Article pubs.acs.org/jced
Ternary Liquid−Liquid Equilibrium of Azeotropes (Ester + Alcohol) with Different Ionic Liquids at T = 298.15 K Xicai Xu,† Wei Liu,† Min Li,† Yongsaeng Ri,†,‡ and Yinglong Wang*,† †
College of Chemical Engineering, Qingdao University of Science and Technology, 266042 Qingdao, China Faculty of Chemistry, Kim Il Sung University, Pyongyang 999093, DPR Korea
‡
ABSTRACT: The liquid−liquid equilibria (LLE) for ternary systems of npropyl acetate (PAC) + 1-propanol (NPA) + 1-butyl-3-methylimidazolium hexafluorophosphate ([Bmim][PF6]) or 1-hexyl-3-methylimidazolium hexafluorophosphate ([Hmim][PF6]) and n-butyl acetate (NBAC) + n-butanol (NBA) + [Bmim][PF6] or [Hmim][PF6] were measured at 298.15 K and 101.325 kPa. All the studied systems containing ionic liquids (ILs) show Treybal type I behavior of the LLE. The solute distribution coefficient (β) and the selectivity (S) were used to investigate the effect of the number of carbon atoms of cations, esters, and alcohols of ionic liquids on the liquid−liquid phase behavior for ester-alcohol-ILs. The measured data were correlated using both the NRTL model and the UNIQUAC model. Results indicate that all these systems can be correlated with reasonable accuracy by using both the NRTL model and the UNIQUAC model.
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INTRODUCTION Organic esters such as PAC or NBAC are important products and intermediate products in the chemical and pharmaceutical industries. PAC and NBAC are conventionally obtained from the direct esterification of NPA with acetic acid (HAc) or NBA with HAc, respectively. But, esterification is commonly an equilibrium-limited reaction, because of the reaction systems’ thermodynamics limited the conversion. Thus, mixtures of reactants (alcohol, acetic acid) and product (ester) are obtained during the esterification. Ordinary distillation cannot separate these mixtures effectively because of the formation of azeotropic mixtures. The negative environmental and health effects of volatile organic compound (VOCs) emissions have led to a huge surge of interest in research on substitutes of volatile organic solvents. Because of the particular physical and chemical properties, such as extremely low vapor pressure, chemical stability, heat insensitivity, incombustibility, and designability, in many chemical processes, ionic liquids (ILs) have recently obtained attention as possible environmentally friendly alternative solvents.1 Liquid−liquid extraction can be used for separating azeotropes for many reasons, such as high separating efficiency, energy savings, low carbon content, and applicability to a variety of separation systems. Because of their particular physical and chemical properties, ILs are suitable as extracting agents. For industrial application, their physical and chemical properties and the phase behavior of the relevant systems should be studied. The recently published literature shows that a large number of researchers have investigated liquid−liquid equilibria (LLE) containing ILs.2−21 Because there are a great amount of possible connections of cations and anions (estimated to be approximately 1018), both © XXXX American Chemical Society
the anion and the number of carbon atoms in the cation for an IL influence its physical characteristics, such as viscosity, polarity, and extracting power, and many researchers have studied how the phase behaviors change with the alkyl chain length of the cation.22−27 Hu et al.23 studied systems of an imidazolium-based IL with a [BF4] anion + ethanol + ethyl acetate, and the influence of the substituent group on the imidazolium ring was discussed. Naydenov et al.24,25 investigated systems for alcohol/acetic acid + ester + acidic ILs and discussed the impact of the number of carbon atoms in cation for the ILs, alcohol, and ester on the phase equilibria There are many researchers that have studied the phase behavior for alcohol + ester + IL systems, and some scholars used [PF6]− as an anion.26−28 Pereiro et al.28 chose different ILs ([Mmim][[MeSO4], [Bmim][PF6], and [Hmim][PF6]) to separate the azeotrope, such as ethyl acetate + 2-propanol. The experimental data demonstrate that the number of carbon atoms in the cation for ILs has a negative effect on the extractive capability of [Cnmim][PF6]. Cai et al.26,27 measured ternary systems of methyl acetate + methanol + [Emim][Ac] and 1butanol + butyl acetate + [Omim][PF6]. In this work, systems of PAC + 1-propanol + [Bmim][PF6], PAC + 1-propanol + [Hmim][PF6], NBAC + n-butanol + [Bmim] [PF6], and NBAC + n-butanol + [Hmim][PF6] were studied, focusing on the effect of the length of the n-alkyl chain in the IL cation, alcohol, and ester. No LLE data for alcohol-ester-[Bmim][PF6]/[Hmim][PF6] systems have been published. The distribution coefficient and selectivity were used to calculate the usability of ILs as Received: September 18, 2016 Accepted: December 16, 2016
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DOI: 10.1021/acs.jced.6b00811 J. Chem. Eng. Data XXXX, XXX, XXX−XXX
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systems of alcohol + ester + IL were as follows: helium was used (>99.999% purity) as the carrier gas, the temperature of the injector was 503.15 K, the column oven was maintained at 458.15 K for 3 min and subsequently submitted to the heating program from 458.15 to 503.15 K at a rate of 15 K/min and maintained at 503.15 K for 3 min, and the detector was at 523.15 K. The vacuum drying oven of DZF-6020 from Shanghai Boxun China was used to determine the composition of IL in the sample. By vaporizing the samples using a vacuum drying oven, the liquid samples’ mass difference before and after the vaporization at 308.2 K was calculated to determine the IL composition, as mentioned in our previous work.16 All the data were measured repeatedly at least three times.
