Isobaric VaporâLiquid Equilibria for Binary Systems Comprising 1

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Isobaric Vapor−Liquid Equilibria for Binary Systems Comprising 1‑Chloro-2-ethylhexane, 2‑Ethyl-1-hexanol, p‑Xylene, and N‑Methylpyrrolidone (NMP) at 40.0 kPa Guoqiang Huang and Chengcheng Lv* School of Chemical Engineering and Technology, Tianjin University, Tianjin, 300072, China ABSTRACT: Isobaric vapor−liquid equilibria (VLE) of binary systems formed by 1-chloro-2-ethylhexane + 2-ethyl-1-hexanol as well as 1-chloro-2-ethylhexane or 2-ethyl-1-hexanol + p-xylene (PX), or N-methylpyrrolidone (NMP) were determined at a pressure of 40.0 kPa using a recirculating still. The Wilson, nonrandom two-liquid (NRTL), and universal quasichemical (UNIQUAC) activity coefficient models were used to describe the nonideality of the liquid phase. The vapor phase was regarded as ideal. The experimental data were checked with the Herington consistency and point consistency test methods, which showed thermodynamic consistency.

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INTRODUCTION 2-Ethylhexyl phosphonic acid mono-2-ethylhexyl ester (PC-88A) is a kind of organophosphorus extractant which is widely used to extract and separate nonferrous and rare earth metals.1−3 The synthesis of PC-88A was introduced by Zhang et al.4 During the synthesis process of PC-88A, byproducts such as 1-chloro-2-ethylhexane and 2-ethyl-1-hexanol are produced. 1-Chloro-2-ethylhexane and 2-ethyl-1-hexanol are both important chemicals,5 and vapor−liquid equilibria (VLE) data are needed for the separation of the two components. As the two chemicals have relatively high boiling points (445.40 K and 457.50 K at 101.3 kPa, respectively), it is advisable to separate them at a reduced pressure. However, as the cost of the vacuum system will be increased with the system pressure reduced, 40.0 kPa is relatively suitable for practical applications. In this work, isobaric VLE data for binary systems comprising 1-chloro-2ethylhexane, 2-ethyl-1-hexanol, p-xylene (PX) and N-methylpyrrolidone (NMP) were measured at 40.0 kPa using a recirculating still. To our knowledge, no experimental data at this pressure have been found in the open literature.6 The obtained VLE data of binary systems were tested to be thermodynamically consistent. The experimental data were correlated with the Wilson,7 nonrandom two-liquid (NRTL),8 and universal quasichemical (UNIQUAC)9 equations for the liquid-phase activity coefficients, while the vapor phase was taken to be ideal.

Guangfu Co., Ltd., Tianjin, China. All of the chemicals were checked by gas chromatography. So they were used directly in the experiment without any further treatment. The density was measured with an electronic hydrometer (MDY-2) with an uncertainty of ± 0.2 kg·m−3. The temperature of the pure liquid to be tested was measured with a Pt-100 resistance thermometer with an uncertainty of ± 0.05 K. The specifications of the chemicals used are summarized in Table 1, and the properties of the chemicals are listed in Table 2.10−15 Table 1. Specifications of the Chemicals Used chemical name 1-chloro-2-ethylhexane 2-ethyl-1-hexanol PX NMP a

Zhongda Chemical Co., Ltd. Guangfu Co., Ltd. Guangfu Co., Ltd. Guangfu Co., Ltd.

mass fraction purity

analysis method

≥ 0.993

GCa

≥ 0.997 ≥ 0.995 ≥ 0.995

GCa GCa GCa

Gas−liquid chromatography.

