Thiophene + Cyclohexane

Article pubs.acs.org/jced

Cite This: J. Chem. Eng. Data XXXX, XXX, XXX−XXX

Liquid−Liquid Equilibria for Benzene/Thiophene + Cyclohexane/ Hexadecane + Deep Eutectic Solvents: Data and Correlation Hemayat Shekaari,* Mohammed Taghi Zafarani-Moattar, and Behrouz Mohammadi Department of Physical Chemistry, University of Tabriz, Tabriz 5166616471, Iran

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S Supporting Information *

ABSTRACT: The experimental liquid−liquid equilibria (LLE) for several systems containing benzene or thiophene + cyclohexane or hexadecane + choline chloride-based deep eutectic solvents (DESs) including mono-, di-, and triethanolamines and mono-, di-, and triethylene glycols were measured at T = 298.15 to 308.15 K and atmospheric pressure. The distribution coefficients (β) and selectivities (S) were calculated to evaluate the efficiency of the studied solvents for aromatics (benzene or thiophene) extraction from nonaromatic phases. Generally, the selectivity values decrease with increasing of the temperature for our studied DESs. The Othmer−Tobias equation was used to ensure the consistency of the obtained LLE data. The nonrandom two-liquid (NRTL) and universal quasi-chemical (UNIQUAC) models were used to correlate the experimental LLE data. The Hansen solubility parameters confirm the performance of the studied DESs for benzene and thiophene extraction. The measured LLE data in this study shows better performance of aromatics extraction by the studied DESs from hexadecane-including systems.

1. INTRODUCTION

In the past decade, deep eutectic solvents (DESs) have received noticeable attention17−21 in liquid−liquid extraction of aromatics from nonaromatic phases. DESs show negligible vapor pressure at the ambient condition.22 In addition, DESs could be regenerated by flash distillation. Deep eutectic solvents such as green solvents can be used in separation processes as a good replacement for the most commonly used volatile, flammable, and toxic organic solvents such as N-formylmorpholine (NFM) and sulfolane in Uhde/Formex and UOP/Shell processes, respectively. In the recent years, researchers used DESs as solvents for liquid−liquid extraction. For additional information, the recently used DESs2−4,23−33 are summarized in Table 1. Sander et al. used choline chloride:glycerol (ChCl:Gly) and choline chloride:urea (ChCl:Ur) at a 1:2 mole ratio30 for their study. They found that ChCl:Gly had a better performance for the pyridine extraction from n-hexane. Hadj-Kali et al. used DESs for benzene extraction from cyclohexane at ambient pressure and temperature.32 They found that the distribution coefficient and selectivity showed that tetrabutylammonium bromide (TBABr):sulfolane (1:7), tetrabutylammonium bromide (TBABr):triethylene glycol (1:4), methyltriphenylphosphonium bromide (MTPPBr):triethylene glycol (1:4), and choline chloride:triethylene glycol (1:4) had good performances in benzene extraction from cyclohexane via liquid−liquid extrac-

The increasing demand of green solvents has led to development of novel generation of solvents, namely, deep eutectic solvents (DESs). DESs generally are mixtures of ammonium salts as hydrogen bond acceptors (HBAs) in combination with hydrogen bond donors (HBDs),1 which show lower freezing points than those of their pure constituents.1 Also, DESs show special properties such as biodegradability, nonflammability, chemical and thermal stability, negligible vapor pressure, and reasonable cost.2 The above mentioned features make them proper for their applications as solvents, catalysts, reaction media, and additives.3 The separation process for azeotropic mixtures is one of the challenging issues in the industries. Several alternatives have been introduced for their separation in the literature.4−6 In general, the separation technologies may be divided into three branches: (1) enhanced distillation techniques,4 (2) membrane processes,5 and (3) liquid−liquid extraction (LLE).6 Instead of LLE that works based on solubility differences, enhanced distillation techniques work on high relative volatility differences. Since the modification of the relative volatility is sometimes complicated, liquid extraction is a great alternative for the separation of azeotropic mixtures.6 Totally, some key criteria for a proper solvent for extraction are selectivity,7 capacity in solvation of solutes,7 a high boiling point and low volatility,8 extraction performance,9 reasonable cost,10 low toxicity,11 stability,12 noncorrosive effects,13,14 and low viscosity.15,16 © XXXX American Chemical Society

