi(calc))2 + (x2Ιi − x2Ιi(calc))2 + (x1IIi − x1IIi (calc))2 + (x 2IIi − x 2IIi (calc))2 ]

xI1i,

(11)

xI2i, xII1i, and xII2i are the xI2i(calc), xII1i(calc), and

where experimental mole fraction; xI1i(calc), xII2i(calc) are the calculated mole fraction; and superscripts I and II represent the upper and lower phases, respectively; and the summations are extended to the whole range of data points. During the regression of the NRTL model parameters, the equality of the activity for each component in both phases was assumed. With the assumption of equilibrium in the liquid phase, the referring equation is xiΙ =

γi II γi Ι

xiII (12)

where xIi and xIIi are the mole fraction of component i in the upper and lower phases, respectively; γIi and γIIi are the activity coefficient of component i in the upper and lower phases, respectively. The NRTL model parameters for the studied ternary system are presented in Table 5, as well as the root-mean-square

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* Supporting Information

Table 5. Nonrandomness Factors, αij, Binary Interaction Parameters, Δgij and Δgji, and Root Mean Square Deviation, δ, Obtained from the Correlation of the Experimental Liquid−Liquid Equilibrium Data of the Ternary System {Methanol + Methyl Acetate + [MMIM][DMP]} by the NRTL Model at the Temperatures T = (298.2, 313.2, and 328.2) K and p = 101.3 kPa i component

j component

methanol (1)

methyl acetate (2) [MMIM] [DMP] (3) [MMIM] [DMP] (3)

methanol (1) methyl acetate (2) a

αij

−1

−1

ASSOCIATED CONTENT

S

Detailed procedure for the density measurement of the chemicals and the preparation and characterization of the [MMIM][DMP]. This material is available free of charge via the Internet at http://pubs.acs.org.

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AUTHOR INFORMATION

Corresponding Author

*Tel.: +86-25-5209-0612. Fax: +86-25-5209-0612. E-mail: [email protected].

Δgij/J·mol

Δgji/J·mol

δ

0.296a

1857.4a

1214.9a

0.294

253.9

−521.3

This work was financially supported by the National Natural Science Foundation of China (No. 21276050 and 21076044). The authors gratefully acknowledge these grants.

0.127

10160.3

−987.4

Notes

0.0063

Funding

The authors declare no competing financial interest.

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From ref 19.

(1) Seiler, M.; Jork, C.; Kavarnou, A.; Arlt, W.; Hirsch, R. Separation of Azeotropic Mixtures Using Hyperbranched Polymers or Ionic Liquids. AIChE J. 2004, 50, 2439−2454. (2) Bürst, W.; Kaibel, G.; Kuntze, T.; Konig, J. U.S. Patent No.0130077A1, 2002. (3) Dussel, R.; Stichlmair, J. Separation of Azeotropic Mixtures by Batch Distillation Using an Entrainer. Comput. Chem. Eng. 1995, 19, 113−118. (4) Pereiro, A. B.; Rodríguez, A. Effective Extraction in Packed Column of Ethanol from the Azeotropic Mixture Ethanol + Hexane with an Ionic Liquid as Solvent. Chem. Eng. J. 2009, 153, 80−85. (5) Garcia-Chavez, L. Y.; Schuur, B.; de Haan, A. B. Liquid−Liquid Equilibrium Data for Mono Ethylene Glycol Extraction from Water

deviation between the experimental and calculated values of liquid phase mole fraction. The root-mean-square deviation for the experimental values and calculated values obtained by means of NRTL model was calculated by using the following equation: exptl calc 2 δ = (∑ (xilm − xilm ) /6k)1/2

REFERENCES

(13)

where x is the mole fraction; the subscripts i, l, and m represent the component, the phase and the tie-lines, respectively; k represents the number of experimental tie-lines; superscripts 62



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