extraction agents. The LLE data for all of the systems in our study were correlated with the UNIQUAC29 and NRTL30 models. The values of the room-mean-square deviation, known as rmsd, between the experimental and calculated data were also calculated.
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EXPERIMENTAL METHODS Chemicals. The chemical purities of 1-propanol, ethanol, nbutanol, PAC, and NBAC (purchased from Tianjin Kermel Chemical Reagent Co., Ltd. with a stated purity of >0.990 mass fraction) were detected by gas chromatography. The ILs [Bmim][PF6] and [Hmim][PF6] were supplied by the Lanzhou Institute of Chemical Physics, Chinese Academy of Sciences, with a stated purity >0.990 mass fraction. A list of the chemicals used in this study is shown in Table 1, including the source and purity information. All chemicals can be directly used, and no further purification is carried out.
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RESULTS AND DISCUSSION Experimental results. In this work, x presents the mole fraction of all compositions. All the experimental results of the ternary systems 1-propanol + PAC + [Bmim][PF6] or [Hmim][PF6] and n-butanol + NBAC + [Bmim][PF6] or [Hmim][PF6] at 298.15 K and 101.325 kPa are shown in Table 2.
Table 1. List of Chemicals Chemical
CAS number
Purity (mass fraction)
Ethanol
64-17-5
0.995a
1-propanol
71-23-8
0.995a
n-propyl acetate
109-60-4
0.995a
n-butanol
71-36-3
0.995a
n-butyl acetate
123-86-4
0.995a
1-butyl-3methylimidazolium hexafluorophosphate 1-hexyl-3methylimidazolium hexafluorophosphate
174501-64-5
0.990a
304680-35-1
0.990a
a
Table 2. LLE Data, Solute Distribution, β, and Selectivity, S, for Ternary Systems of Alcohol (1) + Ester (2) + ILs (3) at T = 298.15 K and p = 0.1 MPaa
Manufacturer Tianjin Kermel Chemical Reagent Co., Ltd. Tianjin Kermel Chemical Reagent Co., Ltd. Tianjin Kermel Chemical Reagent Co., Ltd. Tianjin Kermel Chemical Reagent Co., Ltd. Tianjin Kermel Chemical Reagent Co., Ltd. Lanzhou Institute of Chemical Physics, Chinese Academy of Sciences. Lanzhou Institute of Chemical Physics, Chinese Academy of Sciences.
Upper phase x1 0.999 0.887 0.827 0.768 0.696 0.627 0.512
Analysis by supplier.
