J. Chem. Thermodynamics 141 (2020) 105932
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Liquid-liquid equilibrium measurements and interaction exploration for separation of isobutyl alcohol + isobutyl acetate by imidazolium-based ionic liquids with different anions Xianglin Meng a, Rui Li a, Xiaobin Bing a, Jun Gao a, Dongmei Xu a,⇑, Lianzheng Zhang a, Yinglong Wang b a b
College of Chemical and Environmental Engineering, Shandong University of Science and Technology, Qingdao 266590, China College of Chemical Engineering, Qingdao University of Science and Technology, Qingdao 266042, China
a r t i c l e
i n f o
Article history: Received 23 July 2019 Received in revised form 13 August 2019 Accepted 1 September 2019 Available online 4 September 2019 Keywords: Liquid-liquid equilibrium Ionic liquids Isobutyl acetate Isobutyl alcohol Extraction
a b s t r a c t For separation of the azeotropic mixture isobutyl alcohol and isobutyl acetate, liquid-liquid extraction was adopted in this work and three imidazolium-based ionic liquids with different anions 1-butyl-3methylimidazolium dihydrogen phosphate ([Bmim][H2PO4]), 1-butyl-3-methylimidazolium hydrogen sulfate ([Bmim][HSO4]) and 1-butyl-3-methylimidazolium methyl sulfate ([Bmim][MeSO4]) were chosen as extractants. The liquid – liquid equilibrium data (LLE) for isobutyl alcohol + isobutyl acetate + ([Bmim] [H2PO4]/[Bmim][HSO4]/[Bmim][MeSO4]) were determined at 298.15 K and 101.3 kPa. The distribution coefficient and selectivity were calculated to evaluate extraction capability of the selected extractants. Furthermore, the r-profiles and interaction energies based on conductor-like screening segment activity coefficient model (COSMO-SAC) were calculated to provide theoretical insight to interactions among the components. Also, the measured LLE data was correlated by the NRTL model and binary interaction parameters were regressed which is helpful for the separation process design and optimization. Ó 2019 Elsevier Ltd.
1. Introduction Isobutyl acetate (IBAC) is an important chemical, which can be applied for production of coatings, inks, degreasers and pharmaceuticals [1,2]. Usually, isobutyl acetate can be prepared by esterification with acetic acid and isobutyl alcohol (IBA). However, during the preparation, the product IBAC and unreacted reactant IBA can form an azeotrope . Therefore, it is difficult to purify IBAC by conventional distillation. In industry, for separating such azeotropic mixtures, special distillation technologies are required, such as extractive distillation [4–8], azeotropic distillation , pressure-swing distillation [10,11]. Generally, liquid-liquid extraction can be considered as an alternative to separate the azeotropic mixture due to its energy-savings and high separation efficiency [12–15]. In this work, liquid-liquid extraction was adopted to separate the azeotropic mixture IBA + IBAC using ionic liquids (ILs), since ionic liquids has many excellent properties such as thermal stability, easy recoverability, simplicity and environment friendly [16–22]. Recently, many researchers explored the separation of azeotropes by liquid-liquid extraction [23,24] and measured the ⇑ Corresponding author. E-mail address: [email protected]
(D. Xu). https://doi.org/10.1016/j.jct.2019.105932 0021-9614/Ó 2019 Elsevier Ltd.
ternary liquid-liquid equilibrium data containing ILs [25–28]. Xu et al.  reported the separation of propyl acetate and butyl acetate from the azeotropes of (propanol + propyl acetate) and (butanol + butyl acetate) using the ILs with different alkyl chain cation and anion [PF 6 ]. Pereiro et al.  adopted ILs to separate azeotrope of (ethyl acetate + isopropanol) and determined the LLE data for the system with different ILs. Liu et al.  reported the extraction of isopropanol from its aqueous solution using imidazolium ionic liquids with anion of [NTf2] as extractants. Meng et al.  measured the ternary liquid-liquid equilibrium (LLE) data for IBAC + IBA + ([Hmim][PF 6 ]/[Omim][PF6 ]) at different temperature and explored the effect of cations. The results showed that the shorter of the cations of ILs, the better the extraction is. Based on above, three ionic liquids with different anions [Bmim][HSO4], [Emim][MeSO4] and [Bmim][H2PO4] were chosen as extractants to separate the azeotrope IBA and IBAC. So, the LLE data for the mixtures (IBA + IBCA + ILs) was determined at 298.15 K and 101.3 kPa for designing and optimizing the separation process. Meanwhile, to evaluate the extraction capacity of the ILs, the selectivity and distribution coefficient were calculated. The NRTL model  was applied to correlate the measured LLE data. In addition, to explore the interactions between ILs and IBAC/ IBA, the r-profiles and interaction energies were calculated [34,35].
