Evaluation of Diethyl Carbonate and Methyl Isobutyl Ketone as

Article pubs.acs.org/jced

Evaluation of Diethyl Carbonate and Methyl Isobutyl Ketone as Entrainers for the Separation of 1‑Hexene and n‑Hexane Beatriz Marrufo,† Jordi Pla-Franco,‡ Estela Lladosa,‡ and Sonia Loras*,‡ †

Departamento de Ingeniería Química Básica, Universidad del Zulia, 4011, Maracaibo, Venezuela Departamento de Ingeniería Química, Escuela Técnica Superior de Ingeniería, Universitat de València, 46100 Burjassot, Valencia, Spain

‡

ABSTRACT: Diethyl carbonate and methyl isobutyl ketone are tested as possible entrainers for separating 1-hexene and n-hexane by extractive distillation. For this purpose, isobaric vapor−liquid equilibrium (VLE) data at 100 kPa have been obtained for the two ternary systems formed by the two hydrocarbons and one of the selected solvents: 1-hexene + n-hexane + diethyl carbonate and 1-hexene + n-hexane + methyl isobutyl ketone. VLE data for the following constituent binary systems have also been determined: 1-hexene + diethyl carbonate, n-hexane + diethyl carbonate, 1-hexene + methyl isobutyl ketone, and finally n-hexane + methyl isobutyl ketone. All binary systems present moderate positive deviations from Raoult’s law, and neither binary systems nor ternary systems show an azeotrope. The local composition models Wilson, UNIQUAC, and NRTL have been used for correlating VLE data and evaluating solvent effects.

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INTRODUCTION α-Olefins like 1-hexene are mainly used in the polymer, surfactant, and detergent industries. The different production routes for α-olefins include a stream of final products with a large quantity of similar components: olefin isomers (internal, branched, cyclic, and diolefins) and paraffins.1 The recovery and especially the purifications of α-olefins from these streams is difficult because the boiling points of these compounds are very similar. The separation of these hydrocarbons by conventional distillation is not a recommended method because is very costly due to the high reflux ratios and large number of stages necessary. However, extractive distillation can be a good alternative since in it a solvent called entrainer is used to modify the relative volatility of the components to be separated. The selection of a proper solvent is very important to ensure an effective and economical design of a separation by extractive distillation. The choice of the entrainer must be made from complete and accurate vapor− liquid equilibrium (VLE) data of the ternary systems formed by the two components to be separated and the possible solvent.

The present work is part of the thermodynamic research on the selection of green solvents for the separation of paraffins and olefins by extractive distillation.2−6 In this study, 1-hexene and n-hexane are taken to represent olefins and paraffins mixtures, and the feasibility of diethyl carbonate and methyl isobutyl ketone as possible entrainers is investigated. These two solvents were previously studied in the separation of cyclohexane and cyclohexene by extractive distillation with satisfactory results.4,5 Table 2. Denstiy d and Normal Boiling Point Tb of Pure Components d (298.15 K)a (kg·m−3) component

chemical name n-hexane 1-hexene diethyl carbonate methyl isobutyl ketone a

purification method

Fluka Aldrich Fluka

0.9950 0.9900 0.9900

none none distillation

AcrosOrganics

0.9950

none

source

final mass fraction purity

analysis method

0.9998

GCa GCa GCa

lit.

exptl

lit.

669.34

668.4018

336.48

336.6312

n-hexane

655.10

654.9018

methyl isobutyl ketone

Table 1. Specifications of Chemical Samples initial mass fraction purity

exptl

1-hexene diethyl carbonate a

Tb (101.3 kPa)b (K)

969.08 796.03

341.79

341.8812

969.10

8

399.27

399.9512

796.10

18

388.78

388.8212

u(T) = 0.01 K. u(P) = 0.1 kPa. u(d) = 0.5 kg·m−3; u(Tb) = 0.02 K. b

In this work, VLE data at 100 kPa have been measured for the two ternary systems 1-hexene (1) + n-hexane (2) + diethyl carbonate (3a) and 1-hexene (1) + n-hexane (2) + methyl isobutyl ketone (3b) and constituent binary systems. Previously,7 VLE data for the binary system 1-hexene (1) + n-hexane (2) were reported. Isobaric VLE data of binary hexane + diethyl carbonate system was obtained by Rodriguez et al.8 However, for the other

GCa

Received: October 25, 2016 Accepted: February 22, 2017

Gas chromatography. © XXXX American Chemical Society

A

DOI: 10.1021/acs.jced.6b00905 J. Chem. Eng. Data XXXX, XXX, XXX−XXX

Journal of Chemical & Engineering Data

Article

Table 3. Experimental Vapor−Liquid Equilibrium Data for the Binary System 1-Hexene (1) + Diethyl Carbonate (3a) at 100.0 kPaa: Temperature (T), Mole Fraction of Liquid Phase (xi), Mole Fraction of Vapor Phase (yi), and Activity Coefficients (γi)

a

Table 5. Experimental Vapor−Liquid Equilibrium Data for the Binary System 1-Hexene (1) + Methyl Isobutyl Ketone (3b) at 100.0 kPaa: Temperature (T), Mole Fraction of Liquid Phase (xi), Mole Fraction of Vapor Phase (yi), and Activity Coefficients (γi)

