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Feb 16, 2016 - In this study, a substitutive entrainer is found for the azeotropic process of water and isopropyl alcohol (IPA). Liquid–liquid equil...
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Liquid−Liquid Equilibrium Data for the Ternary Systems of Water, Isopropyl Alcohol, and Selected Entrainers Hyeung Chul Choi, Jae Sun Shin, Faraz Qasim, and Sang Jin Park* Dongguk University, 30, Pildong-ro 1-gil, Jung-gu, Seoul 100-715, Republic of Korea ABSTRACT: In this study, a substitutive entrainer is found for the azeotropic process of water and isopropyl alcohol (IPA). Liquid−liquid equilibrium (LLE) data are measured for the ternary systems of water−IPA−benzene, water−IPA−cyclohexane, and water− IPA−hexane at three different temperature values: 303, 313, and 323 K. The liquid−liquid equilibrium data are developed via an experimental setup equipped with equilibrium cell, magnetic stirrer, and gas chromatography units. Equilibrium compositions for the water−IPA system are found by using three different entrainers: benzene, cyclohexane, and hexane. Parameters calculated by nonrandom two-liquid (NRTL) and universal quasichemical (UNIQUAC) thermodynamic models are compared with the data obtained by experiments, and the comparison shows a good correlation between thermodynamic models and the experimental data.



INTRODUCTION Entrainers have immense importance for the separation of the azeotropic mixtures and have been widely exploited for the recovery of many useful components in industries. Importance of entrainers can be justified by previous literature.1−4 For designing a separation process, the liquid−liquid equilibrium data are essential for specifying design conditions. The phase equilibrium data for the separation processes of water−IPA− entrainer are rare in past literature. Hence, this study is carried out to make LLE data available for the separation of IPA from water by using entrainers. IPA is widely used in medicine, electronics, and paint industries as a solvent and raw material. IPA is also adopted as a cleaning agent in production of semiconductors and several chemicals in process technology industires. However, an azeotrope exits at 87.8 wt % and azeotropic boiling point of 80.3 °C in the water−IPA system and the separation of IPA becomes tougher as it needs infinite number of trays due to presence of azeotropic composition. Hence, azeotropic distillation is suggested as a favorable option to increase the purity of IPA from 87.8% to 99.9%.5,6 For designing the separation processes and to determine theoretical number of stages, liquid−liquid equilibrium (LLE) data are required, which are, unfortunately, rare in the past literature for a wide range of temperatures for the water−IPA− entrainer system. In a past few years, the use of benzene as an entrainer is diminishing with time as benzene is being considered as environmentally hazardous entrainer. Other environment friendly entrainers must be analyzed and utilized in the separation processes.7−9 Hence, an intensive research is being done to find beneficial entrainers to replace benzene. The past literature also provides the phase equilibria of the studied systems, i.e., water−cyclohexane−IPA,10−16 water−hexane−IPA,17,18 and water−benzene−IPA.19−30 In this work, phase equilibrium for © XXXX American Chemical Society

the water−PA system is developed by using three entrainers, benzene, cyclohexane, and hexane. The developed data for three entrainers can be used to find the better substitutive entrainer in future on environmental and economic basis for the separation of IPA from water. In this study, NRTL (nonrandom two-liquid) and UNIQUAC (UNIversal QUAsi Chemical) liquid activity coefficient models are used to correlate the experimentally found LLE data for the water−IPA system. The exact liquid activity coefficient parameters are found, and a comparison of experimental data with thermodynamic models is done.



EXPERIMENTAL APPARATUS AND METHOD Experiment is carried out by using commercially available chemicals which are bought from Sigma-Aldrich. First, different drying reagents are used to fractionally distill the solvents. The purities of all chemicals are then tested by gas chromatography which shows that purity of all chemicals is above 99.5% and no further impurities could be found chromatographically. Hence, the chemicals are used without further purification. Furthermore, the density of the solvents is found using a vibrating-tube densimeter (Anton Paar) which has a standard uncertainty up to 10 kg·m−3 and temperature range of 263−423 K with a standard uncertainty of 0.1 K. The density measurements are done under atmospheric pressure, and the standard uncertainty in pressure is 1 kPa. The physical data for the chemicals used in this work are shown in Table 1 which portrays the density, purity, molecular weight, and boiling point of all chemicals. Distilled water is used throughout this study. Figure 1 shows the self-designed experimental setup for the process which consists of temperature Received: July 2, 2015 Accepted: February 8, 2016