X. Meng et al. / J. Chem. Thermodynamics 141 (2020) 105932 Table 2 The names and structures of cation and anions.
2. Experiment 2.1. Chemicals IBAC and IBA were purchased from Shanghai Macklin Biochemical Co., Ltd. The ionic liquids were provided by Lanzhou Zhongke Ketko Industry & Trade Co. Ltd. To ensure the purity of the ionic liquids in experiments, the ILs were all dried in a vacuum drying oven at 363.15 K under 20 kPa to remove the moisture . The information of chemicals is presented in Table 1. The structures of cation and anions of the relevant ILs are presented in Table 2.
2.2. Apparatus and procedure
The LLE measurements for the ternary mixtures (IBA + IBAC + ILs) were performed at 298.15 K under 101.3 kPa. The experimental apparatus and detailed procedures were presented in our previous work . To ensure the whole two-phase region be covered as possible, during the preparation of the feed mixture, the IL mass was kept constant, the mass of IBA decreased and the mass of IBAC increased gradually. After that, the mixture was placed into a round-bottom flask, which was stirred vigorously for at least 5 h by a magnetic stirrer in a water bath (DF-101S, Changzhou Guoyu instrument Manufacturing Co., Ltd.). Then, the mixture was settled for 18 h to reach the equilibrium state. At last, the upper and lower liquid phases was taken out carefully by syringes and each sample was detected by GC.
Figs. 1–3, the selected ILs are all partially soluble with IBAC and completely soluble with IBA, which indicates the ILs have affinity with IBA compared to IBAC. 3.2. Distribution coefficient and selectivity
2.3. Analysis Gas chromatography (Lunan GC SP-6890) was applied to analyse the composition of all samples from the upper and lower phases using a packed column (Porapak Q 3 mm 2 m). In addition, a thermal conductivity detector was adopted, which was presented in our previous work . Hydrogen gas with purity of 99.999 wt% was used as carrier gas for GC. The area correction normalization method was applied for analysis, which has been described in the literature . The operation temperature of oven, injector and detector were set to 448.15 K, 443.15 K and 453.15 K. Due to the non-volatility of ILs, the content of ILs cannot be detected by GC. In this work, the content of the ILs weight was determined by gravimetric method (AR124CN, Changzhou Aohaosi, China), which was calculated the sample mass difference before and after drying the samples in a vacuum drying oven (DZF6050, Shanghai Yiheng, China). 3. Results and discussion 3.1. Experimental results The experiments of ternary liquid-liquid equilibrium for (IBA + IBAC + ILs) were performed at temperature of 298.15 K under 101.3 kPa. The experimental results are listed in Table 3 and presented in Figs. 1–3, which belong to Treybal’s type I . From
For liquid-liquid extraction process, distribution coefficient (D) and selectivity (S) are important indicators for evaluating the extractant performance of selected ILs. The expressions for distribution coefficient and selectivity are presented in Eqs (1) and (2): [38–41]
xII1 =xI1 xII2 =xI2
where xI1 and xII1 are the mole fractions for IBA in IBAC-rich phase and IL-rich phase; xI2 and xII2 stand for the mole fraction for IBAC in IBAC-rich phase and IL-rich phase. As can be seen in Table 3, the values of distribution coefficient for the system (IBA + IBAC + [Bmim][H2PO4]/[Bmim][MeSO4]) are all larger than unity except for [Bmim][HSO4], which implies that a smaller amount of the extractants [Bmim][H2PO4] and [Bmim] [MeSO4] is required compared to [Bmim][HSO4] [32,42,43]. Meanwhile, the calculated selectivity values for the systems are larger than unity, which indicates the selected ILs are able to extract IBA from the azeotropic mixture. The larger value of S, the stronger extraction ability is. To compare the extraction performance for the different ILs, the selectivity versus IBA mole fraction in IBAC-rich
Table 1 Detailed information of chemicals.
Isobutyl acetate Isobutyl alcohol [Bmim][HSO4] [Bmim][MeSO4] [Bmim][H2PO4]
110-19-0 78-83-1 262297-13-2 262297-13-2 478935-31-8
Shanghai Macklin Biochemical Co., Ltd Shanghai Macklin Biochemical Co., Ltd Lanzhou Zhongke Ketko Industry & Trade Co. Ltd. Lanzhou Zhongke Ketko Industry & Trade Co. Ltd. Lanzhou Zhongke Ketko Industry & Trade Co. Ltd.