0.995 0.966 0.942 0.922 0.889 0.866 0.833
Apparatus and procedure. LLE data were achieved through the configuration of mixtures with different compositions in the scope of two-phase. These mixtures were put into an equilibrium cell designed by ourselves and stirred vigorously with a mechanical stirrer. The temperature was controlled with an HX-105 low-temperature thermostat that was purchased from the Changliu Instrument Factory of Beijing in China. The standard uncertainty of temperature was 0.05 K, controlled with a thermostat. The sample mixtures were stirred rigorously for 3 h in the equilibrium cell. Then, these mixtures settled for approximately 15 h to reach equilibrium phases, which can ensure a complete separation. In pre-experimental testing, the experimental time was determined, and the cloud method31 was used to ensure that the LLE data can cover the scope of the twophase region as much as possible. The composition of each phase is determined by analyzing samples derived from the lower layers and the upper layers. The procedure and equipment to measure and determine the LLE data were given in a previous study.13 The relative compositions of the volatile compounds were determined with a gas chromatograph equipped (GC-2014C) with a thermal conductivity detector (TCD) using an internal standard method where ethanol is the internal standard substance. A packed column of GDX-104 (4 mm × 2 m) is connected to a precolumn, which can prevent the nonvolatile IL from entering the column. The detection conditions for the
1.000 0.818 0.747 0.672 0.603 0.550 0.492 0.448 0.998 0.906 0.881 0.829 0.775 0.727 0.663
x2
Lower phase x1
x2
β
1-propanol (1) + PAC (2) + [Bmim] [PF6] (3) 0.000 0.285 0.000 0.111 0.291 0.120 1.078 0.170 0.319 0.180 1.062 0.225 0.333 0.233 1.037 0.287 0.351 0.288 1.004 0.342 0.359 0.357 1.042 0.406 0.412 0.414 1.019 1-propanol (1) + PAC (2) + [Hmim] [PF6] (3) 0.000 0.415 0.000 0.029 0.425 0.044 1.537 0.052 0.455 0.075 1.425 0.071 0.492 0.101 1.420 0.098 0.528 0.129 1.318 0.112 0.542 0.143 1.275 0.132 0.572 0.160 1.212 n-butanol (1) + NBAC (2) + [Bmim] [PF6] (3) 0.000 0.155 0.000 0.176 0.161 0.102 0.580 0.246 0.17 0.144 0.469 0.319 0.173 0.191 0.599 0.386 0.172 0.230 0.596 0.439 0.180 0.264 0.601 0.495 0.178 0.307 0.619 0.539 0.177 0.338 0.627 n-butanol (1) + NBAC (2) + [Hmim] [PF6] (3) 0.000 0.250 0.000 0.087 0.306 0.093 1.075 0.112 0.340 0.134 1.203 0.160 0.360 0.187 1.165 0.209 0.389 0.217 1.038 0.251 0.418 0.262 1.042 0.293 0.444 0.299 1.022
S
3.289 2.754 2.393 1.993 1.824 1.266
3.491 2.948 2.660 2.218 2.039 1.764
2.948 3.143 2.328 2.097 1.837 1.708 1.585
3.180 3.116 2.682 2.070 1.811 1.526
a Standard uncertainties u are u(xi) = 0.006u(T) = 0.05 K and u(p) = 0.0015 MPa.
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DOI: 10.1021/acs.jced.6b00811 J. Chem. Eng. Data XXXX, XXX, XXX−XXX
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The experimental results for the four LLE systems (alcohol + ester + IL) are graphically presented in Figures 1−4. The phase
Figure 3. LLE phase diagram for the systems of n-butanol + NBAC + [Bmim][PF6] at T = 298.15 K. (■) experimental value; (●) calculated value by the NRTL model; (▲) calculated value by the UNIQUAC model; (○) from ref 39.
Figure 1. LLE phase diagram for the systems of 1-propanol + PAC + [Bmim][PF6] at T = 278.15 K. (■) experimental value; (●) calculated value by the NRTL model; (▲, calculated value by the UNIQUAC model; (○) from ref 39.
Figure 4. LLE phase diagram for the systems of n-butanol + NBAC + [Hmim][PF6] at T = 298.15 K. (■) experimental value; (●) calculated value by the NRTL model; (▲) calculated value by the UNIQUAC model; (○) from ref 39.
Figure 2. LLE phase diagram for the systems of 1-propanol + PAC + [Hmim][PF6] at T = 298.15 K. (■) experimental value; (●) calculated value by the NRTL model; (▲) calculated value by the UNIQUAC model; (○) from ref 39.