A

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Table 1. Physical Data Information for Chemicals Utilized chemical name

source

density (g/mL at25 °C)

IPA benzene cyclohexane hexane water

Aldrich Aldrich Aldrich Aldrich

0.798 0.874 0.779 0.659

initial puritya (mole fraction)

analysis methodb

0.995 0.998 0.999 0.999 distilled water used

GC GC GC GC

MW

bp (°C) (source = Aldrich)

61.09 78.11 84.16 86.18

82.4 °C 80 °C 80.7 °C 69 °C

Initial purity mentioned by the supplier. bGas chromatography, uncertainty in density by Anton Paar = 10 kg·m−3, standard uncertainty in temperature (density measurement by Anton Paar) = 0.1 K, and standard uncertainty in pressure u(P) = 1 kPa. a

Table 2. Experimental Tie-Line Data for the IPA (1) + Entrainer (2) + Water (3) System at Temperature T = 303 K and Pressure P = 101.325 kPa by Using Hexane as an Entrainera aqueous phase

Figure 1. Experimental setup for liquid−liquid equilibria.

indicator, magnetic stirrer, injection loop, gas chromatography, vacuum pump, and equilibrium cell. Equilibrium cell operation has been well studied and applied in previous literature.31−38 The volume of equilibrium cell is 300 cm3. Vacuum state is generated in equilibrium cell with the help of a vacuum pump and alcohol is added. A magnetic stirrer is used for continuous and sufficient stirring of the liquid inside the equilibrium cell. The vigorous mixing is done for more than 8 h after which the mixture is allowed to get intact for 3 h. The settling time is provided to make sure that the equilibrium state is achieved. As a result, mixture splits into two phases after about 3 h making organic and aqueous phases. An injection tube of 1/8 in. is used to take sample, and it is analyzed by gas chromatography apparatus. The same experimental method is used to repeat the process for different operating conditions of temperature. Gas chromatography equipment used for analysis is Hewlett-Packard, 5890 ser. II consisting of column HP-FFAP (cross-linked FFAP) (25 m × 0.32 mm × 0.52 μm) while GC analyzer consists of a detector TCD (thermal conductivity detector). GC analysis is done to measure the aqueous and organic phases for LLE data, and the standard uncertainties for composition in mole fraction are estimated to be 0.02, while the standard uncertainty in temperature measurement is found out to be 0.01 K. Average values of both phases are taken into account after measuring each sample for three times. The injection unit, which takes sample, is connected with carrier gas line which has 99.99% pure carrier gas and vaporizes at the temperature of 423 K. Detector, column, and injection port have temperature values 523, 423, and 473 K, respectively, while oven is operated at initial and final temperatures of 323 and 383 K, respectively, with the rise rate of 20 K·min−1.

organic phase

x11

x21

x31

x12

x22

x32

0.006 0.024 0.109 0.188 0.273 0.343 0.357 0.420 0.420 0.412

0.991 0.969 0.873 0.768 0.644 0.510 0.471 0.112 0.155 0.309

0.003 0.008 0.018 0.044 0.083 0.147 0.172 0.468 0.425 0.279

0.016 0.059 0.114 0.185 0.285 0.357 0.390 0.396 0.401 0.423

0.004 0.000 0.001 0.003 0.013 0.042 0.072 0.374 0.346 0.204

0.980 0.941 0.885 0.812 0.702 0.601 0.538 0.230 0.253 0.373

a Standard uncertainties u; temperature = u(T) = 0.01 K, composition = u(x) = 0.02, pressure u(p) = 1 kPa, (x11, x21, x31, x12, x22, x32) = xij = composition of component i in j phase while j being water in aqueous phase and entrainer in organic phase.