Apparatus and Procedure. In this work, the VLE data were determined using a modified Rogalski−Malanoski equilibrium still as described in previous papers.16,17 A schematic diagram of the apparatus is shown in Figure 1. The capacity of the still was about 60 cm3. Liquid in the still was heated by a heating rod, and the power was adjustable. The pressure was kept constant by adjusting the valve. Magnetic stirrers were used to accelerate the establishment of phase equilibrium. The

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EXPERIMENTAL SECTION Chemicals. 1-Chloro-2-ethylhexane (≥ 0.993, mass fraction) was supplied by Zhongda Chemical Co., Ltd., China. 2-Ethyl-1hexanol (≥ 0.997, mass fraction), PX (≥ 0.995, mass fraction), and NMP (≥ 0.995, mass fraction) were purchased from © 2013 American Chemical Society

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Received: July 30, 2012 Accepted: January 3, 2013 Published: January 16, 2013 279

dx.doi.org/10.1021/je300848z | J. Chem. Eng. Data 2013, 58, 279−284

Journal of Chemical & Engineering Data

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Table 2. Properties of the Pure Compoundsa compound

1-chloro-2-ethylhexane

2-ethyl-1-hexanol

PX

NMP

Tb/K (101.3 kPa) Tc/K Pc/MPa ρ/kg·m−3 (298.15 K)

445.40b 623.46c 2.463c 877.05b

457.50d 641.0e 2.800e 828.910f

411.38g 616.26g 3.5110g 856.5g

476.50h 721.8i 4.52i 1028.25j

Critical temperature Tc, critical pressure Pc. bMeasured in this work. Tb, measured with the equilibrium still, u(T) = ± 0.05 K, u(ρ) = ± 0.2 kg·m−3. Predicted from the pure component properties. dTaken from ref 5. eTaken from ref 10. fTaken from ref 11. gTaken from ref 12. hTaken from ref 13. iTaken from ref 14. jTaken from ref 15. a c

Table 3. Experimental Vapor Pressuresa of 1-Chloro-2-ethylhexane

a

T/K

P/kPa

T/K

P/kPa

445.40 441.45 436.65 431.15 425.20 419.05 411.90

101.3 91.6 80.7 69.6 59.0 49.4 39.9

405.85 403.50 399.50 394.25 385.85 375.35 371.05

33.2 30.8 27.1 22.8 17.1 11.7 9.9

u(T) = ± 0.05 K, and u(P) = ± 0.1 kPa.

Figure 1. Schematic diagram of the VLE apparatus: 1, heating rod; 2, vacuum chamber; 3, platinum resistance thermometer; 4, equilibrium chamber; 5, vapor sampling point; 6, liquid sampling point; 7, magnetic stirrer; 8, condenser; 9, magnetic rotor; 10, reference manometer; 11, buffer tank; 12, valve; 13, vacuum pump; 14, U-style manometer.

temperatures were measured with a calibrated platinum resistance thermometer with an uncertainty of ± 0.05 K. A precise U-tube mercury manometer with an uncertainty of ± 0.1 kPa was used to determine the pressure. Equilibrium conditions were assumed when constant temperature and pressure were obtained for 45 min or longer. The gas chromatography (GC 7890A, Agilent Technologies) equipped with a flame ionization detector (FID) was used to analyze the liquid and condensed vapor samples. The column was a DB-17 capillary column (30 m × 0.25 mm × 0.25 μm, Agilent), and the carrier gas was nitrogen flowing at 25 mL· min−1. The operating conditions were as follows: split ratio, 40:1; injector temperature, 513.15 K; detector temperature, 513.15 K; oven temperature, started at 353.15 K, ascending at the rate of 10 K·min−1 until 473.15 K, running 12 min totally; sample volume, 0.2 μL. The gas chromatography was calibrated with standard solutions that were prepared gravimetrically by an electronic balance with an uncertainty of ± 0.0001 g. Every sample was checked by gas chromatography for at least three times to ensure that the absolute deviations of vapor and liquid mole fraction measurements from the mean values were no more than 0.005.

Figure 2. y1−x1 diagram for the benzene (1) + toluene (2) system at 101.3 kPa. ■, experimental data; □, literature data.