T (K)

x1

y1

γ1

γ3a

T (K)

x1

y1

γ1

γ3b

393.64 390.60 384.58 379.68 376.08 371.13 365.85 360.84 357.41 354.29 351.69 349.56 347.65 346.10 344.39 342.91 341.73 340.47 339.05 337.61 336.87

0.022 0.037 0.072 0.101 0.132 0.171 0.223 0.289 0.339 0.394 0.457 0.513 0.562 0.615 0.672 0.727 0.776 0.827 0.885 0.945 0.979

0.155 0.250 0.404 0.494 0.572 0.648 0.719 0.785 0.821 0.853 0.880 0.900 0.915 0.925 0.937 0.945 0.955 0.966 0.975 0.988 0.995

1.611 1.648 1.561 1.521 1.465 1.443 1.400 1.342 1.310 1.274 1.217 1.177 1.153 1.114 1.085 1.056 1.036 1.020 1.004 0.996 0.990

1.003 0.989 0.979 1.002 0.987 1.003 1.024 1.024 1.040 1.048 1.054 1.064 1.084 1.158 1.223 1.362 1.426 1.469 1.725 1.840 2.072

384.11 379.23 374.26 370.43 366.44 362.29 358.87 356.54 354.30 351.35 349.39 347.62 345.79 344.59 343.05 341.80 340.60 339.51 338.35 337.33 336.86

0.029 0.064 0.102 0.137 0.179 0.234 0.283 0.324 0.367 0.429 0.480 0.532 0.587 0.644 0.692 0.746 0.801 0.853 0.909 0.959 0.982

0.138 0.281 0.414 0.506 0.584 0.664 0.713 0.750 0.782 0.825 0.851 0.862 0.885 0.897 0.915 0.926 0.944 0.957 0.973 0.989 0.997

1.352 1.390 1.441 1.437 1.401 1.353 1.313 1.284 1.255 1.228 1.196 1.149 1.127 1.078 1.070 1.042 1.026 1.009 0.997 0.991 0.989

1.000 0.998 0.985 0.974 0.980 0.974 0.997 0.999 1.007 0.997 1.001 1.099 1.112 1.210 1.224 1.356 1.374 1.491 1.584 1.493 0.945

u(T) = 0.02 K, u(p) = 0.05 kPa, and u(x1) = u(y1) = 0.005.

a

Table 4. Experimental Vapor−Liquid Equilibrium Data for the Binary System n-Hexane (2) + Diethyl Carbonate (3a) at 100.0 kPaa: Temperature (T), Mole Fraction of Liquid Phase (xi), Mole Fraction of Vapor Phase (yi), and Activity Coefficients (γi)

a

T (K)

x2

y2

γ2

γ3a

394.53 389.82 382.53 373.85 368.83 364.08 360.94 358.40 356.03 354.17 352.30 350.65 349.42 347.87 346.86 345.75 344.82 343.88 343.05 342.40 341.65

0.015 0.036 0.074 0.130 0.181 0.234 0.281 0.326 0.379 0.429 0.483 0.542 0.594 0.663 0.713 0.772 0.821 0.869 0.914 0.946 0.983

0.129 0.264 0.441 0.596 0.681 0.746 0.781 0.810 0.833 0.857 0.868 0.885 0.898 0.915 0.928 0.935 0.946 0.957 0.969 0.979 0.993

2.377 2.226 2.107 1.966 1.814 1.725 1.628 1.553 1.461 1.395 1.320 1.255 1.202 1.146 1.112 1.068 1.043 1.025 1.011 1.005 1.003

1.000 0.993 0.982 1.001 0.995 1.000 1.028 1.044 1.088 1.087 1.190 1.247 1.309 1.398 1.447 1.719 1.889 2.135 2.426 2.688 2.937


Table 6. Experimental Vapor−Liquid Equilibrium Data for the Binary System n-Hexane (2) + Methyl Isobutyl Ketone (3b) at 100.0 kPaa: Temperature (T), Mole Fraction of Liquid Phase (xi), Mole Fraction of Vapor Phase (yi), and Activity Coefficients (γi)


binary systems and for the ternary systems, VLE data have not been published before.

a

B

T (K)

x2

y2

γ2

γ3b

384.37 381.08 377.27 373.34 370.09 366.90 362.79 358.60 356.65 354.20 352.46 350.92 349.31 347.95 346.79 345.83 344.85 343.87 343.03 342.17 341.75

0.022 0.045 0.074 0.108 0.137 0.172 0.230 0.300 0.345 0.404 0.453 0.503 0.564 0.622 0.676 0.730 0.786 0.842 0.894 0.951 0.980

0.119 0.228 0.340 0.438 0.508 0.558 0.640 0.721 0.757 0.787 0.816 0.824 0.848 0.860 0.879 0.897 0.914 0.931 0.950 0.974 0.989

1.853 1.859 1.832 1.766 1.741 1.643 1.558 1.496 1.436 1.361 1.318 1.250 1.199 1.146 1.113 1.081 1.052 1.029 1.014 1.002 0.999

1.008 0.994 0.981 0.978 0.979 1.015 1.018 1.000 0.996 1.045 1.047 1.165 1.216 1.358 1.430 1.515 1.657 1.869 2.086 2.428 2.559

u(T)= 0.02 K, u(p) = 0.05 kPa, and u(x2) = u(y2) = 0.005. DOI: 10.1021/acs.jced.6b00905 J. Chem. Eng. Data XXXX, XXX, XXX−XXX


Article

Figure 1. Experimental VLE data for the system 1-hexene (1) + diethyl carbonate (3a) at 100.0 kPa: ●, experimental data; solid line, smoothed data using the NRTL model with the parameters given in Table 9.