Table 3. Experimental Tie-Line Data for the IPA (1) + Entrainer (2) + Water (3) System at Temperature T = 313 K and Pressure P = 101.325 kPa by Using Hexane as an Entrainera aqueous phase

organic phase

x11

x21

x31

x12

x22

x32

0.006 0.020 0.120 0.219 0.285 0.338 0.369 0.388 0.397 0.416

0.991 0.972 0.854 0.726 0.613 0.499 0.437 0.389 0.337 0.282

0.003 0.008 0.026 0.055 0.102 0.163 0.194 0.223 0.266 0.302

0.015 0.058 0.142 0.226 0.326 0.375 0.405 0.420 0.417 0.423

0.014 0.010 0.012 0.024 0.029 0.052 0.069 0.095 0.129 0.177

0.970 0.932 0.846 0.750 0.646 0.574 0.526 0.485 0.454 0.400

a

Standard uncertainties u; temperature = u(T) = 0.01 K, composition = u(x) = 0.02, pressure u(p) = 1 kPa, (x11, x21, x31, x12, x22, x32) = xij = composition of component i in j phase while j being water in aqueous phase and entrainer in organic phase.

given in Tables 2−10, are u(T) = 0.01 K and u(x) = 0.02, respectively. The two phase region shows a decreasing trend with increasing temperature, and it can be seen from Figures 2−4 that all entrainer systems show same trend regarding two-phase region for the water−IPA system. The system water−IPA with cyclohexane as an entrainer has been studied previously by various researchers. Washburn10,11 developed the LLE data for the water−cyclohexane−IPA system at 288.15, 298.15, and 308.15 K with the reported estimated error of ±0.05 °C in temperature. The data show the equilibrium



RESULTS AND DISCUSSION Tables 2 to 10 depict the tie line data and Figures 2 to 4 demystify tie-line plots for water−entrainer−IPA system using benzene, cyclohexane, and hexane as entrainers. The tie lines are drawn by using experimental data with three entrainers at different values of temperature as shown in Tables 2−10. The standard uncertainties for temperature and composition in LLE data, B

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Table 4. Experimental Tie-Line Data for the IPA (1) + Entrainer (2) + Water (3) System at Temperature T = 323 K and Pressure P = 101.325 kPa by Using Hexane as an Entrainera aqueous phase

Table 6. Experimental Tie-Line Data for the IPA (1) + Entrainer (2) + Water (3) System at Temperature T = 313 K and Pressure P = 101.325 kPa by Using Cyclohexane as an Entrainera

organic phase

x11

x21

x31

x12

x22

x32

0.006 0.085 0.171 0.249 0.305 0.327 0.350 0.386 0.403 0.404

0.991 0.895 0.797 0.682 0.576 0.532 0.459 0.367 0.306 0.286

0.003 0.020 0.032 0.069 0.119 0.141 0.191 0.247 0.291 0.310

0.035 0.107 0.186 0.270 0.322 0.357 0.383 0.404 0.411 0.412

0.008 0.014 0.029 0.024 0.039 0.069 0.071 0.094 0.145 0.187

0.956 0.880 0.786 0.707 0.639 0.575 0.547 0.502 0.444 0.401

aqueous phase

a Standard uncertainties u; temperature = u(T) = 0.01 K, composition = u(x) = 0.02, pressure u(p) = 1 kPa, (x11, x21, x31, x12, x22, x32) = xij = composition of component i in j phase while j being water in aqueous phase and entrainer in organic phase.

