Phase Equilibrium for Quaternary Systems of Water + Methanol +

Jun 18, 2015 - ... water + diethyl carbonate + methylbenzene at 298.15 K and atmospheric pressure. The experimental tie-line data were correlated usin...
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Phase Equilibrium for Quaternary Systems of Water + Methanol + Diethyl Carbonate + Methylbenzene or Heptane or Cyclohexane Yao Chen,* Cui Wang, Jitai Guo, Xiaoming Zhou, and Caiyu Wen Department of Chemistry, Jinan University, Guangzhou 510632, China ABSTRACT: Tie-line phase compositions were experimentally determined for three quaternary systems of water + methanol + diethyl carbonate + methylbenzene or heptane or cyclohexane and one related ternary system of water + diethyl carbonate + methylbenzene at 298.15 K and atmospheric pressure. The experimental tie-line data were correlated using the modified and extended UNIQUAC activity coefficient models. Furthermore, the effect of hydroxyl group on the solubility of alcohols in the two phases was compared.

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INTRODUCTION Methyl tert-butyl ether (MTBE) has been used as a gasoline additive for increasing the octane number and decreasing the emission of carbon monoxide over the past decade. However, it has known environmental problems, such as polluting the groundwater and not being biodegradable.1 Due to the disadvantages of MTBE, researchers have studied alternatives such as the dialkyl carbonates.2−4 Diethyl carbonate (DEC) has low solubility in water and has both low toxicity and relatively rapid biodegradability and hence has been recommended as a replacement for MTBE. The addition of oxygenated additives, such as pure DEC or mixtures with C4 alcohols in gasoline, not only enhances the octane rating of gasoline but also can improve the combustion process by reducing carbon monoxide and aromatic emissions. However, adding DEC into gasoline influences the solubility of the gasoline compositions. Liquid− liquid equilibria (LLE) data (including multicomponent) can help provide understanding of the solution behavior and provide a scientific basis for developing gasoline additives. In this study, methylbenzene, methanol, heptane, cyclohexane, and DEC were simulated as the formulations of the basic gasoline compositions. Considering the presence of water in the leakage of oil tanks in gasoline stations and in the process of transportation and storage, in this case water maybe considered as a component in gasoline. In this study, we report LLE data for one ternary system of water + DEC + methylbenzene and three quaternary systems of water + methanol + DEC + methylbenzene or heptane or cyclohexane at 298.15 K. The measured LLE results were correlated using the modified and extended UNIQUAC models. 5,6 The binary vapor−liquid equilibria (VLE) data7−12 and mutual solubility data,13−16 and the ternary LLE data13,17−20 are necessary for the quaternary correlation calculations. © 2015 American Chemical Society

EXPERIMENTAL SECTION Materials. DEC with a nominal purity of 0.990 mass fraction was purchased from Aladdin, whereas heptane and cyclohexane with a nominal purity of 0.997 and 0.995 mass fraction, respectively, were supplied by Fuyu. Methanol and methylbenzene were provided by Guangzhou Chemical Reagent Factory, with nominal purities of 0.995 and 0.990 mass fraction, respectively. These purities were checked by gas chromatography, and the chemicals were used without further purification. The electrical conductivity of bidistilled water used in this work was measured with a conductivity meter. The purities, suppliers, and analysis methods of the chemicals used in this study are reported in Table 1. Procedure and Results. The LLE apparatus17 and experimental procedure21 were previously described in detail. To determine the tie lines, the quaternary mixtures were prepared by mixing water and methanol with the premade mixtures of {x3′DEC + (1-x3′) methylbenzene} or {x3′DEC + (1 − x3′)heptane} or {x3′DEC + (1 − x3′)cyclohexane}. The mole fractions of DEC, x3′, are equal to 0.20, 0.40, 0.60, and 0.80. The mixtures in the cell were stirred in a water bath for 3 h, and the cells were placed at the same water bath for 3 h at atmospheric pressure. The temperature of the water bath was controlled at 298 K with a precision of 0.1 K. The time, 3 h for phase equilibrium and phase splitting, was obtained according to our previous experiments. The samples of the aqueous phase and organic phase were carefully withdrawn by using syringes. The analysis of water, methanol, DEC, methylbenzene, heptane, and cyclohexane was performed using a gas chromatograph (GC-14C) equipped with a thermal conductivity detector. Received: January 14, 2015 Accepted: June 1, 2015 Published: June 18, 2015 2062