Vapor−Liquid Equilibria Data. To test the performance of the equilibrium still, binary VLE for the system of benzene (1) + toluene (2) were measured at 101.3 kPa. As is shown in Figure 2, the experimental data are in good agreement with those reported by Jin et al.,18 thus verifying that the equilibrium still is reliable. The VLE data for the binary systems obtained at 40.0 kPa are listed in Tables 5 to 9, together with the experimental values of activity coefficients γi. The T−x−y diagrams are shown in Figure 3. The experimental liquid-phase activity coefficients of component i were calculated using the following equation:

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RESULTS AND DISCUSSION Pure Component Vapor Pressures. The pure component vapor pressures of 1-chloro-2-ethylhexane were determined, and the data are shown in Table 3. The Antoine equation was used to correlate the experimental data, and the average absolute deviation (AAD) between the measured data and those correlated by the Antoine equation was 0.04 kPa as shown in Table 4. Antoine parameters for 2-ethyl-1-hexanol, PX, and DMP were obtained from previous papers and are shown in Table 4, too.

γi =

Pyi Pisxi

(1)

where yi and xi are the molar fractions of component i in the vapor and liquid phases, respectively, P is the total pressure, and Psi is the saturation vapor pressure of the pure liquid i at temperature T. In eq 1, the vapor phase can be regarded as ideal at low experimental pressures (Pr < 0.03).19 For binary liquid systems, when intermolecular interaction between the identical molecules is larger than that between 280



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Table 4. Antoine Parametersa of the Pure Components component 1-chloro-2-ethylhexane 2-ethyl-1-hexanold PXe NMPf

c

range T/K

A

B

C

AAD(P)b/kPa

371.15−445.40 347.22−456.70 300.15−439.15 380.73−475.72

15.1580 13.8473 14.0813 14.65738

4343.3147 3052.9515 3346.646 4112.28

−33.272 −126.690 −57.840 −66.866

0.04

ln(P/kPa) = A − B/(C + T/K). bAverage absolute deviation in vapor pressure: AAD(P) = (1/N)∑Ni=1|Pexp − Pcal i i | (N, number of data points). Antoine parameters determined from experimental data. dTaken from ref 5. eTaken from ref 12. fTaken from ref 13.

a c

Table 7. VLE Data and Activity Coefficients (γ) for the Binary System of PX (1) + 2-Ethyl-1-hexanol (2) at 40 kPaa

Table 5. VLE Data and Activity Coefficients (γ) for the Binary System of 1-Chloro-2-ethylhexane (1) + 2-Ethyl-1hexanol (2) at 40 kPaa

a

T/K

x1

y1

γ1

412.05 412.00 411.95 411.95 412.00 412.05 412.15 412.25 412.55 413.35 413.95 414.60 416.00 417.50 418.95 420.95 422.35 424.50 427.20

1.000 0.987 0.977 0.967 0.955 0.931 0.902 0.870 0.808 0.680 0.613 0.553 0.449 0.358 0.278 0.197 0.141 0.071 0.000

1.000 0.987 0.977 0.967 0.955 0.934 0.908 0.884 0.839 0.752 0.703 0.667 0.587 0.502 0.422 0.335 0.262 0.149 0.000

1.001 1.002 1.003 1.004 1.002 1.003 1.005 1.010 1.023 1.064 1.084 1.118 1.164 1.194 1.240 1.311 1.371 1.456

γ2 1.759 1.745 1.720 1.706 1.663 1.597 1.520 1.416 1.266 1.227 1.162 1.110 1.089 1.066 1.027 1.016 1.005 1.001

a

Table 6. VLE Data and Activity Coefficients (γ) for the Binary System of PX (1) + 1-Chloro-2-ethylhexane (2) at 40 kPaa

a

x1

y1

γ1

379.85 381.15 382.15 383.80 386.60 388.95 391.95 394.75 398.80 403.00 405.70 408.30 410.05 412.05

1.000 0.948 0.900 0.841 0.748 0.667 0.569 0.483 0.364 0.240 0.172 0.104 0.053 0.000

1.000 0.984 0.966 0.943 0.900 0.855 0.789 0.712 0.592 0.438 0.332 0.210 0.111 0.000