Figure 3. Experimental VLE data for the system 1-hexene (1) + methyl isobutyl ketone (3b) at 100.0 kPa: ●, experimental data; solid line, smoothed data using the NRTL model with the parameters given in Table 9.

Figure 2. Experimental VLE data for the system n-hexane (2) + diethyl carbonate (3a) at 100.0 kPa: ●, experimental data; ○, data from Rodriguez et al.;8 solid line, smoothed data using the NRTL model with the parameters given in Table 9.

Figure 4. Experimental VLE data for the system n-hexane (2) + methyl isobutyl ketone (3b) at 100.0 kPa: ●, experimental data; solid line, smoothed data using the NRTL model with the parameters given in Table 9.

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EXPERIMENTAL SECTION Chemicals. The chemicals n-hexane (>0.995 mass fraction) and diethyl carbonate (≥0.995 mass fraction, GC grade) were supplied by Fluka, the chemical 1-hexene (>0.99 mass fraction) was supplied by Sigma-Aldrich, and methyl isobutyl ketone (≥0.995 mass fraction, for analysis) was supplied by AcrosOrganics. Diethyl carbonate was treated by batch multistage distillation process in a Fischer SPALTROHR HMS-500 column to a purity of 99.98%. The other chemicals were used without purifying since the analytical method used did not detect impurities. The specifications of used chemicals are summarized in Table 1. Experimental densities were obtained using an Anton

Paar DMA 55 densimeter with an uncertainty of 0.5 kg·m−3. All measurements were made at 298.15 K controlling the temperature by means of a thermostated bath (uncertainty of 0.01 K). The experimental values of the densities and the boiling points are listed in Table 2 together with those reported in the literature. Apparatus and Procedure. The VLE data and the vapor pressure of the pure compounds were measured with a dynamic still (Pilodist VLE 100 D) in which the liquid and the vapor phases are recirculated, and it is equipped with a Cottrell pump. The details of controlling and measuring the pressure and the temperature are given in a previous work.2 The uncertainties for C



Article

Table 7. Vapor Pressure Parametersa compound

Ai

Bi

Ci

1-hexene (1)b n-hexane (2)b diethyl carbonate (3a)c methyl isobutyl ketone (3b)d

15.1210 12.8239 14.9327 14.1959

3433.84 2178.19 3616.95 3167.41

−9.47 −76.39 −48.60 −58.11

pressure were observed to be constant along the time, several samples of a very small volume (0.2 μL) of liquid and condensed vapor were continuously analyzed until to reach a difference less than 0.001 in the mole fractions between two samples of a same phase. Analysis. Compositions of the liquid and condensed phases were determined using a Varian CP-3800 gas chromatograph (GC). A flame ionization detector was used together with a 30 m, 0.25 mm i.d. capillary column CP-Wax 52 CB. The GC response peaks were treated with Varian Star No. 1 for MS Windows. The column temperature was 403.15 K for the systems with diethyl carbonate and 353.15 K for the systems with methyl isobutyl ketone. The detector and injector temperatures were 473.15 and 493.15 K, respectively, for all systems. Under these conditions very good peak separation was obtained, and gravimetrically prepared standard solutions were analyzed for calibrating the chromatographic response in order to convert the peak area ratio into the mass composition of the sample. The average absolute deviation in the mole fraction was usually less than 0.001.

a

Vapor pressure equation: ln P° (kPa) = A + B/(T(K) + C). Parameters obtained in ref 7. cParameters obtained in ref 5. d Parameters obtained in ref 4. b

Table 8. Consistency Test Statistics for the Binary Systems 1-Hexene (1) + Solvent (3) and n-Hexane (2) + Solvent (3) system i + solvent (j)

A1a

A2a

A3a

100 AAD yib

AAD Pc/kPa

1 + diethyl carbonate (3a) 2 + diethyl carbonate (3a) 1 + methyl isobutyl ketone (3b) 2 + methyl isobutyl ketone (3b)

0.5644 0.9339 0.4754

0.1106 0.1255 0.1086

0.0321 −0.0331

0.348 0.440 0.502

0.487 0.126 0.563

0.7683

0.1462

0.0229

0.229

0.640

■

a Legendre polynomial parameters. bAverage absolute deviation in vapor-phase composition. cAverage absolute deviation in pressure.