– – 967b 860b 898b
0.997a 0.995a 0.990a 0.990a 0.990a
Analyzed by the suppliers. Determined by KLS701 Micro-moisture Meter.
X. Meng et al. / J. Chem. Thermodynamics 141 (2020) 105932 Table 3 Composition (mole fraction) of the Experimental Tie-Lines, IBA Distribution Coefficient (D), and Selectivity (S) for Ternary Systems at T = 298.15 K under 101.3 kPa.a Upper phase xI1
Lower phase xI2
0.2830 0.2589 0.2272 0.1961 0.1761 0.1620 0.1527 0.1401
1.032 1.075 1.097 1.116 1.148 1.186 1.220 1.247
1.949 2.461 3.108 3.933 4.827 5.746 6.685 7.929
0.3116 0.2577 0.2194 0.1704 0.1192 0.0915 0.0671 0.0350
0.4283 0.3994 0.3706 0.3500 0.3311 0.3004 0.2740 0.2461
1.702 1.619 1.594 1.473 1.401 1.289 1.217 1.209
3.208 3.374 3.682 3.706 3.864 3.980 4.194 4.769
0.4835 0.4144 0.3425 0.2853 0.2318 0.1855 0.1272 0.0878 0.0472
0.2604 0.2431 0.2193 0.2062 0.1996 0.1897 0.1760 0.1607 0.1510
1.010 0.962 0.906 0.874 0.824 0.808 0.784 0.769 0.741
1.901 2.169 2.525 2.830 2.950 3.269 3.721 4.232 4.590
IBA (1) + IBAC (2) + [Bmim][H2PO4] (3) 0.4379 0.5344 0.3926 0.5927 0.3520 0.6438 0.3052 0.6909 0.2577 0.7402 0.2138 0.7850 0.1630 0.8368 0.1090 0.8909
0.4520 0.4221 0.3860 0.3407 0.2960 0.2535 0.1988 0.1358
IBA (1) + IBAC (2) + [Bmim][MeSO4] (3) 0.1831 0.8073 0.1592 0.8326 0.1377 0.8565 0.1157 0.8806 0.0851 0.9129 0.0710 0.9278 0.0552 0.9440 0.0289 0.9707 IBA (1) + IBAC (2) + [Bmim][HSO4] (3) 0.4787 0.4901 0.4309 0.5483 0.3783 0.6115 0.3265 0.6677 0.2813 0.7147 0.2297 0.7677 0.1623 0.8357 0.1142 0.8848 0.0637 0.9360
Standard uncertainties: u(T) = 0.05 K, u(p) = 0.52 kPa, and u(x) = 0.0067.
Fig. 1. Tie-lines for ternary system IBA (1) + IBAC (2) + [Bmim][H2PO4] (3) at T = 298.15 K: (j - j), experimental data; (s – s), correlated by the NRTL model.
phase was plotted in Fig. 4. From the Fig. 4, [Bmim][H2PO4] is the suitable extractant compared to the other two ILs. 4. Interaction exploration 4.1. r-Profiles analysis For analysis of the interaction of the components in the mixture, the r-profiles for the components were calculated by conductor-like screening model (COSMO-SAC) [34,44–46]. The detailed calculation procedures were presented in our previous work . The r-profiles for IBA, IBAC and different
Fig. 2. Tie-lines for ternary system IBA (1) + IBAC (2) + [Bmim][MeSO4] (3) at T = 298.15 K: (j - j), experimental data; (s – s), correlated by the NRTL model.
ILs anions [HSO4], [MeSO4], [H2PO4]) were calculated and are presented in Fig. 4. As shown in Fig. 4, there are two vertical dash lines (r = ±0.0084 e/Å2), which divides the whole zone into three areas. The left area (r < 0.0084 e/Å2) belongs to the hydrogen bond donor zone. Surface segment in this zone has better hydrogen bond donator ability. Similarly, the right area (r > +0.0084 e/Å2) is hydrogen bond acceptor zone. And the area between these two dash lines is neutral zone. In the hydrogen donor or acceptor zone, the farther the peak in profiles away from r = 0.0084 e/Å2 or 0.0084 e/Å2, the stronger the hydrogen bond donator or acceptor ability is.
X. Meng et al. / J. Chem. Thermodynamics 141 (2020) 105932
Fig. 3. Tie-lines for ternary system IBA (1) + IBAC (2) + [Bmim][HSO4] (3) at T = 298.15 K: (j - j), experimental data; (s – s), correlated by the NRTL model.