aqueous phase x31

x12

x22

x32

0.394 0.386 0.363 0.337 0.319 0.261 0.179 0.154 0.102 0.016

0.230 0.316 0.406 0.486 0.571 0.661 0.807 0.840 0.891 0.979

0.376 0.298 0.232 0.177 0.110 0.078 0.015 0.006 0.007 0.006

0.375 0.358 0.336 0.312 0.280 0.194 0.122 0.087 0.041 0.004

0.126 0.092 0.056 0.046 0.032 0.014 0.013 0.009 0.002 0.001

0.499 0.550 0.608 0.642 0.688 0.793 0.865 0.904 0.957 0.995

x21

x31

x12

x22

x32

0.001 0.006 0.008 0.009 0.029 0.036 0.067 0.085 0.115 0.159

0.995 0.964 0.912 0.850 0.769 0.674 0.607 0.566 0.519 0.452

0.015 0.116 0.144 0.177 0.253 0.320 0.348 0.379 0.391 0.395

0.969 0.882 0.831 0.799 0.676 0.557 0.461 0.397 0.327 0.249

0.016 0.002 0.025 0.025 0.071 0.123 0.191 0.224 0.282 0.356

Table 7. Experimental Tie-Line Data for the IPA (1) + Entrainer (2) + Water (3) System at Temperature T = 323 K and Pressure P = 101.325 kPa by Using Cyclohexane as an Entrainera

organic phase

x21

x11 0.004 0.031 0.080 0.141 0.203 0.290 0.326 0.349 0.366 0.389

a Standard uncertainties u; temperature = u(T) = 0.01 K, composition = u(x) = 0.02, pressure u(p) = 1 kPa, (x11, x21, x31, x12, x22, x32) = xij = composition of component i in j phase while j being water in aqueous phase and entrainer in organic phase.

Table 5. Experimental Tie-Line Data for the IPA (1) + Entrainer (2) + Water (3) System at Temperature T = 303 K and Pressure P = 101.325 kPa by Using Cyclohexane as an Entrainera x11

organic phase

aqueous phase

a

Standard uncertainties u; temperature = u(T) = 0.01 K, composition = u(x) = 0.02, pressure u(p) = 1 kPa, (x11, x21, x31, x12, x22, x32) = xij = composition of component i in j phase while j being water in aqueous phase and entrainer in organic phase.

organic phase

x11

x21

x31

x12

x22

x32

0.005 0.031 0.070 0.116 0.190 0.261 0.303 0.347 0.371 0.376

0.001 0.006 0.008 0.016 0.040 0.049 0.066 0.074 0.119 0.148

0.995 0.963 0.922 0.869 0.770 0.690 0.631 0.579 0.510 0.476

0.015 0.080 0.151 0.190 0.237 0.283 0.332 0.367 0.378 0.385

0.959 0.897 0.823 0.787 0.703 0.624 0.470 0.382 0.297 0.224

0.026 0.023 0.026 0.024 0.060 0.093 0.198 0.251 0.325 0.391

a

Standard uncertainties u; temperature = u(T) = 0.01 K, composition = u(x) = 0.02, pressure u(p) = 1 kPa, (x11, x21, x31, x12, x22, x32) = xij = composition of component i in j phase while j being water in aqueous phase and entrainer in organic phase.

phase difference by maximum mole fraction of 0.07 in hydrocarbon and water rich phases. Nikurashina et al.,12 Letcher et al.,13 and Plachov et al.14 also studied this ternary system at 298.2 K, and the compositions along the saturation curves exhibited the small difference of mole fractions with some exceptions of large differences in the study by Verhoeye.15 Another studies for this ternary system were carried out by Skrzecz and Washburn16 who found the phase equilibrium at 298 K. In our study, the LLE data is developed at 303, 313, and 323 K, and the two-phase region is showing the decreasing behavior with the increase in temperature. The same trend is observed while comparing to the previous literature. The two phase regions is increased at 298 K, and the equilibrium phases differ by maximum of 0.03 mole fraction at 298 K. The reported data in our study is consistent too with all the data sets. The ternary system water−hexane−IPA is also studied previously by Vorobeva etal.17 and Morozov et al.18 who found the phase equilibrium data at 298.2 and 331.2 K, respectively. The miscibility gap and the direction of the tie lines match to the

Table 8. Experimental Tie-Line Data for the IPA (1) + Entrainer (2) + Water (3) System at Temperature T = 303 K and Pressure P = 101.325 kPa by Using Benzene as an Entrainera aqueous phase

organic phase

x11

x21

x31

x12

x22

x32

0.983 0.968 0.950 0.933 0.922 0.906 0.892 0.874

0.002 0.003 0.001 0.002 0.003 0.004 0.006 0.008

0.015 0.029 0.049 0.065 0.076 0.090 0.102 0.117

0.002 0.005 0.014 0.032 0.074 0.154 0.259 0.286

0.992 0.973 0.920 0.838 0.706 0.538 0.384 0.309

0.005 0.022 0.066 0.130 0.219 0.308 0.358 0.405

a

Standard uncertainties u; temperature = u(T) = 0.01 K, composition = u(x) = 0.02, pressure u(p) = 1 kPa, (x11, x21, x31, x12, x22, x32) = xij = composition of component i in j phase while j being water in aqueous phase and entrainer in organic phase. C