Received: April 11, 2019 Accepted: August 8, 2019

A

DOI: 10.1021/acs.jced.9b00313 J. Chem. Eng. Data XXXX, XXX, XXX−XXX

Journal of Chemical & Engineering Data

Article

Table 1. Summary of Used DESs for Aromatic/Nonaromatic Separation HBA

HBD

methyltriphenylphosphonium bromide (MTPB) methyltriphenylphosphonium bromide (MTPB) methyltriphenylphosphonium iodide (MTPI) choline chloride (ChCl) tetrabutylphosphonium bromide (TBPB) tetrahexylammonium bromide (THAB) tetrabutylammonium bromide (TBAB) tetraethylammonium bromide (TEAB) choline chloride (ChCl) choline chloride (ChCl) choline chloride (ChCl) tetramethylammonium chloride (TMAC) tetraethylammonium chloride (TEAC) tetrabutylammonium chloride (TBAC) tetrahexylammonium chloride (THAC) tetrabutylammonium bromide (TBAB) choline chloride (ChCl)

nonaromatic

ref

ethylene glycol ethylene glycol/sulfolane ethylene glycol/sulfolane lactic acid/glycerol levonic acid ethylene glycol/glycerol ethylene glycol/pyridine ethylene glycol urea/glycerol dextrose levonic acid ethylene glycol/glycerol

benzene toluene toluene benzene toluene benzene ethyl benzene toluene toluene benzene/toluene toluene benzene

aromatic

hexane heptane heptane hexane hexane/cyclohexane hexane octane heptane heptane hexane heptane hexane

23 24 25 26 27 3 28 29 30 31 2 4

ethylene glycol/sulfolane glycerol/phenyl acetic acid malonic acid/urea

benzene benzene/toluene/ethyl benzene/p-xylene

cyclohexane benzene

32 33

Table 2. Chemicals Used in this Work chemical

provenance

CAS reg. no.

puritya (mass fraction)

purification method

water contentb(mass fraction purity)

choline chloride monoethylene Glycol diethylene Glycol triethylene Glycol monoethanolamine diethanolamine triethanolamine benzene thiophene cyclohexane n-hexadecane

Merck Shazand Petrochemical Co. Shazand Petrochemical Co. Shazand Petrochemical Co. Shazand Petrochemical Co. Shazand Petrochemical Co. Shazand Petrochemical Co. Merck Merck Merck Merck

67-48-1 107-21-1 111-46-6 112-27-6 141-43-5 111-42-2 102-71-6 71-43-2 110-02-1 110-82-7 544-76-3

≥99 ≥99.8 ≥99.8 >99 ≥99 ≥98.5 ≥99 ≥99.5 ≥99 ≥99 ≥99

recrystallization NA NA NA NA NA NA NA NA NA NA

≤0.5% ≤0.08% ≤0.05% ≤0.05% ≤0.2% ≤0.15% ≤0.2% NA NA ≤0.01% NA

a

As stated by the supplier bA Metrohm Karl Fischer Titrator (915 KF Ti-Touch) was used for the determination of water content.

choline chloride was used as an HBA in combination with monoethylene glycol (MEG), diethylene glycol (MEG), triethylene glycol (MEG), monoethanolamine (MEA), diethanolamine (DEA), and triethanolamine (TEA) as hydrogen bond donors for benzene or thiophene extraction from their binary mixtures with cyclohexane or hexadecane. The liquid− liquid extraction for several systems containing cyclohexane or hexadecane + benzene or thiophene + DESs was measured at T = 298.15 to 308.15 K and atmospheric pressure. The obtained LLE data were correlated by the nonrandom two-liquid (NRTL) and universal quasi-chemical (UNIQUAC) models. Evaluation of the solutes’ miscibility in the studied DESs was done by Hansen solubility parameters.

tion (LLE) in a multistage process. On the basis of this study, tetrabutylammonium bromide:sulfolane (1:7) showed the best extraction efficiency (35%) in comparison to the others. The other solvents for benzene separation from n-hexane were introduced by Rodriguez et al.3 They used tetrahexylammonium bromide (THABr) in combination with glycerol or ethylene glycol at a 1:2 mole ratio. The measured liquid−liquid equilibrium (LLE) results indicated that the studied DESs were the proper solvents for aromatics separation from naphtha. Toluene extraction from n-heptane using ethyltriphenylphosphonium (ETPPI)-based DESs24 is the other case that was studied by Kareem et al. They used a variety of DESs that were prepared by ethyl triphenylphosphonium iodide (ETPPI) in combination with sulfolane or ethylene glycol as (HBDs). They obtained LLE data that indicated that the DES (ETPPI:sulfolane (1:4)) improved separation performance. The selectivity values in the studied system were higher than those reported for sulfolane. Choline chloride is available in the industrial scale and is the cheapest HBA for use in the synthesis of DESs. Ethylene glycol indicated good results in combination as an HBD with ChCl in aromatic−aliphatic separation, which is available in the industrial scale. Meanwhile, ethanolamine series have good performance in gas sweetening, but they were not used as HBDs for aromatic−aliphatic separation. In addition, in this work,