Therefore, in Fig. 5, IBAC has the r-profile from 0.009 eÅ2 to 0.015 eÅ2 and there is a peak at 0.011 eÅ2, which indicates that isobutyl acetate only has hydrogen bond acceptor ability. However, the r-profile of IBA not only exists in hydrogen donor zone, but also in hydrogen acceptor zone. Thus, IBA has hydrogen bond donor and acceptor ability compared to IBAC. For the different anions ([HSO4], [MeSO4], [H2PO4]), the r-profiles indicate they have both the ability of hydrogen bond donor and hydrogen bond receptor. However, the largest peaks of the anions are located within the hydrogen bond acceptor zone. This indicates that they have stronger hydrogen bond acceptor ability. Hence, the anions form hydrogen bonds more easily with IBA than IBAC. Compared to [HSO4] and [MeSO4], the peak of [H2PO4] is shifted more from the right vertical dash line (r = +0.0084 eÅ2), which implies that hydrogen bond acceptor ability for [H2PO4] is the strongest among these anions. Owing to the similar peak locations of [HSO4] and [MeSO4] in the hydrogen bond acceptor zone, the anions [HSO4] and [MeSO4] have similar acceptor ability. Based on the above, the IL [Bmim][H2PO4] is more favouable for the separation of IBA and IBAC compared to other two ILs. 4.2. Interaction energy calculation To calculate the interaction energies between ionic liquids and IBA/IBAC, the Dmol3 module incorporated with the density functional theory was applied [13,38,47]. The counterpoise correction method  was employed to correct the Basis Set Superposition Error (BSSE). The interaction energy can be calculated by Eqs (3) and (4) was employed and is expressed as follows:
Fig. 4. Selectivity (S) on mole fraction for IBA in IBAC-rich phase (xI1 ):(▲) [Bmim] [H2PO4]; ( ) [Bmim][HSO4]; ( ) [Bmim][MeSO4].
DEinteraction ¼ EAB EA EB þ EBSSE
EBSSE ¼ EA EðA;ABÞ þ EB EðB;ABÞ
where EAB refers to the energy of the complex of AB in the A; B basis set, EA and EB are the energy of A in the A basis set and B in the B basis set, respectively. Similarly, EðA;ABÞ and EðB;ABÞ represent the energy of A in the A; B basis set and B in the A; B basis set, respectively. The optimized geometric structures for ILs with IBA are shown in Fig. 6 and the calculation results for interaction energies are listed in Table 4. From Table 4, the calculated interaction energies for [Bmim] [H2PO4], [Bmim][HSO4], [Bmim][MeSO4] with IBA are 38.1259, 24.9604, 24.7057 kJ mol1, respectively, which means the selected ILs have stronger attraction with IBA. This can explain why the selected ILs are able to extract IBA from the mixture of IBA and IBAC. In addition, the value of interaction energy between [Bmim][H2PO4] and IBA is greatest compared to the other two ILs, which indicates that [Bmim][H2PO4] is the best extractant to separate the azeotropic mixture IBA and IBAC. 5. Data correlation For correlation of the measured LLE tie-line data , the NRTL model [33,50] was adopted and is presented as follows:
P P X xj Gij xs G j sji Gji xj P Lnci ¼ P þ sij Pl l lj lj k Gki xk k Gkj xk k Gkj xk j
Gij ¼ exp aij sij Fig. 5. r-Profiles for IBA, IBAC, and anions ([HSO4], [MeSO4], [H2PO4]).
where i and j refer to the component in the system; ci is activity coefficient for component i; Dgij is the binary interaction parameter
X. Meng et al. / J. Chem. Thermodynamics 141 (2020) 105932
Fig. 6. Optimized geometric structures for systems IBA + ILs: [Bmim][H2PO4] (a); [Bmim][HSO4] (b); [Bmim][MeSO4] (c).
To evaluate the correlated results, the root mean square deviation (RMSD) [53–55] was adopted and is defined as follows:
Table 4 Calculation results for interaction energies between ILs and IBA/IBAC. E/(hartreea)
System IBAC IBA [Bmim][H2PO4] [Bmim][HSO4] [Bmim][MeSO4] [Bmim][H2PO4] + IBA [Bmim][H2PO4] + IBAC [Bmim][HSO4] + IBA [Bmim][HSO4] + IBAC [Bmim][MeSO4] + IBA [Bmim][MeSO4] + IBAC a
386.4360 273.0411 1067.2436 1123.3695 1162.6754 1340.3186 1453.7055 1396.4391 1509.8302 1435.7454 1549.1363
2 31=2 P3 P2 PM exp cal x x i¼1 j¼1 k¼1 ijk ijk 6 7 RMSD ¼ 4 5 6M
10.147 10 7.1694 105 2.8023 106 2.9497 106 3.0529 106 3.5193 106 3.8171 106 3.6667 106 3.9644 106 3.7699 106 4.0676 106
– – – – – 38.1259 4.4927 24.9604 7.6593 24.7057 6.8637
The obtained interaction parameters and the values of RMSD are listed in Table 5. As shown in Table 5, the NRTL model can correlate the measured LLE values with the value of RMSD less than 0.025. The correlated results are also presented in Figs. 1–3 for comparison.