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data presented in our work. Though the temperature used in previous work does not match to the one used in our study, the two-phase region exhibits the same behavior, and the experimental data agrees well with the predicted one. The ternary system of water, IPA, and benzene is studied also extensively in past literature,19−30 and the phase equilibria are reported for different temperatures ranging from 292 to 343 K. All ternary systems studied in the present work are compared to the past literature published, and the comparisons are shown graphically in Figures 5 to 7 which show that the tie lines in present study and the previous literature exhibit a good agreement. Furthermore, root-mean-square deviations and average absolute deviations, which are rare in past literature for specified temperature values, are found in the present study for all entrainers to find out the most effective entrainer for the separation of IPA and water. NRTL Model. Liquid activity coefficient moels like NRTL (nonrandom two liquid) and UNIQUAC (UNIversal QUAsi Chemical) are used for prediction of LLE data for system of water IPA by using three entrainers. The binary interaction parameters are calculated by using the experimental data and LLE data are found by regression. In 1968, Renon and Prausnitz39−41 proposed a model named as NRTL which is vastly used for prediction and correlation of LLE data. The NRTL model expression is following:

Table 9. Experimental Tie-Line Data for the IPA (1) + Entrainer (2) + Water (3) System at Temperature T = 313 K and Pressure P = 101.325 kPa by Using Benzene as an Entrainera aqueous phase

organic phase

x11

x21

x31

x12

x22

x32

0.983 0.964 0.938 0.915 0.894 0.875 0.849 0.828

0.003 0.007 0.013 0.019 0.026 0.025 0.029 0.028

0.015 0.029 0.049 0.066 0.080 0.100 0.122 0.144

0.002 0.016 0.021 0.042 0.112 0.150 0.264 0.311

0.993 0.962 0.913 0.830 0.660 0.560 0.388 0.319

0.005 0.022 0.067 0.128 0.228 0.290 0.348 0.370

a

Standard uncertainties u; temperature = u(T) = 0.01 K, composition = u(x) = 0.02, pressure u(p) = 1 kPa, (x11, x21, x31, x12, x22, x32) = xij = composition of component i in j phase while j being water in aqueous phase and entrainer in organic phase.

Table 10. Experimental Tie-Line Data for the IPA (1) + Entrainer (2) + Water (3) System at Temperature T = 323 K and Pressure P = 101.325 kPa by Using Benzene as an Entrainera aqueous phase

organic phase

x11

x21

x31

x12

x22

x32

0.980 0.953 0.929 0.893 0.871 0.838 0.818

0.015 0.024 0.033 0.037 0.038 0.038 0.039

0.005 0.023 0.038 0.070 0.091 0.124 0.144

0.005 0.022 0.064 0.115 0.173 0.250 0.319

0.990 0.944 0.823 0.648 0.539 0.411 0.299

0.005 0.034 0.113 0.237 0.288 0.342 0.382

ln γi =

∑j τjiGjixj ∑k Gkixk

+

∑ j

⎡ ∑ xτ G ⎤ ⎢τij − l l lj lj ⎥ ∑k Gkjxk ⎥⎦ ∑k Gkjxk ⎢⎣ xjGij

Gij = exp[− (αij + βijT )τij]

a

Standard uncertainties u; temperature = u(T) = 0.01 K, composition = u(x) = 0.02, pressure u(p) = 1 kPa, (x11, x21, x31, x12, x22, x32) = xij = composition of component i in j phase while j being water in aqueous phase and entrainer in organic phase.