1.001 0.996 0.998 0.989 0.973 0.964 0.952 0.932 0.913 0.909 0.890 0.869 0.860

x1

y1

γ1

1.000 0.946 0.886 0.760 0.667 0.583 0.465 0.381 0.299 0.215 0.152 0.086 0.025 0.000

1.000 0.985 0.968 0.936 0.912 0.882 0.832 0.783 0.715 0.617 0.505 0.341 0.117 0.000

1.001 1.002 1.007 1.043 1.080 1.109 1.166 1.210 1.250 1.294 1.319 1.342 1.339

γ2 1.756 1.666 1.397 1.250 1.200 1.124 1.085 1.061 1.031 1.031 1.018 1.013 1.001

u(T) = ± 0.05 K, u(P) = ± 0.1 kPa, and u(x) = u(y) = ± 0.005.

Table 8. VLE Data and Activity Coefficients (γ) for the Binary System of 1-Chloro-2-ethylhexane (1) + NMP (2) at 40 kPaa


T/K

T/K 379.85 381.05 382.40 385.10 387.35 389.80 393.70 397.15 401.30 406.60 411.30 417.35 423.95 427.20

γ2 0.833 0.906 0.898 0.904 0.916 0.932 0.964 0.973 0.980 0.982 0.989 0.998 1.001

a

T/K

x1

y1

γ1

412.05 412.45 413.25 414.85 416.55 417.75 420.10 423.55 428.00 431.70 434.65 438.00 439.60 441.80

1.000 0.898 0.808 0.651 0.532 0.465 0.352 0.245 0.151 0.095 0.061 0.029 0.016 0.000

1.000 0.919 0.856 0.774 0.711 0.676 0.617 0.530 0.415 0.313 0.229 0.123 0.073 0.000

1.001 1.012 1.023 1.094 1.169 1.226 1.383 1.541 1.725 1.875 1.968 2.032 2.095

γ2 2.015 1.843 1.513 1.361 1.284 1.158 1.091 1.047 1.028 1.016 1.010 1.005 1.000


2-ethyl-1-hexanol (2), and 1-chloro-2-ethylhexane (1) + NMP (2) exhibit a positive deviation from Raoult’s law (Tables 5, 7 and 8, γi > 1), while the systems of PX (1) + 1-chloro-2ethylhexane (2) and 2-ethyl-1-hexanol (1) + NMP (2) exhibit a negative deviation from Raoult’s law (Tables 6 and 9, γi < 1). The results can be explained by the classification of molecules provided by Ewell et al.20 The classification is based on the potential for association or solvation due to hydrogen bond formation. According to the classification, both PX and 1-chloro-2-ethylhexane belong to the category V, 2-ethyl-1hexanol is classified as the category II, and NMP belongs to the category III. When PX or 1-chloro-2-ethylhexane is added to


different ones, a positive deviation from Raoult’s law is shown. On the contrary, if intermolecular interaction between different molecules is larger than that between the identical ones, a negative deviation from Raoult’s law appears. It can be seen from Tables 5 to 9 that the binary systems of 1-chloro-2-ethylhexane (1) + 2-ethyl-1-hexanol (2), PX (1) + 281