1 hartree = 2625.753 kJmol1.
between component i and j, ; aij is the non-random parameter and was set to 0.3. In this work, the parameters of the NRTL model for the systems were determined by minimizing the deviations between experimental and calculated compositions . The expression of the objective function (OF)  is defined as follows:
OF ¼ min
M X 2 X 3 2 X cal xexp ijk xijk k¼1 j¼1
where M stands for the number of experimental points; xexp and xcal represent the experimental values and calculated results; i, j and k denote the component, phase and tie-line.
In this work, for separation the azeotropic mixture IBA and IBAC by liquid-liquid extraction, three ILs [Bmim][H2PO4], [Bmim] [HSO4] and [Bmim][MeSO4] were selected as the extractants. The liquid-liquid equilibrium data for the mixtures (IBA + IBAC + [Bmim][H2PO4]), (IBA + IBAC + [Bmim][HSO4]) and (IBA + IBAC + [Bmim][MeSO4]) were determined at 298.15 K and 101.3 kPa, respectively. Based on experimental data, the distribution coefficient and selectivity were calculated. The values of selectivity are all greater than unity, which indicates the selected ILs as extractants for separating the azeotrope mixture IBA and IBAC are feasible. In addition, by comparing extraction performance of the three ILs, [Bmim][H2PO4] is suitable as extractant to separate the azeotropic mixture IBA and IBAC. Moreover, the r-profiles and interaction energies were calculated to explore the interaction between IBA and ILs. The NRTL model was used to correlate the LLE data
Table 5 Values of binary interaction parameters of NRTL and RMSD.
7.6432 12.6207 9.0681
IBA (1) + IBAC (2) + [Bmim][MeSO4] (3) 1–2 3.9976 1–3 3.1066 2–3 21.3986
23.0385 14.5567 5.0606
IBA (1) + IBAC (2) + [Bmim][HSO4] 1–2 1–3 2–3
6.7621 7.0783 16.4869
Binary interaction parameters
IBA (1) + IBAC (2) + [Bmim][H2PO4] 1–2 1–3 2–3
(3) 4.0065 12.6207 29.0453
(3) 4.8179 7.1355 22.2963
X. Meng et al. / J. Chem. Thermodynamics 141 (2020) 105932
and the binary interaction parameters were regressed with the values of RMSD less than 0.025, which indicates the NRTL model can correlate well the measured LLE data. Acknowledgements This work was supported by the National Natural Science Foundation of China (Grant 21878178), Shandong Provincial Key Research & Development Project (2018GGX107001) and A Project of Shandong Province Higher Educational Science and Technology Program (J18KA072). Note The authors declare no competing financial interest. References  R. Muñoz, J.B. Montón, M.C. Burguet, J. de la Torre, Separation of isobutyl alcohol and isobutyl acetate by extractive distillation and pressure-swing distillation: simulation and optimization, Sep. Purif. Technol. 50 (2006) 175– 183.  A. Cháfer, J. de la Torre, J.B. Monton, E. Lladosa, Liquid–liquid equilibria of the systems isobutyl acetate+isobutyl alcohol+water and isobutyl acetate+isobutyl alcohol+glycerol at different temperatures, Fluid Phase Equilib. 265 (2008) 122–128.  J.B. Montón, R. Muñoz, M.C. Burguet, J.d.l. Torre, Isobaric vapor–liquid equilibria for the binary systems isobutyl alcohol+isobutyl acetate and tertbutyl alcohol+tert-butyl acetate at 20 and 101.3kPa, Fluid Phase Equilib. 