behavior of a 1-propanol and PAC mixture when [Bmim][PF6] and [Hmim][PF6] were used as solvents. As shown in Figure 1, the tie-lines for the system of 1-propanol + PAC + [BMIM][PF6] are almost horizontal, and the values of the distribution coefficient are close to unity. As shown in Figure 2, the slope of the tie-lines is large enough for the extraction, and the values of the distribution coefficient are greater than unity. The values of selectivity slightly increase with the increasing number of carbon atoms of the cation of the IL. On the other hand, the LLE phase behaviors of 1-butanol and NBAC mixtures when using both ILs mentioned above as solvents can be observed in Figures 3 and 4, respectively. In Figure 3, the slope of the tie-lines shows that the ester has more affinity to the alcohol-rich phase than to the ILrich phase, and the values of the distribution coefficient are smaller than unity. In Figure 4, the tie-lines are almost horizontal, and the values of the distribution coefficient are close to unity. This shows that the number of carbon atoms of the IL cation has
behaviors of all the systems are Treybal type I, which was shown in Figures 1−4. The systems for this type have the characteristics of two miscible binary subsystems and one partial miscible binary subsystem. The partially miscible binary is the alcohol and IL. For the alcohol + ester + IL systems, the solubility of ILs in the organic-rich phase increases as the mount of ester added increases. The results from the same alcohol + ester systems with different ILs indicate that the increase in the number of carbon atoms of the cation enhances the capability of the ILs to extract the ester, and from the same IL with different alcohol + ester systems, we can see that as the number of carbon atoms on the alcohol and ester increase, the immiscibility region of the ternary phase diagram enlarges, and the extraction capability of the ILs reduces slightly. We observed the same tendency as shown in a previous reference.22 Figures 1 and 2 show the LLE phase C
DOI: 10.1021/acs.jced.6b00811 J. Chem. Eng. Data XXXX, XXX, XXX−XXX
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an enormous influence on the systems of n-butanol + NBAC + IL. For the same IL, as the alkyl chain lengths of the alcohol and ester increase, the extraction capability of the IL decreases slightly. These results are in consonance with the values of the distribution coefficient shown in Figure 5, and the values of the
Figure 7. Solubility (mole fraction) of alcohol in [Cnmim][PF6] at 298.15 K: (□) from Pereiro et al.39 for [Bmim][PF6] + 1-propanol; (■) from this work for [Bmim][PF6] + 1-propanol; (○) from Pereiro et al.39 for [Bmim][PF6] + n-butanol; (⊙) from Huo40 for [Bmim][PF6] + nbutanol; (●) from this work for [Bmim][PF6] + n-butanol; (▽) from Pereiro et al.39 for [Hmim][PF6] + 1-propanol; (▼) from this work for [Hmim][PF6] + 1-propanol; (◇) from Pereiro et al.39 for [Hmim][PF6] + n-butanol; (◆) from Pereiro et al.39 for [Hmim][PF6] + nbutanol.
Figure 5. Distribution coefficient (β) against xI2 for ternary systems for the systems of alcohol + ester + IL: (■) (PAC + 1-propanol + [Bmim][PF6]); (●) (NBAC + n-butanol + [Bmim][PF6]); (▲) (PAC + 1-propanol + [Hmim][PF6]); (▼) (NBAC + n-butanol + [Hmim][PF6]).
this work. The distribution coefficients of the alcohol are given in eq 1 β=
x 2II x 2I
(1)
where xII2 is the component fraction of ester in mole in the IL-rich phase, and xI2 is the component fraction of ester in mole in the organic-rich phase. The selectivities of alcohols are given in eq 2
S=
(x 2II/x1II) (x 2I/x1I)
(2)
xI1
where is the component fraction of ester in mole in the organic-rich phase, and xII1 is the component fraction of alcohol in mole in the IL-rich phase. The values of β and S for the four ternary systems are graphically shown in Figures 5 and 6. For the systems of the same alcohol + ester with different ILs, the values of the selectivity and distribution coefficient slightly increase with the increase in the number of carbon atoms of the IL cation. The tendency of this work is in accordance with that of a previous study.22 The β values decrease with the increasing ester mole fraction, and all of the values for the selectivity S are larger than 1, which indicates that the extraction of ester from alcohol by ILs indicated in this work is feasible. LLE correlation. During the regression of the parameters, the following equation was used to determine the activity coefficient and mole fraction:
Figure 6. Selectivity (S) against xI2 for ternary systems for the systems of alcohol + ester + IL: (■) (PAC + 1-propanol + [Bmim][PF6]); (●) (NBAC + n-butanol + [Bmim][PF6]); (▲) (PAC + 1-propanol + [Hmim][PF6]); (▼) (NBAC + n-butanol + [Hmim][PF6]).