RESULTS AND DISCUSSION Binary Systems. The temperature T and the liquid-phase xi and vapor-phase yi mole fractions at 100.0 kPa for the systems 1-hexene (1) + diethyl carbonate (3a), n-hexane (2) + diethyl carbonate (3a), 1-hexene (1) + methyl isobutyl ketone (3b), and n-hexane (2) + methyl isobutyl ketone (3b) are reported in Tables 3−6 and plotted in Figures 1−4. To compare the data acquired in this work to those published by Rodriguez et al.8 have been plotted together in Figure 2. The activity coefficients

pressure and temperature are estimated to be 0.05 kPa and 0.02 K, respectively. To determine each VLE point, the first step was to set and keep the pressure at a value of 100.0 kPa using an electrovalve and a vacuum pump and then turn on the heating and stirring systems of the liquid mixture. Then, when the values of temperature and

Table 9. Parameters and Correlation Statistics for Different GE Models for the Ternary Systems 1-Hexene (1) + n-Hexane (2) + Solvent (3) bubble point model Wilsonc

NRTL

UNIQUACf

Wilsonc

NRTL

UNIQUACf

system i + j

Aij (J·mol−1)

1 + 2d 1 + 3a 2 + 3a 1 + 2 + 3ae 1 + 2d 1 + 3a 2 + 3a 1 + 2 + 3ae 1 + 2d 1 + 3a 2 + 3a 1 + 2 + 3ae

171.69 −782.07 44.06

1 + 3b 2 + 3b 1 + 2 + 3be 1 + 3b 2 + 3b 1 + 2 + 3be 1 + 3b 2 + 3b 1 + 2 + 3be

−536.72 −30.51

−154.16 2282.64 2391.50 −78.87 1403.48 1421.65

2685.93 2814.10 1075.06 1184.02

Aji (J·mol−1)

αij

Diethyl Carbonate (3a) −131.00 2778.56 3227.50 195.66 −315.62 691.80

0.2 0.3 0.3

88.58 −727.20 −475.08 Methyl Isobutyl Ketone (3b) 2363.06 2788.31 −830.79 −151.02 −563.05 −467.56

0.3 0.3

ARDTa/%

100·AADy1b

0.056 0.180 0.076 0.398 0.056 0.163 0.134 0.271 0.056 0.169 0.121 0.259

0.115 0.336

0.211 0.065 0.787 0.190 0.089 0.776 0.195 0.085 0.785

0.554 0.116 0.367 0.588 0.116 0.340 0.590

100·AADy2b

0.538 0.599

0.596 0.641

0.569 0.620

0.731 0.425 0.717 0.419 0.724 0.422

0.660 0.608 0.649 0.614 0.649 0.609

a Average relative deviation in temperature. bAverage absolute deviation in vapor phase composition. cMolar liquid volumes of pure components have been estimated with the Rackett equation.14 dReference 7. eTernary estimation from binary parameters. fVolume and surface parameters from DECHEMA.15

D



Article

pure-component vapor pressure, Bij the cross second virial coefficient and

Table 10. Experimental Vapor−Liquid Equilibrium Data for the System 1-Hexene (1) + n-Hexane (2) + Diethyl Carbonate (3a) at 100.0 kPaa: Temperature (T), Mole Fraction of the Liquid Phase (xi), Mole Fraction of the Vapor Phase (yi), and Activity Coefficients (γi) T (K)

x1

x2

y1

y2

γ1

γ2

γ3a

384.03 363.08 350.73 344.27 337.93 339.48 342.50 345.44 348.90 352.46 356.88 361.18 368.72 363.88 357.35 352.13 348.30 345.58 341.35 339.35 340.78 343.22 346.23 349.51 352.92 358.86 352.49 349.49 346.52 343.82 339.83 341.54 344.28 347.04 351.20 347.90 345.10 341.17 342.74 346.14 343.60 342.37

0.043 0.218 0.423 0.634 0.887 0.789 0.673 0.555 0.437 0.346 0.256 0.191 0.102 0.091 0.178 0.265 0.365 0.460 0.624 0.717 0.570 0.475 0.377 0.261 0.172 0.056 0.097 0.184 0.289 0.377 0.535 0.377 0.288 0.196 0.062 0.086 0.197 0.328 0.192 0.056 0.098 0.046

0.040 0.032 0.048 0.048 0.053 0.091 0.086 0.086 0.087 0.088 0.087 0.086 0.090 0.152 0.160 0.179 0.188 0.187 0.199 0.190 0.300 0.293 0.278 0.268 0.262 0.265 0.362 0.358 0.368 0.385 0.391 0.498 0.469 0.459 0.458 0.552 0.553 0.585 0.680 0.678 0.763 0.886

0.179 0.638 0.781 0.861 0.935 0.877 0.845 0.796 0.734 0.672 0.605 0.506 0.334 0.259 0.410 0.508 0.593 0.667 0.740 0.782 0.653 0.601 0.528 0.440 0.333 0.120 0.178 0.302 0.405 0.482 0.598 0.443 0.377 0.271 0.092 0.128 0.254 0.381 0.235 0.082 0.117 0.056

0.192 0.124 0.106 0.073 0.052 0.095 0.106 0.129 0.161 0.194 0.224 0.259 0.337 0.482 0.403 0.360 0.308 0.259 0.219 0.186 0.312 0.346 0.387 0.453 0.530 0.699 0.690 0.589 0.517 0.461 0.382 0.522 0.564 0.642 0.792 0.783 0.683 0.592 0.728 0.849 0.835 0.916