227 (2005) 19–25.  Y. Zhang, K. Liu, Z. Wang, J. Gao, L. Zhang, D. Xu, Y. Wang, Vapour–liquid equilibrium and extractive distillation for separation of azeotrope isopropyl alcohol and diisopropyl ether, J. Chem. Thermodyn. 131 (2019) 294–302.  Y. Zhao, K. Ma, W. Bai, D. Du, Z. Zhu, Y. Wang, J. Gao, Energy-saving thermally coupled ternary extractive distillation process by combining with mixed entrainer for separating ternary mixture containing bioethanol, Energy 148 (2018) 296–308.  Z. Lei, C. Li, B. Chen, Extractive distillation: a review, Sep. Purf. Rev. 32 (2003) 121–213.  W. Li, B. Xu, Z. Lei, C. Dai, Separation of benzene and cyclohexane by extractive distillation intensified with ionic liquid, Chem. Eng. Process. 126 (2018) 81–89.  Z. Lei, C. Dai, J. Zhu, B.J.A.J. Chen, Extractive distillation with ionic liquids: a review, AICHE J. 60 (2014) 3312–3329.  P. Shi, Y. Gao, J. Wu, D. Xu, J. Gao, X. Ma, Y. Wang, Separation of azeotrope (2,2,3,3-tetrafluoro-1-propanol + water): isobaric vapour-liquid phase equilibrium measurements and azeotropic distillation, J. Chem. Thermodyn. 115 (2017) 19–26.  S. Liang, Y. Cao, X. Liu, X. Li, Y. Zhao, Y. Wang, Y. Wang, Insight into pressureswing distillation from azeotropic phenomenon to dynamic control, Chem. Eng. Res. Des. 117 (2017) 318–335.  W.L. Luyben, Pressure-swing distillation for minimum- and maximum-boiling homogeneous azeotropes, Ind. Eng. Chem. Res. 51 (2012) 10881–10886.  P. Wang, P. Yan, J.A. Reyes-Labarta, J. Gao, D. Xu, L. Zhang, Y. Wang, Liquidliquid measurement and correlation for separation of azeotrope (dimethyl carbonate and ethanol) with different imidazolium-based ionic liquids, Fluid Phase Equilib. 485 (2019) 183–189.  D. Sun, H. Feng, F. Xin, W. Li, Z. Zhang, Screening of ionic liquids as extractant for 1-butanol extraction from dilute solution, J. Taiwan Inst. Chem. E 91 (2018) 119–129.  H.G. Gilani, A. Ghanadzadeh Gilani, S.L. Seyed Saadat, Experimental and correlational study of phase equilibria in aqueous solutions of formic and butyric acids with isoamyl acetate and methyl isoamyl ketone at T = 298.15 K, J. Chem. Eng. Data 59 (2014) 917–925.  A. Ghanadzadeh Gilani, H. Ghanadzadeh Gilani, S. Shekarsaraee, E. NasiriTouli, S.L. Seyed Saadat, Liquid–liquid equilibria study of the (water +phosphoric acid+hexyl or cyclohexyl acetate) systems at T=(298.15, 308.15, and 318.15)K: measurement and thermodynamic modelling, J. Chem. Thermodyn. 98 (2016) 200–207.  Y. Zhou, D. Xu, L. Zhang, Y. Ma, X. Ma, J. Gao, Y. Wang, Separation of thioglycolic acid from its aqueous solution by ionic liquids: ionic liquids selection by the COSMO-SAC model and liquid-liquid phase equilibrium, J. Chem. Thermodyn. 118 (2018) 263–273.  X. Xu, T. Zhao, Y. Wang, X. Geng, Y. Wang, Ternary liquid-liquid equilibrium of azeotropes (water +2-propanol) with ionic liquids ([Dmim][NTf2]) at different temperatures, J. Chem. Eng. Data 62 (2017) 1667–1672.  P. Wang, D. Xu, P. Yan, J. Gao, L. Zhang, Y. Wang, Separation of azeotrope (ethanol and ethyl methyl carbonate) by different imidazolium-based ionic liquids: Ionic liquids interaction analysis and phase equilibrium measurements, J. Mol. Liq. 261 (2018) 89–95.