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make the function (x1 − y1) = f(x1) equals zero.21 A polynomial equation T = f(x1) was obtained by fitting the experimental results around the azeotropic point, and the azeotropic temperature can be determined by using the calculated azeotropic composition value, x1. The azeotropic molar fraction of 1-chloro-2-ethylhexane is calculated to be 0.9690, and the azeotropic temperature is 411.94 K. Consistency Tests of Experimental Data. The Herington consistency test22 based on the Gibbs−Duhem theorem was used to verify the experimental data. Herington suggests that if (D − J) < 10, the experimental data are considered to be thermodynamically consistent. The checking results for the systems of 1-chloro-2-ethylhexane (1) + 2-ethyl-1-hexanol (2), PX (1) + 1-chloro-2-ethylhexane (2), PX (1) + 2-ethyl-1hexanol (2), 1-chloro-2-ethylhexane (1) + NMP (2), and 2-ethyl-1-hexanol (1) + NMP (2) are 8.12, −6.28, 4.61, 4.93, and −1.76, respectively, which indicate that the experimental data are thermodynamically consistent. The results have also been tested using the point consistency method of Van Ness et al.23 According to the test, the experimental data are consistent if the average absolute deviation between measured and calculated vapor molar fractions of component i is less than 0.01. The results of this test for the binary systems of 1-chloro-2-ethylhexane (1) + 2-ethyl-1hexanol (2), PX (1) + 1-chloro-2-ethylhexane (2), PX (1) + 2ethyl-1-hexanol (2), 1-chloro-2-ethylhexane (1) + NMP (2), and 2-ethyl-1-hexanol (1) + NMP (2) are 0.0049, 0.0020, 0.0059, 0.0097, and 0.0038, respectively. These results indicate that all of the experimental data are thermodynamically consistent. Data Regression. The experimental data were correlated with the Wilson, NRTL, and UNIQUAC models by minimizing the following objective function Q24

Table 9. VLE Data and Activity Coefficients (γ) for the Binary System of 2-Ethyl-1-hexanol (1) + NMP (2) at 40 kPaa

a

T/K

x1

y1

γ1

427.20 429.55 430.85 432.90 435.55 436.75 438.25 439.10 439.70 440.35 441.05 441.40 441.60 441.80

1.000 0.888 0.828 0.743 0.621 0.566 0.482 0.417 0.362 0.285 0.198 0.123 0.073 0.000

1.000 0.954 0.915 0.853 0.735 0.668 0.571 0.492 0.420 0.327 0.225 0.141 0.084 0.000

1.001 0.994 0.979 0.952 0.900 0.863 0.827 0.802 0.773 0.752 0.727 0.725 0.724

γ2 0.595 0.689 0.744 0.843 0.889 0.919 0.943 0.967 0.981 0.987 0.991 0.993 1.000


2-ethyl-1-hexanol to form a solution, there are H-bonds broken only and no new H-bonds produced. As a result, a positive deviation is shown. While for the solution of 2-ethyl-1-hexanol and NMP, there are both H-bonds broken and new H-bonds produced. As the interaction of new H-bonds produced is larger than that of H-bonds broken, a negative deviation from Raoult’s law appears. For the system of PX (1) + 1-chloro-2-ethylhexane (2), it is close to ideal solution, as a result, only a slight negative deviation is shown. There are no H-bonds produced or broken for the system of 1-chloro-2-ethylhexane (1) + NMP (2); a positive deviation is shown as classified by Ewell et al.20 For 1-chloro-2-ethylhexane (1) + 2-ethyl-1-hexanol (2) system, a minimum boiling azeotrope exists. The azeotropic composition for the system was obtained by determining the x1 values that

Table 10. Correlated Interaction Parameters, Average Absolute Deviations (AADs), and the Percent Average Relative Deviations (ARD %) between Experimental and Calculated Values model

A12a/K

A21a/K

Wilson NRTL UNIQUAC

11.4032 333.8720 −156.0342

−256.2882 −84.9401 96.9529

Wilson NRTL UNIQUAC

96.9945 41.7916 59.5622

−27.2760 −110.9864 −40.5318

Wilson NRTL UNIQUAC

67.6830 425.6263 −62.80361

−323.9607 −158.5822 22.6799

Wilson NRTL UNIQUAC

−185.8592 189.2190 −262.0621

−202.9671 180.1778 123.0553

Wilson NRTL UNIQUAC

553.1880 441.3683 −221.8083

−846.8295 −516.2335 216.1730

α

AADb(y)