τij = τji = 0

τij =

(1)

gij − gii RT

Gii = Gjj = 1

where τij, αij, and Gij = parameters of NRTL model; i, j = component numbers. Binary interaction parameters for

Figure 2. Equilibrium compositions (mole fraction) of the water−cyclohexane−IPA system. D

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Figure 3. Equilibrium compositions (mole fraction) of the water−hexane−IPA system.

Figure 4. Equilibrium compositions (mole fraction) of the water−benzene−IPA system.

being used for a large number of systems. UNIQUAC model expression is following:

water−IPA system using three entrainers, i.e., cyclohexane, hexane, and benzene are shown in Table 11. Values for αij are fixed at 0.1 or 0.2, and the other parameters Bi,j, Bj,I are calculated by NRTL. UNIQUAC Model. Abrams and Prausnitz put forward UNIQUAC (universal quasichemical) model42−45 which has immense importance for correlation of LLE data and currently E

ln γi = (ln γi)C + (ln γi)R

(2)

⎡ϕ⎤ Z ⎡ϕ⎤ n θ (ln γi)C = ln⎢ i ⎥ + qi ln i + Li − ⎢ i ⎥ ∑ 1j xj 2 ϕi ⎣ xi ⎦ ⎣ xi ⎦ j = 1

(3)

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Figure 5. Experimental tie lines data (compositions in mole fraction) for the water−hexane−IPA system in present study vs ref 17 (Vorobeva et al.) and 18 (Morozov et al.).

Figure 6. Experimental tie lines data (compositions in mole fraction) for the water−cyclohexane−IPA system in present study vs ref 10 (Washburn et al. 1940) and ref 11 (Washburn et al. 1942). n n ⎡ ⎤ ϕτ ⎢ n i ij ⎥ (ln γi)R = i(1 − ln ∑ θτ j ji) − qi ∑ ⎢∑ θ τ ⎥ j=1 j = 1 ⎣ k = 1 k kj ⎦

1j =

Z (ri − qi) − (ri − 1) 2

Z = 10

i i n ∑ j = 1 qjxj

ri =

Vwi 15.17

(4)

τii = τjj = 1 F

qx

θi =

ϕi =

qi =

rx i i n ∑ j = 1 rjxj

⎛ Uji − Uii ⎞ τji = exp⎜ − ⎟ RT ⎠ ⎝

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Figure 7. Experimental tie-line data (compositions in mole fraction) for the water−benzene−IPA system in present study vs ref 26 (Nikurashina and Sinegubova).

Table 11. Parameters Calculated by NRTL and UNIQUAC (Water (1) + IPA (2) + Entrainer (3))a model entrainer benzene

hexane

cyclohexane

a

NRTL

UNIQUAC

i

j

Bi,j

Bj,i

αi,j

Ai,j

Aj,i

water water IPA water water IPA water water IPA

IPA benzene benzene IPA hexane hexane IPA cyclohexane cyclohexane

2489.18 1494.51 −1.104 1758.00 1903.98 395.12 2458.57 1408.91 −1108.38

−639.21 1284.61 −1536.37 −492.96 66.39 −566.57 2722.19 997.46 −1024.40

0.2 0.1 0.2 0.2 0.1 0.1 0.2 0.2 0.2

589.54 1966.22 −580.28 776.22 2364.93 −21.43 846.697 1656.056 −122.699

419.136 −95.90 16.134 −129.028 −385.042 401.276 833.073 577.647 95.05

αi,j, Ai,j, Aj,i, Bi,j, Bi,j = binary interaction parameters; i, j = component numbers.

where qi = area parameter of i component; ri = volume parameter of i component; uij = parameter for interaction between components i and j; Z = coordinate number; γRi = combinatorial part of activity coefficient for component i; γCi = residual part of activity coefficient of component “i”; ϕi = area fraction of component “i”; and θi = volume fraction of component “i”. Table 11 enlists parameters calculated by the UNIQUAC model. Regression of Parameters. In this study, liquid activity coefficients are calculated with NRTL (nonrandom two liquid) and UNIQUAC (UNIversal QUAsi Chemical) thermodynamic models, and the data are compared to find the most effective model. Binary interaction parameters are found by regression of data obtained by experimental procedures and the LLE data are predicted with NRTL and UNIQUAC models. Regression of experimental data is run for calculating LLE data and then the predicted LLE data are compared with experimental data. The results of correlation show that the predicted data agree well with the experimental data which give the reliability to analyze different models for prediction of LLE data. The comparison of experimental data for cyclohexane with predicted data from NRTL and UNIQUAC models is explored in Figure 5.