 M.Z.M. Salleh, M.K. Hadj-Kali, I. Wazeer, E. Ali, M.A. Hashim, Extractive separation of benzene and cyclohexane using binary mixtures of ionic liquids, J. Mol. Liq. 285 (2019) 716–726.  S.P. Ventura, C.M. Neves, M.G. Freire, I.M. Marrucho, J. Oliveira, J.A. Coutinho, Evaluation of anion influence on the formation and extraction capacity of ionic-liquid-based aqueous biphasic systems, J. Phys. Chem. B 113 (2009) 9304–9310.  U. Doman´ska, A. Wis´niewska, Z. Da˛browski, M. Wie˛ckowski, Evaluation and correlation of separation heptane/ethanol with ionic liquids. Ternary liquidliquid phase equilibrium data, J. Mol. Liq. 255 (2018) 504–512.  M. Karpin´ska, M. Wlazło, U. Doman´ska, Separation of binary mixtures based on gamma infinity data using [EMIM][TCM] ionic liquid and modelling of thermodynamic functions, J. Mol. Liq. 225 (2017) 382–390.  F. Cai, G. Xiao, (Liquid+liquid) extraction of methanol from alkanes using dialkylphosphate-based ionic liquids as solvents, J. Chem. Thermodyn. 87 (2015) 110–116.  Y. Ma, X. Xu, G. Wen, D. Xu, P. Shi, Y. Wang, J. Gao, Separation of azeotropes hexane + ethanol/1-propanol by ionic liquid extraction: liquid-liquid phase equilibrium measurements and thermodynamic modeling, J. Chem. Eng. Data 62 (2017) 4296–4300.  A.B. Pereiro, J.M.M. Araújo, J.M.S.S. Esperança, I.M. Marrucho, L.P.N. Rebelo, Ionic liquids in separations of azeotropic systems – a review, J. Chem. Thermodyn. 46 (2012) 2–28.  F. Cai, G. Xiao, Liquid–liquid equilibria for ternary systems ethanol+heptane +phosphoric-based ionic liquids, Fluid Phase Equilib. 386 (2015) 155–161.  A. Cháfer, J. de la Torre, S. Loras, J.B. Montón, Study of liquid–liquid extraction of ethanol + water azeotropic mixtures using two imidazolium-based ionic liquids, J. Chem. Thermodyn. 118 (2018) 92–99.  N. Delgado-Mellado, A. Ovejero-Perez, P. Navarro, M. Larriba, M. Ayuso, J. García, F. Rodríguez, Imidazolium and pyridinium-based ionic liquids for the cyclohexane/cyclohexene separation by liquid-liquid extraction, J. Chem. Thermodyn. 131 (2019) 340–346.  X. Xu, W. Liu, M. Li, Y. Ri, Y. Wang, Ternary liquid-liquid equilibrium of azeotropes (ester + alcohol) with different ionic liquids at T = 298.15 K, J. Chem. Eng. Data 62 (2016) 532–538.  A.B. Pereiro, A. Rodríguez, Ternary (liquid+liquid) equilibria of the azeotrope (ethyl acetate+2-propanol) with different ionic liquids at T=298.15K, J. Chem. Thermodyn. 39 (2007) 1608–1613.  W. Liu, Z. Zhang, Y. Ri, X. Xu, Y. Wang, Liquid–liquid equilibria for ternary mixtures of water + 2-propanol + 1-alkyl-3-methylimidazolium bis (trifluoromethylsulfonyl)imide ionic liquids at 298.15 K, Fluid Phase Equilib. 412 (2016) 205–210.  X. Meng, X. Liu, J. Gao, D. Xu, L. Zhang, Y. Wang, Liquid-liquid equilibrium of isobutyl acetate + isobutyl alcohol + imidazolium-based ionic liquids at 298.15 and 308.15 K, J. Chem. Eng. Data. 64 (2019) 778–783.  H. Renon, J.M. Prausnit, Local compositions in thermodynamic excess functions for liquid mixtures, AICHE J. 14 (1968) 135–144.  J. Li, H. Zhu, C. Peng, H. Liu, Influence of binary ionic liquid mixtures of [BMIM] [Cl] and [BMIM][BF4] on isobaric vapor-liquid equilibrium of acetonitrile + water at atmospheric pressure, J. Mol. Liq. 284 (2019) 675–681.  P.K. Naik, S. Paul, T. Banerjee, Liquid Liquid Equilibria measurements for the extraction of poly aromatic nitrogen hydrocarbons with a low cost Deep Eutectic Solvent: experimental and theoretical insights, J. Mol. Liq. 243 (2017) 542–552.  X. Liu, D. Xu, B. Diao, L. Zhang, J. Gao, D. Liu, Y. Wang, Choline chloride based deep eutectic solvents selection and liquid-liquid equilibrium for separation of dimethyl carbonate and ethanol, J. Mol. Liq. 275 (2019) 347–353.  RobertEwald Treybal, Liquid extraction, 2nd ed., McGraw-Hill, 1963.  L. Zhang, D. Xu, J. Gao, M. Zhang, Z. Xia, Y. Ma, S. Zhou, Separation of the mixture pyridine + methylbenzene via several acidic ionic liquids: phase equilibrium measurement and correlation, Fluid Phase Equilib. 