1.190 1.373 1.203 1.062 0.994 1.001 1.034 1.085 1.151 1.206 1.303 1.305 1.335 1.309 1.254 1.201 1.133 1.092 1.010 0.986 0.992 1.020 1.035 1.136 1.187 1.121 1.139 1.107 1.028 1.013 0.996 0.995 1.024 0.999 0.954 1.049 0.985 0.995 1.001 1.085 0.952 1.007

1.662 2.160 1.697 1.400 1.089 1.106 1.194 1.336 1.495 1.616 1.679 1.760 1.822 1.733 1.623 1.488 1.346 1.228 1.103 1.041 1.060 1.121 1.212 1.343 1.465 1.635 1.396 1.308 1.213 1.117 1.024 1.045 1.107 1.190 1.311 1.178 1.110 1.019 1.030 1.093 1.027 1.005

1.062 0.988 1.053 1.322 1.795 1.810 1.392 1.269 1.168 1.092 1.016 1.084 1.041 1.036 1.084 1.109 1.201 1.266 1.663 2.684 1.979 1.519 1.450 1.175 1.097 0.968 1.124 1.232 1.323 1.554 2.067 1.995 1.546 1.437 1.170 1.355 1.553 2.245 1.961 1.533 2.261 2.837

δji = 2Bij − Bjj − Bii

The standard state for the calculation of activity coefficients is the pure component at the pressure and temperature of the solution. Equation 1 is valid at low and moderate pressures when the virial equation of state truncated after the second coefficient is adequate to describe the vapor phase of the pure components and their mixtures, and pure components in liquid state are considered incompressible under consideration over the pressure range. The molar virial coefficients Bii and Bij were estimated by the method of Hayden and O’Connell10 using the molecular parameters suggested by Prausnitz et al.11 The critical properties of all components were taken from DIPPR.12 The pure component vapor pressures were determined previously,4,5,7 and the equation and the parameters to calculate them are listed in Table 7. According to the results, all binary systems present positive deviations from Raoult’s law and do not show any azeotrope. In Figure 2, some little differences among experimental data from this work and those obtained by Rodriguez et al.8 can be observed, particularly at high compositions of diethyl carbonate. This small discrepancy could be the sum of different factors, such as the difference between work pressures (data of ref 8 were determined at 101.3 kPa) and the purity of diethyl carbonate used. Both works use the same commercial diethyl carbonate; however, this compound was purified until 99.98% mass fraction in this work. The thermodynamic consistency of the VLE data, for each binary system, has been verified with the point-to-point Fredenslund test.13 Obtained deviations and the corresponding parameters of the Legendre polynomial required in this test are given in Table 8. As can be appreciated, the consistency criteria (AADy < 0.01) was achieved for the four binary systems. The VLE data for each binary system have been correlated using local composition models (Wilson, NRTL, and UNIQUAC). For the Wilson model, molar liquid volumes of pure components have been estimated with the Rackett equation,14 and for UNIQUAC model, volume and surface parameters were taken from DECHEMA.15 The parameters of these models have been determined minimizing the following objective function (OF):

(γi) were calculated from the following equation9 assuming nonideality of both liquid and vapor phases: xiPi0

+

(3)

where the superscript expt and calc refer to the experimental and calculated points, respectively. Obtained parameters are reported in Table 9, together with the obtained average deviations of the correlation. Analyzing the results given in that table, it can be concluded that the three local composition models are adequate for the description of the VLE of the binary systems, without any significant difference between them. Ternary Systems. VLE data for the ternary system 1-hexene (1) + n-hexane (2) + diethyl carbonate (3a) are reported in Table 10 and Figure 5 while VLE data of the ternary system 1-hexene (1) + n-hexane (2) + methyl isobutyl ketone (3b) are reported in Table 11 and Figure 6. According to these data, the ternary systems do not present any azeotrope. The activity coefficients (γi) were calculated from eq 1, and the molar virial coefficients were estimated as well as for the binary systems. The ternary data were found to be thermodynamically consistent

u(T) = 0.02 K, u(p) = 0.05 kPa, and u(x1) = u(x2) = u(y1) = u(y2) = 0.005.

γiP

⎛ T expt − T calc ⎞ ⎜⎜ i expt i 100 × + |yiexpt − yicalc |⎟⎟ ∑ Ti ⎝ ⎠ i=1 N

OF =

a

ln γi = ln

(2)

(Bii − ViL)(P − Pi0) RT

P ∑ ∑ yyi k (2δji − δjk) (1) RT where T and P are the equilibrium temperature and pressure, ViL is the molar liquid volume of component i, Bii and Bjj are the second virial coefficients of the pure gases, Poi is the +

E



Article

Figure 5. Diagram of VLE for the ternary system 1-hexene (1) + n-hexane (2) + diethyl carbonate (3a) at 100.0 kPa: ●, liquid-phase mole fractions; △, vapor-phase mole fractions.