selectivity are all greater than unity, as shown in Figure 5. In Figure 7, the solubilities in this work and the literature39,40 were compared. The method we used is different from those of the literature. The deviations in the results as can be seen from Figure 7 are acceptable. The distribution coefficient (β) was used to estimate the extractive abilities of the ILs studied in this work as solvents for the purity of the ester from alcohol, and the selectivity (S) was also used to evaluate the extractive abilities of the ILs studied in
γi IxiI = γi IIxiII
(3)
where xIi is the component fraction in mole of component i in the upper phase, xIIi is the component fraction in mole of component i in the lower phase, γIi is the activity coefficients of component i in the organic-rich phase, and γIIi is the activity coefficients of component i in IL-rich phase, respectively. The key to obtain the D
DOI: 10.1021/acs.jced.6b00811 J. Chem. Eng. Data XXXX, XXX, XXX−XXX
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To obtain accurate results for the LLE correlation, the objective function was used to determine the binary interaction parameters of both the NRTL model and the UNIQUAC model.
calculated data which were correlated by models is to determine the activity coefficients. The appropriate thermodynamic model is critical for the design and optimization of chemical processes. The NRTL and UNIQUAC models have been used by many scholars to correlate the systems containing IL.32−38 The MATLAB was used to regress the parameters of both the NRTL and UNIQUAC models via the nonlinear least-squares method in this work. The NRTL activity coefficient model and the required interaction parameters used in this work are given in eq 3. ln γi =
τij =
∑j τjiGjixj ∑k Gkixk
Δgij RT
+
∑ j
M
OF =
(4)
where xi denotes the component fraction in mole of component i, γi is the activity coefficient of component i, and T is the experimental temperature. Δgij presents the binary interaction parameter of components i and j, which were regressed in this work. αij is a nonrandomness factor, which has been fixed to 0.3, and αij is equal to αji. The UNIQUAC activity coefficient model and the required interaction parameters used in this work are given by eq 4.
Table 4. NRTL and UNIQUAC Binary Interaction Parameters for Ternary Systems Ester (1) + Alcohol (2) + ILs (3) at T = 298.15 K and p = 0.1 MPa NRTL parameters
ln γi = ln
θi =
qixi ∑j qixj
θi′ =
⎛ Δuij ⎞ τij = exp⎜ − ⎟ ⎝ RT ⎠
qi′xi
∑ j
Φi =
∑j q′j xj
i−j
θj′τij ⎞ ⎟ ∑k θkτkj ⎟⎠
1−2 1−3 2−3
rx i i ∑j rjxj
1−2 1−3 2−3
⎛ Δuji ⎞ τji = exp⎜ − ⎟ ⎝ RT ⎠
1−2 1−3 2−3
(5)
where z is the number of close-interacting molecules around a central molecule, which is set to 10, and Φi is the volume fraction of component i, and θi represents the area fraction of component i,. Δuij is the binary interaction parameter of components i and j in the UNIQUAC model, which were regressed in this work. The molecular volume structure parameters r and the molecular surface area parameters q were from a previous reference.39 Parameters r, q, and q′ of the IL for the UNIQUAC model are listed in Table 3. For most substances, q is equal to q′, except for water and some small alcohols.
1−2 1−3 2−3 i−j 1−2 1−3 2−3
Table 3. UNIQUAC Structural Parameters of Pure Componentsa
a
Component
ri
qi
[Bmim] [PF6] [Hmim] [PF6] 1-propanol n-butanol PAC NBAC Ethanol
8.4606 9.6811 2.8210 3.5240 4.2550 4.9390 2.5755
6.8080 7.8450 2.4480 2.9080 3.5440 4.0300 2.5880
(6)
where M is the number of tie-lines, xexp and xcalc indicate the experimental and calculated mole fractions, respectively, i presents the component, j is the phase, and k indicates the tieline, respectively. As observed from Figures 1−4, the experimental and calculated LLE data from the NRTL and UNIQUAC models agree relatively well. The regressed parameters are presented in Table 4. The root-mean-square deviation, known as rmsd, which is commonly treated as a criterion in evaluating the correlation accuracy, was used to examine the consistency between the experimental and calculated data and is defined as follows:
⎛ ∑ τG x ⎞ ⎜⎜τij − v vj vj v ⎟⎟ ∑k Gkjxk ⎠ ∑k Gkjxk ⎝