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Table 1. Purities and Suppliers of Chemicals

a

chemical

purity

supplier

analysis method

DEC (AR)a cyclohexane (AR) methanol (AR) methylbenzene (AR) heptane (AR) water (bidistilled)

0.9942b 0.9960b 0.9944b 0.9972b 0.9954b 0.8910 μs·cm−1

Aladdin Reagent Co. (Shanghai, China) Fuyu Reagent Co. (Tianjin,China) Guangzhou Reagent Co. (Guangzhou,China) Guangzhou Reagent Co. (Guangzhou,China) Fuyu Reagent Co. (Tianjin,China) Jinan University (Guangzhou,China)

GC GC GC GC GC conductivity meter

AR represents analytical reagent. bThe purity is represented by mass fraction.

Table 3. Tie-Line Compositions of Quaternary Mixtures of Water (1) + Methanol (2) + Diethyl Carbonate (3) + Methylbenzene (4) for Mole Fractions x at T = 298.15 K and p = 0.1 MPaa xI1

xI2

xI3

xII1

xII2

xII3

{x1Water + x2Methanol + x3Diethyl Carbonate + (1 − x1 − x2 − x3) Methylbenzene}b

Figure 1. Phase equilibria of (water + methanol + DEC + methylbenzene or heptane or cyclohexane). x3′ denotes quaternary section planes.

Table 2. Tie-Line Compositions of Ternary Mixtures of Water (1) + Diethyl Carbonate (2) + Methylbenzene (3) for Mole Fractions x at T = 298.15 K and p = 0.1 MPaa xI1

xI2

xI3

xII1

xII2

xII3

< 0.0001 0.0038 0.0051 0.0095 0.0138 0.0164 0.0196 0.0474

< 0.0001 0.2317 0.3262 0.3635 0.4359 0.5345 0.5901 0.9526

1.0000 0.7645 0.6687 0.6270 0.5503 0.4491 0.3903 0.0000

1.0000 0.9978 0.9951 0.9933 0.9926 0.9922 0.9910 0.9906

< 0.0001 0.0022 0.0029 0.0048 0.0052 0.0054 0.0066 0.0066

< 0.0001 0.0000 0.0020 0.0019 0.0022 0.0024 0.0024 0.0028

a Standard uncertainties u are u (T) = 0.05 K, u (x) = 0.0005, and u (p) = 10 kPa. I, organic phase. II, aqueous phase.

The initial and final temperatures of the column were set at 433.15 K and 483.15 K, respectively. The temperature of the detector and injection port was set at 493.15 K. Hydrogen was the carrier gas with the column flow rate of 65 cm3·min−1. A Porapak QS packed column (3 mm × 2.5 m) was used to separate each component. Area normalization method was used for quantitative analysis in this work. The peak area of each component, measured with a chromatopac (MR98S), was calibrated by gravimetrically prepared mixtures. Each sample was analyzed at least three times to ensure that the repeatability of the measured mole fraction was better than 0.04 %. The uncertainty of the phase composition measurements in mole fraction is 0.05 %. Figure 1 displays a tetrahedral phase diagram for the quaternary LLE of water + methanol + DEC + methylbenzene, water + methanol + DEC + heptane, and water + methanol + DEC + cyclohexane systems. x3′ delegates quaternary section planes. Table 2 presents the measured experimental LLE data for the