Table 11. Experimental Vapor−Liquid Equilibrium Data for the System 1-Hexene (1) + n-Hexane (2) + Methyl Isobutyl Ketone (3b) at 100.0 kPaa: Temperature (T), Mole Fraction of Liquid Phase (xi), Mole Fraction of Vapor Phase (yi), and Activity Coefficients (γi) T (K)

x1

x2

y1

y2

γ1

γ2

γ3b

380.48 370.24 363.61 359.36 355.89 356.27 357.59 359.19 361.03 363.31 366.16 369.59 373.73 368.34 365.07 362.75 360.34 358.41 356.34 355.36 355.55 356.82 358.27 359.95 361.99

0.047 0.048 0.049 0.049 0.050 0.102 0.101 0.099 0.099 0.096 0.096 0.099 0.098 0.196 0.199 0.198 0.197 0.203 0.204 0.202 0.299 0.296 0.296 0.295 0.297

0.047 0.242 0.440 0.647 0.901 0.799 0.695 0.591 0.490 0.388 0.290 0.194 0.098 0.100 0.198 0.291 0.400 0.507 0.663 0.755 0.604 0.498 0.397 0.290 0.195

0.150 0.112 0.086 0.069 0.056 0.117 0.126 0.137 0.150 0.167 0.189 0.221 0.255 0.418 0.370 0.328 0.290 0.265 0.234 0.219 0.331 0.356 0.388 0.429 0.478

0.126 0.467 0.656 0.779 0.911 0.822 0.765 0.708 0.646 0.575 0.484 0.366 0.216 0.181 0.317 0.417 0.513 0.588 0.686 0.750 0.609 0.535 0.456 0.369 0.269

1.000 0.927 0.815 0.725 0.635 0.642 0.675 0.714 0.753 0.809 0.856 0.897 0.942 0.881 0.832 0.784 0.740 0.693 0.643 0.621 0.631 0.663 0.696 0.740 0.777

1.002 0.910 0.820 0.737 0.677 0.682 0.704 0.735 0.773 0.821 0.863 0.902 0.952 0.893 0.848 0.805 0.765 0.727 0.685 0.675 0.681 0.701 0.724 0.766 0.789

1.000 1.012 1.073 1.226 1.850 1.674 1.400 1.240 1.146 1.075 1.038 1.017 1.010 1.032 1.050 1.091 1.162 1.282 1.617 2.027 1.743 1.423 1.293 1.173 1.115

365.98

0.284

0.045

0.569

0.078

0.877

0.891

1.033

Table 11. continued T (K)

x1

x2

y1

y2

γ1

γ2

γ3b

361.18

0.394

0.100

0.620

0.136

0.777

0.795

1.108

359.13 357.59

0.401 0.401

0.199 0.303

0.563 0.508

0.244 0.340

0.731 0.686

0.754 0.720

1.190 1.329

356.31

0.403

0.402

0.470

0.422

0.653

0.695

1.510

354.81

0.398

0.550

0.424

0.541

0.620

0.676

1.976

355.05

0.499

0.398

0.540

0.396

0.626

0.681

1.790

356.11

0.497

0.298

0.577

0.312

0.653

0.696

1.491

357.33

0.493

0.204

0.620

0.230

0.685

0.726

1.307

359.47

0.498

0.055

0.717

0.070

0.742

0.775

1.162

356.82

0.608

0.101

0.744

0.111

0.676

0.718

1.334

355.72

0.599

0.203

0.684

0.209

0.650

0.691

1.508

354.36

0.600

0.350

0.625

0.340

0.613

0.678

2.052

354.54

0.700

0.199

0.740

0.196

0.620

0.681

1.861

356.18

0.699

0.052

0.811

0.056

0.652

0.710

1.468

354.29

0.800

0.104

0.835

0.102

0.617

0.683

1.933

353.82

0.899

0.053

0.914

0.051

0.608

0.679

2.191

a

u(T) = 0.02 K, u(p) = 0.05 kPa, and u(x1) = u(x2) = u(y1) = u(y2) = 0.005.

by the Wisniak and Tamir16 modification of the McDermott− Ellis test.17 The test requires that D < Dmax for every experimental point, where the local deviation D between two consecutive experimental data (xia, xib) is given by N

D=

∑ (xia + xib)(ln γia − ln γib) i=1

(4)

and N is the number of components. The maximum deviation Dmax is given by F



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Figure 6. Diagram of VLE for the ternary system 1-hexene (1) + n-hexane (2) + methyl isobutyl ketone (3b) at 100.0 kPa: ●, liquid-phase mole fractions; △, vapor-phase mole fractions.