440 (2017) 103–110.  P. Yan, D. Xu, P. Wang, J. Gao, L. Zhang, Y. Wang, Liquid-liquid equilibrium measurement and thermodynamics modeling for the systems water + thioglycolic acid + isopropyl ether/methyl tert-butyl ether at 298.15 and 308.15 K, Fluid Phase Equilib. 476 (2018) 126–130.  U. Domanska, K. Walczak, Ternary liquid-liquid equilibria for mixtures of ionic liquid + thiophene or benzothiophene + heptane at T = 308.15 K, J. Solution Chem. 44 (2015) 382–394. _ A. Pobudkowska, Separation of hexane/  U. Doman´ska, Z. Zołek-Tryznowska, ethanol mixtures. LLE of ternary systems (ionic liquid or hyperbranched polymer + ethanol + hexane) at T= 298.15 K, J. Chem. Eng. Dat. 54 (2009) 972– 976.  E.J. González, N. Calvar, I. Domínguez, Á. Domínguez, Extraction of toluene from aliphatic compounds using an ionic liquid as solvent: influence of the alkane on the (liquid+liquid) equilibrium, J. Chem. Thermodyn. 43 (2011) 562– 568.  Q. Zeng, B. Hu, H. Cheng, L. Chen, J. Huang, Z. Qi, Liquid-liquid equilibrium for the system of ionic liquid [BMIm][HSO 4] catalysed isobutyl isobutyrate formation, J. Chem. Thermodyn. 122 (2018) 162–169.  X. Geng, X. Li, P. Cui, J. Yang, Z. Zhu, Y. Wang, D. Xu, Ternary liquid-liquid equilibrium of methanol + isopropyl acetate/methyl methacrylate + 1methylmidazole hydrogen sulfate at different temperatures and 1 atm, J. Mol. Liq. 283 (2019) 515–521.  G. Wen, W. Bai, F. Zheng, J.A. Reyes-Labarta, Y. Ma, Y. Wang, J. Gao, Ternary liquid–liquid equilibrium of an azeotropic mixture (hexane + methanol) with
X. Meng et al. / J. Chem. Thermodynamics 141 (2020) 105932
different imidazolium-based ionic liquids at T= 298.15K and 101.325kPa, Fluid Phase Equilib. 461 (2018) 51–56. R. Verma, T. Banerjee, Liquid-liquid extraction of lower alcohols using menthol-based hydrophobic deep eutectic solvent: experiments and COSMO-SAC predictions, Ind. Eng. Chem. Res. 57 (2018) 3371–3381. J. Li, X. Yang, K. Chen, Y. Zheng, C. Peng, H. Liu, Sifting ionic liquids as additives for separation of acetonitrile and water azeotropic mixture using the COSMORS method, Ind. Eng. Chem. Res. 51 (2012) 9376–9385. S.F. Boys, F. Bernardi, The calculation of small molecular interactions by the differences of separate total energies. Some procedures with reduced errors, Mol. Phys. 19 (2006) 553–566. F. Cai, J.J. Ibrahim, L. Gao, R. Wei, G. Xiao, A study on the liquid–liquid equilibrium of 1-alkyl-3-methylimidazolium dialkylphosphate with methanol and dimethyl carbonate, Fluid Phase Equilib. 382 (2014) 254–259. A. Haghtalab, A. Paraj, Computation of liquid–liquid equilibrium of organicionic liquid systems using NRTL, UNIQUAC and NRTL-NRF models, J. Mol. Liq. 171 (2012) 43–49. A. Samarov, N. Shner, E. Mozheeva, A. Toikka, Liquid-liquid equilibrium of alcohol–ester systems with deep eutectic solvent on the base of choline chloride, J. Chem. Thermodyn. 131 (2019) 369–374.
 A. Ghanadzadeh Gilani, S. Ahmadifar, T. Taki, Experimental and modeling study of liquid phase equilibria for (water + phosphoric acid + sec-alcohols) systems, J. Chem. Thermodyn. 135 (2019) 305–315.  G. Wen, X. Geng, W. Bai, Y. Wang, J. Gao, Ternary liquid-liquid equilibria for systems containing (dimethyl carbonate or methyl acetate + methanol + 1methylmidazole hydrogen sulfate) at 298.15 K and 318.15 K, J. Chem. Thermodyn. 121 (2018) 49–54.  G.W. Meindersma, A.J.G. Podt, A.B. de Haan, Ternary liquid–liquid equilibria for mixtures of toluene+n-heptane+an ionic liquid, Fluid Phase Equilib. 247 (2006) 158–168.  A.B. Pereiro, A. Rodríguez, Ternary liquidliquid equilibria ethanol + 2butanone + 1-butyl-3-methylimidazolium hexafluorophosphate, 2-propanol + 2-butanone + 1-butyl-3-methylimidazolium hexafluorophosphate, and 2butanone + 2-propanol + 1,3-dimethylimidazolium methyl sulfate at 298.15 K, J. Chem. Eng. Data 52 (2007) 2138–2142.