0.0000 0.0000 0.0000 0.0000 0.0000 0.0000

0.0000 0.0074 0.0126 0.0185 0.0113 0.0293

0.0000 0.0000 0.0058 0.0090 0.0084 0.0101 0.0108 0.0129

0.0052 0.0108 0.0238 0.0259 0.0317 0.0390 0.0424 0.0618

0.0120 0.0000 0.0000 0.0000 0.0140 0.0168 0.0186 0.0205

0.0058 0.0121 0.0239 0.0312 0.0376 0.0487 0.0628 0.0774

0.0115 0.0133 0.0137 0.0184 0.0184 0.0245 0.0232 0.0266

0.0081 0.0153 0.0256 0.0409 0.0474 0.0622 0.0753 0.0839

x3′ = 0.20c 0.1614 0.9513 0.1601 0.9206 0.1609 0.8718 0.1661 0.8485 0.1644 0.8191 0.1553 0.7745 x3′ = 0.40c 0.2848 0.9493 0.2817 0.9141 0.2752 0.8752 0.2678 0.8362 0.2664 0.8147 0.2603 0.7754 0.2567 0.7308 0.2382 0.6981 x3′ = 0.60c 0.3601 0.9588 0.3613 0.9228 0.3525 0.8827 0.3487 0.8456 0.3414 0.8169 0.3355 0.7788 0.3195 0.7335 0.3044 0.6993 x3′ = 0.80c 0.4308 0.9540 0.4278 0.9180 0.4220 0.8836 0.4061 0.8430 0.4009 0.8114 0.3837 0.7756 0.3725 0.7336 0.3717 0.7285

0.0487 0.0794 0.1282 0.1515 0.1809 0.2255

0.0000 0.0000 0.0000 0.0000 0.0000 0.0000

0.0507 0.0859 0.1248 0.1638 0.1853 0.2246 0.2692 0.3019

0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000

0.0412 0.0772 0.1173 0.1544 0.1831 0.2212 0.2665 0.3007

0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000

0.0460 0.0820 0.1164 0.1570 0.1886 0.2196 0.2605 0.2664

0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000

a

Standard uncertainties u are u (T) = 0.05 K, u (x) = 0.0005, and u (p) = 10 kPa. bObtained by mixing pure water and methanol with the binary mixtures of {x3′diethyl carbonate + (1 − x3′) methylbenzene}. c Mole fraction of diethyl carbonate in the binary mixtures: I, organic phase; II, aqueous phase.

ternary system of water + DEC + methylbenzene at 298.15 K. Tables 3−5 summarize the experimental LLE data for the quaternary systems of water + methanol + DEC + methylbenzene, water + methanol + DEC + heptane, and water + methanol + DEC + cyclohexane at 298.15 K. 2063

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Table 4. Tie-Line Compositions of Quaternary Mixtures of Water (1) + Methanol (2) + Diethyl Carbonate (3) + Heptane (4) for Mole Fractions x at T = 298.15 K and p = 0.1 MPaa xI1

xI2

xI3

xII1

xII2

Table 5. Tie-Line Compositions of Quaternary Mixtures of Water (1) + Methanol (2) + Diethyl Carbonate (3) + Cyclohexane (4) for Mole Fractions x at T = 298.15 K and p = 0.1 MPaa

xII3

xI1

{x1Water + x2Methanol + x3Diethyl Carbonate + (1 − x1 − x2 − x3)Heptane}b 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000

0.0000 0.0000 0.0000 0.0000 0.0082 0.0052 0.0052

0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000

0.0000 0.0000 0.0073 0.0086 0.0119 0.0137 0.0124 0.0153

0.0000 0.0132 0.0165 0.0194 0.0204 0.0155 0.0237 0.0243

0.0059 0.0067 0.0073 0.0109 0.0128 0.0157 0.0197 0.0224

0.0000 0.0106 0.0100 0.0126 0.0160 0.0139

0.0076 0.0096 0.0115 0.0157 0.0291 0.0349

x3′ = 0.20c 0.1381 0.9529 0.1393 0.9116 0.1245 0.8370 0.1147 0.8052 0.0974 0.7405 0.1186 0.7638 0.0915 0.6873 x3′ = 0.40c 0.2253 0.9578 0.2387 0.9242 0.2292 0.8866 0.2306 0.8448 0.2115 0.7904 0.2003 0.7556 0.1860 0.7230 0.1643 0.6865 x3′ = 0.60c 0.3273 0.9495 0.3189 0.9075 0.3123 0.8600 0.3024 0.8217 0.2952 0.7926 0.2806 0.7506 0.2645 0.7310 0.2401 0.6870 x3′ = 0.80c 0.3937 0.9484 0.3872 0.9007 0.4081 0.8662 0.3731 0.8280 0.3204 0.7193 0.2990 0.6843