⎛

N

Dmax =

∑ (xia + xib)⎜⎜ 1

⎝ xia

i=1

N

+

∑ (xia + xib) ΔP i=1 N

+

p

+

1 1 1⎞ + + ⎟⎟Δx yia xib yib ⎠

(nodes and saddles). 1-Hexene is an unstable node; n-hexane is a saddle, and the solvent (diethyl carbonate or methyl isobutyl ketone) is a stable node. So, 1-hexene could be obtained as an overhead product, and any of the two solvents would be the bottom product. This behavior is consistent with the boiling points of the components employed here. In these two cases the residue curve maps give little valuable information. Another useful method is to study the changes in the relative volatility of 1-hexene to n-hexane (α12 = 1.177)7 after adding the solvent. In this sense, Table 12 provides values of mean relative volatilities in the presence of the solvent (αS12) for four different solvents compositions (for x3 = 0.2, 0.4, 0.6, and 0.8). Moreover, the differences between molar fractions of the vapor phase and the liquid phase versus molar fractions of the liquid phase for each ternary system are plotted in Figures 9 and 10, respectively. These representations are made on a solvent-free basis, so the effect of adding solvent can be better appreciated. Data from both Table 12 and Figures 9 and 10 indicate that the two studied solvents show a poor behavior as extractive distillation entrainers because the two values of mean relative volatility in the presence of the solvents are closer to unity than the original solvent-free value. Even further, a reversal in the initial binary mixture volatility is produced for high compositions of the solvents. These results are completely different from the obtained in previous works with cyclohexane and cyclohexene and the same solvents proposed here.4,5 In those works, it can be seen that diethyl carbonate and methyl isobutyl ketone increased the relative volatility of cyclohexane to cyclohexene, and these solvents could be used as entrainers for separating, by extractive distillation, this cyclic paraffin and olefin mixture. However, the effects of these solvents found in the binary system 1-hexene + n-hexane are very similar to the found with 2-pentanol and ethyl butyrate6 and imply the refusal of the two solvents as entrainers in extractive distillation for separating 1-hexene from n-hexane.

N

+ 2 ∑ |ln γb − ln γia|Δx i=1

∑ (xia + xib)Bj{(Ta + Cj)−2 + (Tb + Cj)−2 }ΔT i=1

(5)

where Δx, ΔP and ΔT are the errors in the measurements of these experimental variables, respectively, and were indicated previously. The first and fourth terms in eq 5 are the largest. For each experimental point reported here the value of D was always smaller than the value of Dmax. VLE data for the ternary systems have been estimated by using the Wilson, NRTL, and UNIQUAC models with the binary interaction parameters obtained from the regression of binary data. Table 9 lists the average deviations between experimental and calculated temperatures and vapor phase mole fractions of the components. The three models represent the two ternary data successfully without any significant difference. So, the NRTL model has been chosen as a representative example and has been used for all of the subsequent theoretical calculations. Solvent Effects. To evaluate the role of diethyl carbonate and methyl isobutyl ketone as entrainers in the extractive distillation process, the residue curve maps of the ternary systems have been obtained with the software Aspen properties v7.3, developed by AspenTech. The residue curve map for the system 1-hexene + n-hexane + diethyl carbonate is shown in Figure 7 and that corresponding to the other ternary system 1-hexene + n-hexane + methyl isobutyl ketone in Figure 8. Both maps have the same characteristics: there is one unique distillation region with the three pure component vertices as singular points G



Article

Figure 7. Residue curve map for the ternary system 1-hexene (1) + n-hexane (2) + diethyl carbonate (3a) at 100.0 kPa simulated by Aspen Properties using the NRTL model with the parameters given in Table 9.

Figure 8. Residue curve map for the ternary system 1-hexene (1) + n-hexane (2) + methyl isobutyl ketone (3b) at 100.0 kPa simulated by Aspen Properties using the NRTL model with the parameters given in Table 9.

■

CONCLUSIONS To study the 1-hexene/n-hexane separation by an extractive distillation process, two solvents, diethyl carbonate and methyl isobutyl ketone, have been proposed as possible entrainers. Therefore, consistent VLE data at 100.0 kPa have been determined for the two ternary systems constituted by 1-hexene (1),

n-hexane (2), and one of the proposed solvents (3). Also VLE data of some constituent binary systems have been obtained. According to the results, both solvents decrease the relative volatility of 1-hexene to n-hexane; they even invert this relative volatility for high composition of the solvents, so they cannot be used as entrainers in the proposed separation. These results H



Article

hydrocarbons mixtures can be very different, and it would be very risky to extrapolate results and to recommend the same entrainers for separating different kinds of paraffin and olefin mixtures, even with the same number of carbon atoms.

Table 12. Mean Relative Volatility in the Presence of the Solvent (αS12) Calculated Using the NRTL Model for the System 1-Hexene (1) + n-Hexane (2) + Solvent (3) at 100.0 kPa

■

αS12 solvent

x3 = 0.2

x3 = 0.4

x3 = 0.6

x3 = 0.8

diethyl carbonate methyl isobutyl ketone

1.101 1.118

1.025 1.061

0.959 1.014

0.910 0.981

AUTHOR INFORMATION

Corresponding Author

*Tel.: +34 963544317; fax: +34 963544898. E-mail address: [email protected]. ORCID

Sonia Loras: 0000-0002-3863-2201 Funding

Financial support from the University of Valencia, through project no. UV-INV-AE15-340195, is gratefully acknowledged. J.P.-F. and B.M. were funded by a grant from the Ministerio de Economiá y Competitividad of Spain (BES-2011-04636 6) and from La Universidad del Zulia of Venezuela, respectively. Notes

The authors declare no competing financial interest.