The experimental data are displayed with dots, while the red and blue solid lines show the calculated data with NRTL and UNIQUAC models, respectively. An objective function defined for regression and root-mean-square deviation (RMSD) can be expressed as follows: 2

3

N

cal 2 OF = min ∑ ∑ ∑ [xjexp , k (i) − x j , k (i)]

(5)

k=1 j=1 i=1 2

RMSD = 100 ×

3

N

cal 2 ∑k = 1 ∑ j = 1 ∑i = 1 [xjexp , k (i) − x j , k (i)]

6N (6)

where xexp shows the experimental mole fractions, xcal shows calculated mole fractions, N is number of points or tie lines in data, while j and k depict the no. of components and phases, respectively, present in the data. Table 11 enlists the parameters calculated by NRTL and UNIQUAC models by using three entrainers: benzene, hexane, and cyclohexane. The predicted LLE data are compared with experimental data to observe the deviations. A comparison of G

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Figure 8. Comparison of experimental LLE data to data calculated by NRTL and UNIQUAC models for the water−cyclohexane−IPA system at 303 K.

model would be useful for the prediction of LLE data for water−IPA−entrainer systems. The calculated thermodynamic parameters and the experimental LLE data found in this study would be useful in the selection of the best solvent and simulation of IPA−water separation. To separate IPA from water, cyclohexane comes out as a promising entrainer on the basis of minimum root-mean-square deviation of 0.00019 for NRTL among all entrainers, and it can be used as a substitutive entrainer for IPA−water system.

phase equilibrium for cyclohexane at 303 K with experimental and predicted LLE data using NRTL and UNIQUAC models is portrayed in Figure 8. It is noteworthy that the predicted data show almost same behavior with minimum deviations. Hence, the predicted data correlate well by using thermodynamic models. Regarding a comparison between NRTL and UNIQUAC models, it is concluded that NRTL model shows the best correlation in comparison with UNIQUAC. The average absolute deviation and root-mean-square deviation values for all entrainers are shown in Table 12. It can be observed from the table that cyclohexane seems



Table 12. AAD and RMSD Values for Entainers Useda entrainer cyclohexane hexane benzene

AAD RMSD AAD RMSD AAD RMSD

NRTL

UNIQUAC

0.00029 0.00019 0.00340 0.00165 0.00280 0.00180

0.21340 0.18191 0.51860 0.26235 0.12548 0.08103

AUTHOR INFORMATION

Corresponding Author

*Tel.: +82-2-2260-3367. E-mail: [email protected]. Author Contributions

H.C, J.S.S., F.Q., and S.J.P. contributed equally. Funding

The work done by authors is financially supported by Dongguk University, Seoul, Korea.

a

Notes

AAD = average absolute deviation; RMSD = root-mean-square deviation.

The authors declare no competing financial interest.



to be a promising entrainer because of its minimum root-meansquare deviation of 0.00019 with NRTL among all the entrainers. Hence, Figure 8 shows the comparison of experimental and predicted data for the best entrainer system, water−IPA− cyclohexane. Its average absolute deviation comes out 0.00029 which also seems effective compared to other entrainers. Furthermore, NRTL shows good results than UNIQUAC on the basis of minimum deviations, and it can be concluded that NRTL model will be the most effective to use in simulation of IPA and water separation.

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CONCLUSION In this work, LLE data for the water−IPA system at temperatures 303, 313, and 323 K have been experimentally developed successfully. The correlation of experimental data to NRTL and UNIQUAC has been probed, and it is concluded that NRTL model correlates better than UNIQUAC. Hence, the NRTL H

DOI: 10.1021/acs.jced.5b00542 J. Chem. Eng. Data XXXX, XXX, XXX−XXX

Journal of Chemical & Engineering Data

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