0.0471 0.0884 0.1630 0.1948 0.2595 0.233 0.3127

0.0000 0.0000 0.0000 0.0000 0.0000 0.0031 0.0000

0.0422 0.0758 0.1134 0.1552 0.2058 0.2398 0.2716 0.3070

0.0000 0.0000 0.0000 0.0000 0.0038 0.0046 0.0054 0.0065

0.0481 0.0905 0.1372 0.1748 0.2030 0.2439 0.2636 0.3056

0.0024 0.0020 0.0028 0.0036 0.0044 0.0055 0.0054 0.0074

0.0490 0.0968 0.1338 0.1720 0.2736 0.3070

0.0026 0.0024 0.0000 0.0000 0.0071 0.0087

i

i

xII3

0.0000 0.0000 0.0000 0.0000 0.0123 0.0000

0.0000 0.0000 0.0000 0.0000 0.0000 0.0000

0.0085 0.0147 0.0142 0.0147 0.0191 0.0201 0.0269 0.0086

0.0000 0.0067 0.0060 0.0070 0.0067 0.0057 0.0061 0.0042

0.0000 0.0113 0.0148 0.0151 0.0200 0.0189 0.0207 0.0217

0.0073 0.0089 0.0118 0.0138 0.0159 0.0165 0.0201 0.0229

0.0000 0.0092 0.0109 0.0108 0.0117 0.0096 0.0096 0.0124

0.0089 0.0098 0.0126 0.0147 0.0188 0.0217 0.0233 0.0267

x3′ = 0.20c 0.1541 0.9475 0.1550 0.9077 0.1493 0.8604 0.1438 0.8177 0.1405 0.7932 0.1382 0.7563 x3′ = 0.40c 0.2705 0.9446 0.2672 0.9038 0.2613 0.8577 0.2577 0.8197 0.2418 0.7947 0.2362 0.7540 0.2235 0.7159 0.2115 0.6964 x3′ = 0.60c 0.3668 0.9438 0.3504 0.9053 0.3435 0.8581 0.3356 0.8189 0.3297 0.7974 0.3156 0.7541 0.3028 0.7298 0.2801 0.6857 x3′ = 0.80c 0.3641 0.9456 0.3605 0.9118 0.3715 0.8576 0.3476 0.8177 0.3442 0.7948 0.3277 0.7568 0.3130 0.7219 0.3042 0.6903

0.0509 0.0908 0.1379 0.1790 0.2042 0.2406

0.0016 0.0014 0.0018 0.0033 0.0025 0.0031

0.0534 0.0946 0.1400 0.1775 0.2019 0.2418 0.2785 0.2976

0.0019 0.0015 0.0023 0.0027 0.0035 0.0042 0.0056 0.0060

0.0544 0.0927 0.1392 0.1778 0.1986 0.2408 0.2641 0.3063

0.0018 0.0020 0.0027 0.0033 0.0040 0.0051 0.0061 0.0079

0.0520 0.0859 0.1398 0.1790 0.2012 0.2380 0.2716 0.3022

0.0024 0.0022 0.0026 0.0033 0.0041 0.0052 0.0065 0.0076

τ1234 were used for accurate correlation of the ternary and quaternary LLE. Equations 1 and 2 were also employed to calculate the measured ternary and quaternary LLE. The ternary and quaternary parameters were obtained using a simplex method.23 The root-mean-square deviation (rmsd) is used as a measure of the precision of the models’ calculations. The rmsd value was calculated from the difference between the experimental and calculated mole fractions of tie-line data according to the following equation

(1)

∑ xiII = 1

xII2

Standard uncertainties u are u (T) = 0.05 K, u (x) = 0.0005, and u (p) = 10 kPa. bObtained by mixing pure water and methanol with the binary mixtures of {x3′diethyl carbonate + (1 − x3′)cyclohexane}. c Mole fraction of diethyl carbonate in the binary mixtures: I, organic phase; II, aqueous phase.

CALCULATION PROCEDURE The modified and extended UNIQUAC models were employed to fit the experimental data. For completely miscible binary mixtures, an optimum set of the energy parameters aij was evaluated from experimental VLE data using a computer program described by Prausnitz et al.22 For partially miscible binary mixtures, the energy parameters were obtained from mutual solubility data by solving the thermodynamic criteria and mass balance equations.

and

xII1

a

■

∑ xiI = 1

xI4

{x1Water + x2Methanol + x3Diethyl Carbonate + (1 − x1 − x2 − x3) Cyclohexane}b

a Standard uncertainties u are u (T) = 0.05 K, u (x) = 0.0005, and u (p) = 10 kPa. bObtained by mixing pure water and methanol with the binary mixtures of {x3′diethyl carbonate + (1 − x3′) heptane}. c Mole fraction of diethyl carbonate in the binary mixtures: I, organic phase; II, aqueous phase.