■

REFERENCES

(1) Kuipers, N. J. M.; Wentink, A. E.; de Haan, A. B.; Scholtz, J.; Mulder, H. Functionalized solvents for olefin isomer purification by reactive extractive distillation. Chem. Eng. Res. Des. 2007, 85, 88−99. (2) Marrufo, B.; Sanchotello, M.; Loras, S. Isobaric vapor−liquid equilibria for binary and ternary mixtures with cyclohexane, cyclohexene, and morpholine at 100 kPa. Fluid Phase Equilib. 2010, 296, 178−183. (3) Marrufo, B.; Sanchotello, M.; Loras, S. Isobaric vapor−liquid equilibria for Binary and Ternary Mixtures with Cyclohexane, Cyclohexene, and 2-Methoxyethanol at 100 kPa. J. Chem. Eng. Data 2010, 55, 62−68. (4) Marrufo, B.; Sanchotello, M.; Loras, S. Isobaric Vapor-Liquid Equilibria for Binary and Ternary Mixtures with Cyclohexane, Cyclohexene, and Methyl Isobutyl Ketone at 100 kPa. J. Chem. Eng. Data 2010, 55, 5812−5817. (5) Marrufo, B.; Loras, S.; Lladosa, E. Phase Equilibria Involved in the Extractive Distillation of Cyclohexane + Cyclohexene Using Diethyl Carbonate as an Entrainer. J. Chem. Eng. Data 2011, 56, 4790−4796. (6) Marrufo, B.; Rigby, B.; Pla-Franco, J.; Loras, S. Solvent Effects on Vapor−Liquid Equilibria of the Binary System 1-Hexene + n-Hexane. J. Chem. Eng. Data 2012, 57, 3721−3729. (7) Marrufo, B.; Aucejo, A.; Sanchotello, M.; Loras, S. Isobaric vapor− liquid equilibrium for binary mixtures of 1-hexene + n-hexane and cyclohexane + cyclohexene at 30, 60 and 101.3 kPa. Fluid Phase Equilib. 2009, 279, 11−16. (8) Rodriguez, A.; Canosa, J.; Dominguez, A.; Tojo, J. Isobaric VaporLiquid Equilibria of Diethyl Carbonate with Four Alkanes at 101.3 kPa. J. Chem. Eng. Data 2002, 47, 1098−1102. (9) Van Ness, H. C.; Abbott, M. M. Classical Thermodynamics of Nonelectrolyte Solutions; McGraw-Hill: New York, 1982. (10) Hayden, J.; O’Connell, J. A Generalized Method for Predicting Second Virial Coefficients. Ind. Eng. Chem. Process Des. Dev. 1975, 14, 209−216. (11) Prausnitz, J.; Anderson, T.; Grens, E.; Eckert, C.; Hsieh, R.; O’Connell, J. Computer Calculation for Multicomponent Vapor-Liquid and Liquid-Liquid Equilibria; Prentice Hall: Englewood Cliffs, NJ, 1980. (12) Daubert, T. E.; Danner, R. P. Physical and Thermodynamic Properties of Pure Chemicals. Data Compilation; Taylor & Francis: Bristol, PA, 1989. (13) Fredenslund, A.; Gmehling, J.; Rasmussen, P. Vapor-Liquid Equilibria Using UNIFAC. A Group Contribution Method; Elsevier: Amsterdam, 1977. (14) Rackett, H. G. Equation of State for Saturated Liquids. J. Chem. Eng. Data 1970, 15, 514−517.

Figure 9. VLE data plotted on a solvent-free basis for the system 1-hexene (1) + n-hexane (2) + diethyl carbonate (3a) at 100.0 kPa. Continuous line7 for x3a = 0.00: Long dashed line for x3a = 0.80, short dashed line for x3a = 0.60, dash−dotted line for x3a = 0.40, and dotted line for x3a = 0.20 calculated using the NRTL model with the parameters given in Table 9.

Figure 10. VLE data plotted on a solvent-free basis for the system 1-hexene (1) + n-hexane (2) + methyl isobutyl ketone (3b) at 100.0 kPa. Continuous line7 for x3b = 0.00: Long dashed line for x3b = 0.80, short dashed line for x3b = 0.60, dash−dotted line for x3b= 0.40, and dotted line for x3b = 0.20 calculated using the NRTL model with the parameters given in Table 8.

are completely different from the obtained in the mixture of cyclohexane and cyclohexene with the same solvents.4,5 So, in the separation of paraffins and olefins, it can be concluded that the solvent effects on vapor−liquid equilibrium of linear and cyclic I



Article

(15) Gmehling, J.; Onken, U. Vapor-Liquid Equilibrium Data Collection; DECHEMA: Frankfurt, 1977. (16) Wisniak, J.; Tamir, A. Vapor-Liquid Equilibria in the Ternary System Water-Formic Acid-Acetic Acid and Water-Acetic AcidPropionic Acid. J. Chem. Eng. Data 1977, 22, 253−260. (17) McDermott, C.; Ellis, S. R. M. A Multicomponent Consistency Test. Chem. Eng. Sci. 1965, 20, 293−296. (18) NIST Standard Reference Database 85, NIST/TRC Table Database, WinTable; NIST: Gaithersburg, MD, 2004.

J


Evaluation of Diethyl Carbonate and Methyl Isobutyl Ketone as

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