AAD(T)/K

1-Chloro-2-ethylhexane (1) + 2-Ethyl-1-hexanol (2) 0.0049 0.040 0.3 0.0048 0.040 0.0049 0.040 PX (1) + 1-Chloro-2-ethylhexane (2) 0.0019 0.146 0.3 0.0020 0.146 0.0017 0.149 PX (1) + 2-Ethyl-1-hexanol (2) 0.0058 0.030 0.3 0.0059 0.030 0.0058 0.029 1-Chloro-2-ethylhexane (1) + NMP (2) 0.0098 0.076 0.3 0.0097 0.076 0.0102 0.081 2-Ethyl-1-hexanol (1) + NMP (2) 0.0028 0.112 0.3 0.0034 0.078 0.0112 0.293

AAD(P)/kPa

ARDc % (γ1)

ARD % (γ2)

0.005 0.005 0.005

1.20 1.21 1.24

1.61 1.60 1.64

0.019 0.019 0.019

0.76 0.78 0.65

1.41 1.40 1.57

0.103 0.111 0.111

1.73 1.74 1.74

3.02 3.05 2.95

0.0089 0.0087 0.0093

2.23 2.20 2.32

3.48 3.44 3.61

0.018 0.014 0.037

1.40 1.68 4.47

0.72 1.13 3.15

The interaction parameters for various models: Wilson, Aij = (λij − λji)/R; NRTL, Aij = (gij − gji)/R; UNIQUAC, Aij = (Uij − Uji)/R. bAAD(y) = c N exp cal exp − ycal (1/N)∑Ni=1|yexp i i | (N, number of data points). ARD % (γi) = (100/N)∑j=1(|yi,j − yi,j |/γi,j ) (N, number of data points). a

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Figure 3. T−x1−y1 diagram for the binary systems at 40 kPa. ■, x1 measured; □, y1 measured; , NRTL model; (a) 1-chloro-2-ethylhexane (1) + 2-ethyl-1-hexanol (2); (b) PX (1) + 1-chloro-2-ethylhexane (2); (c) PX (1) + 2-ethyl-1-hexanol (2); (d) 1-chloro-2-ethylhexane (1) + NMP (2); (e) 2-ethyl-1-hexanol (1) + NMP (2).

⎡⎛ exp cal ⎞2 ⎛ P exp − P cal ⎞2 j j ⎢⎜ Tj − Tj ⎟ ⎟ + ⎜⎜ Q = ∑ ⎢⎜ ⎟ ⎟ σT σP ⎠ ⎝ ⎠ j = 1 ⎣⎝

average absolute deviation (AAD), and the percent average relative deviation (ARD %) between the experimental and the calculated values are listed in Table 10. It can be seen from Table 10 and Figure 3 that all of the Wilson, NRTL, and UNIQUAC models fit the systems well. The ADD of the vapor molar fraction, bubble-point temperature, and pressure calculated with the correlated parameters are no more than 0.0112, 0.293 K, and 0.111 kPa, respectively. The ARD % for the activity coefficients of the measured binary systems are no more than 4.47 and 3.61, respectively. The UNIQUAC model shows larger deviation for the system of 2-ethyl-1-hexanol (1) + NMP (2) compared with the Wilson and NRTL model. As for the other four binary systems, the Wilson, NRTL, and UNIQUAC models have almost the same calculation results.

N

⎛ x exp − x cal ⎞2 j,i j,i ⎟ + + ∑ ⎜⎜ ⎟ σ x , i ⎠ i=1 ⎝ C

⎛ y exp − y cal ⎞2 ⎤ j,i ⎟ ⎥ ∑ ⎜⎜ j ,i ⎟⎥ σy , i i=1 ⎝ ⎠ ⎥⎦ C

(2)

where N is the number of experimental data; C is the number of components; σT, σP, σx, and σy are estimated standard deviations for T, P, x, and y, respectively. The regression was carried out using the Aspen Plus V7.0 chemical process simulator. Three parameters were used for the NRTL activity coefficient model, and two parameters were used for the Wilson and UNIQUAC models. The parameter α which is taken into account the nonrandomness of the solution in the NRTL model was set as 0.3. The interaction parameters, the