(xiγi)I = (xiγi)II

xI2

exp cal 2 rmsd = [∑ ∑ ∑ (xijk − xijk ) /6n]0.5

(2)

k

where I and II represent the equilibrium phases, x is the mole fraction in liquid phase, and γ is the activity coefficient given by the modified or extended UNIQUAC models. The ternary parameters τ231, τ312, and τ123 and quaternary parameters τ2341, τ1342, τ1243, and

i

j

(3)

Here i = 1 to 3 for ternary mixtures or i = 1 to 4 for quaternary mixtures, j = 1, 2 (phases), k = 1, 2, ..., n (tie lines), and x denotes the liquid phase mole fraction. 2064

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Table 6. Calculated Results of Binary Phase Equilibrium Data Reduction system (1 + 2) water + methanol methanol + methylbenzene DEC + heptane DEC + cyclohexane methanol + DEC DEC + methylbenzene methanol + cyclohexane methanol + heptane water + DEC water + heptane water + methylbenzene water + cyclohexane a

a12

a21

δ(P)

δ(T)

K

K

kPa

K

103δ(x)

103δ(y)

lit.

−160.39 −71.81 906.82 867.82 144.16 181.81 −55.36 −50.63 583.84 583.40 941.00 −414.56 1217.97 1059.03 1188.97 1012.00 1177.60 961.41 1884.2 2135.5 1713.30 1540.70 2429.90 1942.50

0.1 0.1 0.1 0.1 1.3 1.3 2.5 2.5 2.0 2.0 9.0 8.6 0.9 1.1 1.7 2.3

0.0 0.0 0.0 0.0 0.1 0.1 0.1 0.1 0.1 0.1 0.5 0.4 0.1 0.1 0.1 0.2

0.6 0.6 0.1 0.7 0.8 0.8 2.8 2.8 3.1 3.2 2.4 3.3 1.6 1.1 0.8 1.5

4.0 4.1 3.0 3.1 8.0 7.9 8.1 8.1 3.5 3.5 26.5 24.2 6.5 5.8 7.6 10.2

7

a

158.59 70.15b 19.30 93.98 31.27 69.12 214.20 233.46 −121.53 −183.98 −425.36 397.19 173.49 162.11 128.12 140.02 248.21 273.66 1022.10 1839.60 752.99 1053.90 1157.80 1315.60

8 9 9 10 11 12 12 13 14 15 16

Modified UNIQUAC model. bExtended UNIQUAC model.

Table 7. Calculated Results for Ternary Liquid−Liquid Equilibria at 298.15 K Na

τ231

water + methanol + DEC

8

water + DEC + heptane

13

water + DEC + cyclohexane

12

−1.4828 −0.8235c −0.0333 −0.0230 0. 1260 0.2722 −0.0048 −0.0453 −0.5529 −0.6123 −0.1763 −1.3601 0.1540 −1.3358

system (1 + 2 + 3)

water + DEC + methylbenzene

8

water + methanol + methylbenzene

11

water + methanol + cyclohexane

12

water + methanol + heptane

3

b

τ132

τ123

rmsdd,e

rmsdd,f

1.3517 −0.0311 0.1576 0.1452 −0.2382 −0.0645 −0.6400 −0.4202 −1.0604 −0.4948 −2.4871 −1.3089 −0.9949 −1.0252

−0.6413 −0.9407 −0.0175 −0.8741 1.1231 −0.9704 0.3519 0.1846 1.3912 0.7860 1.7204 0.0145 −0.3242 1.9806

2.27 5.89 0.81 0.31 2.00 1.82 0.44 0.71 2.80 2.34 2.75 3.18 1.62 14.15

0.65 1.32 0.26 0.49 1.30 1.36 0.37 0.63 0.56 0.71 2.69 0.87 1.07 3.94

lit. 13 13 17 this work 18 19 20

a

Number of tie lines. bModified UNIQUAC model. cExtended UNIQUAC model. dRoot-mean-square deviation (in mole percent). ePredicted results using binary parameters. fCorrelated results using binary and ternary parameters.