2. EXPERIMENTAL SECTION 2.1. Materials Required. Choline chloride was our ammonium salt and hydrogen bond acceptor (HBA). Ethanol was used for the recrystallization of choline chloride. The mono-, di-, and triethylene glycol, and mono-, di-, and triethanolamine were used as HBDs. A report of the used chemicals, their specifications, sources, and purities is listed in Table 2 and Table S1. 2.2. Apparatus and Procedure. Density and speed of sound measurements were performed using a vibrating tube densimeter with an approximate frequency of 3 MHz (Anton B



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Table 3. Experimental Values of the Density (d), Speed of Sound (u), Refractive Index (nD), and Viscosity (η) of Pure DESs at T = 288.15−303.15 K and P = 0.0865 MPaa,b 10−3·d (kg·m−3)

η (mPa·s)

nD u (m·s−1)

T (K)

expt

288.15 293.15 298.15 303.15

1.115915 1.113087 1.110235 1.107339

1931.83 1920.11 1908.60 1897.08

288.15 293.15 298.15 303.15

1.113726 1.111865 1.109071 1.106165

1919.55 1907.54 1895.17 1883.53

288.15 293.15 298.15 303.15

1.117434 1.114606 1.111754 1.108858

1764.71 1752.27 1740.27 1728.43

288.15 293.15 298.15 303.15

1.115245 1.113384 1.110590 1.107684

1752.12 1740.13 1728.43 1716.35

288.15 293.15 298.15 303.15

1.120953 1.118125 1.115273 1.112377

1660.45 1648.37 1636.81 1624.86

288.15 293.15 298.15 303.15

1.118764 1.116265 1.113745 1.111203

1641.25 1629.71 1617.84 1605.83

288.15 293.15 298.15 303.15

1.091275 1.088112 1.085179 1.082217

1.05151 (1:6)52 1.076751 1.04436 (1:6)52 1.05151 (1:6)52

2006.13 1994.47 1982.01 1970.67

288.15 293.15 298.15 303.15

1.090056 1.086893 1.083961 1.080998

1.04446 (1:8)52

1989.46 1977.81 1965.34 1953.01

288.15 293.15 298.15 303.15

1.104579 1.101416 1.098483 1.095521

288.15 293.15 298.15 303.15

1.102457 1.099487 1.096433 1.092860

288.15 293.15 298.15 303.15

1.125757 1.122895 1.120116 1.117578

1734.74 1723.73 1712.20 1700.46

288.15 293.15

1.124873 1.122221

1715.54 1703.07

lit.

1.03717 (1:8)52 1.10203 (1:6)52

1.09596 (1:6)52 1.10111 (1:8)52

1.09492 (1:8)52

1839.02 1825.67 1811.70 1799.07 1826.44 1812.50 1798.84 1783.96

expt DES 1 1.4732 1.4711 1.4687 1.4668 DES 2 1.4670 1.4649 1.4628 1.4610 DES 3 1.4857 1.4836 1.4814 1.4795 DES 4 1.4797 1.4776 1.4754 1.4735 DES 5 1.4980 1.4971 1.4947 1.4928 DES 6 1.4920 1.4912 1.4887 1.4872 DES 7 1.4934 1.4913 1.4891 1.4873 DES 8 1.4905 1.4884 1.4862 1.4844 DES 9 1.4920 1.4902 1.4877 1.4861 DES 10 1.4892 1.4871 1.4850 1.4831 DES 11 1.4926 1.4905 1.4883 1.4865 DES 12 1.4900 1.4877

C

lit.

expt 43.394 35.753 28.862 22.716

lit.

2250

32.074 24.340 17.712 12.1865 125.797 118.156 111.268 105.111 110.121 102.387 95.757 90.232 160.222 152.581 145.692 139.544 144.030 136.296 129.666 124.141

1.4830

53

45.127

59.655 52.014 37.685 38.977

51.7252

50.121 42.387 35.757 30.232

48.8152

528.220 520.582 513.691 507.541

567.0052

506.302 498.568 491.940 486.414

565.3052

552.671 545.032 538.144 531.991 522.910 515.176



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Table 3. continued 10−3·d (kg·m−3) T (K) 298.15 303.15

expt 1.119729 1.116882

η (mPa·s)

nD lit.