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CONCLUSIONS The isobaric VLE data of the binary systems 1-chloro-2-ethylhexane (1) + 2-ethyl-1-hexanol (2), PX (1) + 1-chloro-2-ethylhexane (2), 283



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(14) Ambrose, D.; Tsonopoulos, C.; Nikitin, E. D. Vapor− Liquid Critical Properties of Elements and Compounds. 11. Organic Compounds Containing B + O; Halogens + N, + O, + O + S, + S, + Si; N + O; and O + S, + Si. J. Chem. Eng. Data 2009, 54, 669−689. (15) Ye, W.; Shen, R.; Liu, W.; Chen, J. Densities and Volumetric Properties of N-methyl-2-pyrrolidone with Aromatic Hydrocarbon at Different Temperature. J. Chem. Thermodyn. 2007, 39, 115−122. (16) Kurihara, K.; Minoura, T.; Takeda, K.; Kojima, K. Isothermal Vapor-Liquid Equilibria for Methanol + Ethanol + Water, Methanol + Water, and Ethanol + Water. J. Chem. Eng. Data 1995, 40, 679−684. (17) Kamihama, N.; Matsuda, H.; Kurihara, K.; Tochigi, K.; Oba, S. Isobaric Vapor−Liquid Equilibria for Ethanol + Water + Ethylene Glycol and Its Constituent Three Binary Systems. J. Chem. Eng. Data 2012, 57, 339−344. (18) Jin, Z.; Hu, A.; Liu, K. VLE of Binary and Ternary Systems for BTX Mixtures. Chem. Eng. (China) 1991, 19, 56−60. (19) Mohsen-Nia, M.; Memarzadeh, M. Isobaric Vapor-Liquid Equilibria of Heptane + 1-Butanol and Heptane + 1-Pentanol Systems at (53.3 and 91.3) kPa. J. Chem. Eng. Data 2010, 55, 2140−2144. (20) Ewell, R. H.; Harrison, J. M.; Berg, L. Azeotropic Distillation. Ind. Eng. Chem. 1944, 36, 871−875. (21) Chen, R.; Zhong, L.; Xu, C. Isobaric Vapor−Liquid Equilibrium for Binary Systems of Toluene + Ethanol and Toluene + Isopropanol at (101.3, 121.3, 161.3, and 201.3) kPa. J. Chem. Eng. Data 2012, 57, 155−165. (22) Herington, E. Tests for the Consistency of Experimental Isobaric Vapor-Liquid Equilibrium Data. J. Inst. Petrol. 1951, 37, 457− 470. (23) Van Ness, H. C.; Byer, S. M.; Gibbs, R. E. Vapor-Liquid Equilibrium: Part I. An Appraisal of Data Reduction Methods. AIChE J. 1973, 19, 238−244. (24) Prausnitz, J. M.; Anderson, F.; Grens, E.; Eckert, C.; Hsieh, R.; O’Connell, J. Computer Calculations for Multicomponent Vapor-Liquid and Liquid-Liquid Equilibria; Prentice-Hall: Englewood Cliffs, NJ, 1980.

PX (1) + 2-ethyl-1-hexanol (2), 1-chloro-2-ethylhexane (1) + NMP (2), and 2-ethyl-1-hexanol (1) + NMP (2) were measured at 40.0 kPa. The experimental data were checked with the Herington method and point consistency test method, which showed good thermodynamic consistency. The Wilson, NRTL, and UNIQUAC activity coefficient models were used to correlate the experimental data. The results have shown that all of the models agree well with the experimental data. Moreover, the mixture of 1-chloro-2-ethylhexane and 2-ethyl-1-hexanol can form an azeotrope at testing pressure.

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AUTHOR INFORMATION

Corresponding Author

*Telephone no.: 86-22-27891125. Fax no.: 86-22-27891125. E-mail: [email protected]. Funding

Financial support from Zhongda Chemical Co., Ltd., China is gratefully acknowledged. Notes

The authors declare no competing financial interest.

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REFERENCES

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