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CALCULATED RESULTS AND DISCUSSION Table 6 lists the optimized binary energy parameters aij for constituent binary systems obtained by the modified and extended UNIQUAC models, along with standard deviation between measurements and calculations: δP for pressure, δT for temperature, δx for liquid phase mole fraction, and δy for vapor phase mole fraction. The ternary parameters and the rmsd values between the experimental and calculated mole fractions of both the modified and extended UNIQUAC models are presented in Table 7. For the ternary systems, the average values of rmsd of correlated results were 0.98 mol % for the modified UNIQUAC model and 1.32 mol % for the extended UNIQUAC model.5,6 The prediction of LLE for the ternary systems was carried out

using the constituent binary parameters given in Table 6. Obviously, the correlated results obtained from the models using binary and ternary parameters are better than the predicted ones. Figure 2 displays the tie lines for the ternary system of water + DEC + methylbenzene at 298.15 K. In this triangular diagram, the measured tie lines are compared with correlated results of the modified UNIQUAC model. The three quaternary systems exhibit type 2 quaternary LLE behavior, which is composed of two ternary systems of water + methanol + methylbenzene or heptane or cyclohexane and water + methanol + DEC which is classified as type 124 and one ternary system of water + DEC + methylbenzene or heptane or cyclohexane which is classified as type 2.24 2065

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UNIQUAC models with the quaternary parameters as well as the binary and ternary parameters. The predicted results were achieved using the models with only the binary and ternary parameters. The average values of rmsd of the quaternary correlations obtained by the modified and extended UNIQUAC models were 0.85 mol % and 0.75 mol %, respectively. As can be observed in Table 8, the average deviations from the extended UNIQUAC model are smaller than those from the modified UNIQUAC model. The quaternary experimental tie lines have been plotted in Figures 3−5 and compared with correlated results of the modified UNIQUAC model for the quaternary systems of water + methanol + DEC + methylbenzene, water + methanol + DEC + heptane, and water + methanol + DEC + cyclohexane at 298.15 K. Figures 3−5 show better agreement between the experimental results and those correlated by the modified UNIQUAC model including the quaternary parameters. In order to compare the influences of the OH group in the alcohols, the experimental tie lines for the quaternary systems of (water + methanol or ethanol or propan-1-ol + DEC + heptane)17,25 were plotted in Figure 6. The OH group can affect the solubility of the alcohols in aqueous phase. In comparison

Figure 2. Experimental and calculated tie-line compositions in mole fraction for the (water + DEC + methylbenzene) system at T = 298.15 K: ●− − −●, experimental tie lines; , correlated tie lines of the modified UNIQUAC model.

Table 8 provides a summary of the quaternary calculation results of the modified and extended UNIQUAC models. The correlated results were obtained using the modified and extended

Table 8. Calculated Results for Quaternary Liquid−Liquid Equilibria at 298.15 K Na

τ2341

water + methanol + DEC + methylbenzene

30

water + methanol + DEC + heptane

29

water + methanol + DEC + cyclohexane

30

−1.9060 −2.3803c 0.0007 −1.8404 −2.7456 −2.3805

system (1 + 2 + 3 + 4)

b

τ1342

τ1243

τ1234

rmsdd,e

rmsdd,f

− 6.4794 7.7874 0.0011 −11.1739 −15.4072 −14.6216

0.5421 2.9740 0.0104 61.6934 −59.3991 1.5816

− 7.4623 7.8591 0.0032 5.4223 −13.6814 3.4778

1.48 0.51 1.20 1.11 1.01 1.23

0.87 0.49 1.20 0.99 0.55 0.76

a Number of data points. bModified UNIQUAC model. cExtended UNIQUAC model. dRoot-mean-square deviation (in mole percent). ePredicted results using binary and ternary parameters. fCorrelated results using binary, ternary and quaternary parameters.

Figure 3. Experimental and calculated tie-line compositions in mole fraction on the planes x3′ = 0.20, 0.40, 0.60, and 0.80 for the (water + methanol + DEC + methylbenzene) system at T = 298.15 K: ●− − −●, experimental tie lines; , correlated tie lines of the modified UNIQUAC model. 2066

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Figure 4. Experimental and calculated tie-line compositions in mole fraction on the planes x3′ = 0.20, 0.40, 0.60, and 0.80 for the (water + methanol + DEC + heptane) system at T = 298.15 K: ●− − −●, experimental tie lines; , correlated tie lines of the modified UNIQUAC model.