Φi θ z + qi ln i + li Φi xi 2 ⎛ Φ − i ∑ xjl j + qi × ⎜⎜1 − ln(∑ θj′τji) − xi j j ⎝
3
k=1 j=1 i=1
Gjixj
Gij = exp( −αijτij)
2
∑ ∑ ∑ (xijkexp − xijkcalc)2
qi
1−2 1−3 2−3
′
6.8080 7.8450 2.4480 2.9080 3.5440 4.0300 0.9200
1−2 1−3 2−3 1−2 1−3 2−3
From reference R. S. Santiago et al.39 E
Δgij (kJ·mol−1)
Δgji (kJ·mol−1)
rmsd
1-propanol (1) + PAC (2) + [Bmim] [PF6] (3) −1.3260 −4.0212 0.0161 14.4883 2.3015 9.6387 −7.1896 1-propanol (1) + PAC (2) + [Hmim] [PF6] (3) 2.6516 −6.0751 0.0091 12.8091 0.9581 10.4574 −8.0863 NBAC (1) + n-butanol (2) + [Bmim] [PF6] (3) 31.1941 −0.7369 0.0113 17.4340 7.2187 8.6654 −0.6413 n-butanol (1) + NBAC (2) + [Hmim] [PF6] (3) 3.8224 −3.3633 0.0061 12.5092 2.0546 7.3262 −3.0487 UNIQUAC parameters Δuij (kJ·mol−1)
Δuji (kJ·mol−1)
α 0.3
0.3
0.3
0.3
rmsd
1-propanol (1) + PAC (2) + [Bmim] [PF6] (3) 0.9531 −1.0196 0.0092 2.7998 0.10354 1.8597 −1.2637 1-propanol (1) + PAC (2) + [Hmim] [PF6] (3) 1.6650 −1.7350 0.0094 1.7633 0.3397 −0.1081 −0.2451 NBAC (1) + n-butanol (2) + [Bmim] [PF6] (3) 0.9001 −0.4399 0.0122 1.8622 0.6300 3.0684 −1.0900 NBAC (1) + n-butanol (2)+ [Hmim] [PF6] (3) 1.6133 −0.85753 0.0108 1.78493 0.28043 1.04843 −0.29303 DOI: 10.1021/acs.jced.6b00811 J. Chem. Eng. Data XXXX, XXX, XXX−XXX
Journal of Chemical & Engineering Data ⎛ M 2 3 (x exp − x calc)2 ⎞1/2 ijk ijk ⎟ rmsd = ⎜⎜∑ ∑ ∑ ⎟ 6 M ⎝k=1 j=1 i=1 ⎠
Article
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where x is the component fraction of the studied substances measured or calculated in mole, the subscripts i presents the component, l is the phase, and M denotes the tie-line, respectively. The experimental data fit well for both models. The calculated tie-line data are also shown in Figures 1−4. As for the systems of 1-propanol + PAC + [HMIM][PF6] and nbutanol + NBAC + [BMIM][PF6], the values of rmsd for the two models are close. As for the system of 1-propanol + PAC + [BMIM][PF6], the value of rmsd for the NRTL model is bigger than the value for the UNIQUAC model. As for the system of nbutanol + NBAC + [HMIM][PF6], the value of rmsd for the NRTL model is smaller than the value for the UNIQUAC model.
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CONCLUSION In this work, we focused on ternary systems including an alcohol (NPA, NBA), an ester (PAC, NBAC), and an ILs ([Bmim][PF6], [Hmim][PF6]) at 298.15 K and 101.325 kPa. New LLE data for alcohol + ester + IL systems were obtained. The capability of the IL as a liquid−liquid extraction solvent was assessed using the distribution coefficient (β) and selectivity (S). The values of S are greater than 1, which indicates that the extraction of an ester from an alcohol ester mixture by ILs examined in this work is feasible. The results indicate that the increase in the number of carbon atoms of the cation enhances the capability of the ILs to extract the ester, and as the alkyl chain lengths of the alcohol and ester increase, the immiscibility region of the ternary phase diagram grows. The LLE data for the systems studied were correlated by both the NRTL model and the UNIQUAC model, and the calculated data were obtained by computing with the binary interaction parameters determined from the experimental data regression. The comparative results of the rmsd between the calculated data and the experimental data show that the two models properly correlate the data for the systems studied in this work. In some cases (Figures 1 and 4), the calculated tie-lines have a change of slope with respect to the experimental tie-line, which indicates that the two models cannot perfectly reflect the tendency of the experimental data.
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AUTHOR INFORMATION
Corresponding Author
*E-mail:
[email protected]. ORCID
Yinglong Wang: 0000-0002-3043-0891 Funding
Financial support from the National Natural Science Foundation of China (Project 21306093) is gratefully acknowledged. Notes
The authors declare no competing financial interest.
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REFERENCES
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DOI: 10.1021/acs.jced.6b00811 J. Chem. Eng. Data XXXX, XXX, XXX−XXX
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