Figure 5. Experimental and calculated tie-line compositions in mole fraction on the planes x3′ = 0.20, 0.40, 0.60, and 0.80 for the (water + methanol + DEC + cyclohexane) system at T = 298.15 K: ●− − −●, experimental tie lines; , correlated tie lines of the modified UNIQUAC model.

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with ethanol and propan-1-ol, methanol more easily forms an intermolecular hydrogen bond, because its space resistance is smaller than that of ethanol and propan-1-ol. So methanol is more likely to dissolve in aqueous phase compared with ethanol and propan-1-ol, as shown in Figure 6.

CONCLUSIONS

LLE for the three quaternary systems of water + methanol + DEC + methylbenzene, water + methanol + DEC + heptane, water + methanol + DEC + cyclohexane and the relevant ternary system of water + DEC + methylbenzene were experimentally 2067

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Figure 6. Tie-line compositions in mole fraction on the planes x3′ = 0.20, 0.40, 0.60, and 0.80 for the (water + alcohol + DEC + heptane) system at T = 298.15 K: Alcohol: ■, methanol; ●, ethanol;25 ▲, propan-1-ol.17 (5) Tamura, K.; Chen, Y.; Tada, K.; Yamada, T.; Nagata, I. Representation of multicomponent liquid-liquid equilibria for aqueous and organic solutions using a modified UNIQUAC model. J. Solution Chem. 2000, 29, 463−488. (6) Nagata, I. Modification of the extended UNIQUAC model for correlating quaternary liquid-liquid equilibria data. Fluid Phase Equilib. 1990, 54, 191−206. (7) Koon, Z. S.; Phutela, R. C.; Fenby, D. V. Determination of the equilibrium constants water-methanol deuterium exchange reactions from vapour pressure measurements. Aust. J. Chem. 1980, 33, 9−13. (8) Nagata, I. Isothermal (vapour + liquid) equilibria of (methanol + toluene) and of (methanol + acetonitrile + toluene). J. Chem. Thermodyn. 1988, 20, 467−471. (9) Rodríguez, A.; Canosa, J.; Domínguez, A.; Tojo, J. Isobaric vaporliquid equilibria of diethyl carbonate with four alkanes at 101.3 kPa. J. Chem. Eng. Data 2002, 47, 1098−1102. (10) Rodríguez, A.; Canosa, J.; Domínguez, A.; Tojo, J. Isobaric phase equilibria of diethyl carbonate with five alcohols at 101.3 kPa. J. Chem. Eng. Data 2003, 48, 86−91. (11) Zhao, X.; Yang, Y. Measurement and correlation for vapor-liquid equilibrium data of diethyl carbonate-toluene binary system. Nat. Gas Chem. Ind. 2010, 35, 76−78. (12) Gmehling, J.; Onken, U. Vapor-Liquid Equilibrium Data Collection; DECHEMA: Frankfurt/Main, Germany, 1977; Vol. I, Part 2a. (13) Chen, Y.; Fu, M.; Hu, J. H. Measurement of liquid-liquid equilibria for ternary mixtures with diethyl carbonate or methyl tert-butyl ether. Chem. J. Internet 2008, 10, 48−56. (14) Sørensen, J. M.; Arlt, W. Liquid-Liquid Equilibrium Data Collection; DECHEMA: Frankfurt/Main, Germany, 1979; Vol. V, Part 1. (15) Ruiz, F.; Prats, D.; Gomis, V. Quaternary liquid-liquid equilibrium: Water-ethanol-chloroform-toluene at 25 °C. Experimental determination and graphical and analytical correlation of equilibrium data. J. Chem. Eng. Data 1985, 30, 412−416.

determined at 298.15 K. The quaternary LLE data were correlated by means of the extended and modified UNIQUAC models with the ternary and quaternary interaction parameters in addition to the binary ones, with root-mean-square deviations of less than 0.90 mol %. In comparison with the modified UNIQUAC model, the extended UNIQUAC model provided the more satisfactory prediction and correlation. The two models show an agreement with the experimental results.

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AUTHOR INFORMATION

Corresponding Author

*Fax: +86-20-85221697. E-mail: [email protected]. Funding

We are grateful to the National Scientific Research Found of China for financial support (Grant 21271088). Notes

The authors declare no competing financial interest.

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DOI: 10.1021/acs.jced.5b00048 J. Chem. Eng. Data 2015, 60, 2062−2069