−1

u (m·s )

expt DES 12 1.4856 1.4835

1691.25 1678.46

lit.

expt

lit.

508.547 503.024

a

Standard uncertainties (u) for pressure and temperature (temperature of density and speed of sound/temperature of refractive index and viscosity) are u(P) = 0.001 MPa and u(T) = [0.01 K for density and speed of sound/0.2 K for refractive index and viscosity], u(DES composition) = 0. 01 mole ratio, u(d) = 1.1 kg·m−3, u(u) = 1.0 m·s−1, u(nD) = 1 × 10−3, and u(η) = 0.02 mPa·s. bReference52 provides density and viscosity values for DES (ChCl:MEA) 1:6 (mole ratio), (ChCl:MEA) 1:8 (mole ratio), (ChCl:DEA) 1:6 (mole ratio), and (ChCl:MEA) 1:8 (mole ratio) only.

The experimental LLE data were determined at T = 303.15 to 308.15 K and atmospheric pressure. The equilibrium cell method was used for the determination of the LLE data. In this method, certain quantities of thiophene, benzene, cyclohexane, hexadecane, and the solvents were put into the sealed 15 mL gas chromatography (GC) vials. The stirrer was used to well mix the prepared systems at 500 rpm for 4 h. The mixed systems were left in a thermostatic bath to settle overnight. After reaching equilibrium and phase separation, the hydrocarbon and solvent phases were sampled by a needle syringe and then were analyzed using gas chromatography (GC). The experimental LLE data were determined with the GC (Varian 3800) connected to the CP-Wax 52 CB (30 m × 0.25 mm × 1.25 μm) column and FID-type detector. The analysis conditions were as follows: Start from T = 323.15 K (1 min). The temperature by a rate of 1 K/min increases to T = 343.15 K. The temperature by a rate of 20 K/min increases to T = 393.15 K, and the temperature by a rate of 40 K/min increases to T = 523.15 K at last and remains in the temperature of T = 523.15 K (for 20 min). He gas was the carrier gas, and the injector and detector temperatures were held at T = 473.15 and 523.15 K, respectively. The preferred injection split ratio was 30/70. The hydrocarbon phase samples were injected without any dilution. The studied DESs have low vapor pressure; therefore, samples of our solvent phase were injected to the GC after 10 times of dilution with ethanol. The sample injection amounts were 1 and 5 μL for the hydrocarbon phase and the diluted solvent phase, respectively. Finally, the measurements were done at least three times, and those averages were reported as our results; the relative standard deviation in this test is less than 1% (mass fraction). 2.3. Preparation of DESs. At the beginning, adequate amounts of ammonium salt (the recrystallized choline chloride) and hydrogen bond donors (HBDs) were mixed in a reaction flask (three-neck flask (250 mL)) at approximately T = 373.15 K until a transparent eutectic solvent was obtained.35 2.4. Characterization of DESs. The experimental values of density, speed of sound, refractive index, and viscosity for the studied DESs are reported in Table 3. The results show that the d, u, nD, and η values of all studied DESs are decreased with increasing of temperature or HBD mole ratio. Also, the d, u, and η values belonging to ethylene glycol- or ethanolamine-based DESs are decreased in this order: tri- > di- > mono-. Despite this behavior, nD values is increased as tri- < di- < mono-. The minimum density values belonging to DES ChCl:MEA (1:5) and DES ChCl:MEG (1:5) show the smallest viscosity. On the basis of our knowledge, there are not enough thermophysical property data for similar DESs in the literature. The comparison of thermophysical properties for the studied DESs with ones reported in the literature shows the good agreement between

Paar, DSA 5000 densimeter and speed of sound analyzer), calibrated with dried air and doubly distilled water at atmospheric pressure. Density and speed of sound are extremely sensitive to temperature, so temperature was kept constant using the Peltier device built-in densimeter with a repeatability and accuracy of ±0.001 and ± 0.01 K, respectively. The uncertainties of density and speed of sound measurements were ± 1.1 kg·m−3 and ± 1.0 m·s−1, respectively. The viscosities were measured with a glass CannonUbbelohde viscometer with a kinematic viscosity range of 1.024 × 10−6 (m2·s−1) for pure DESs and a glass CannonUbbelohde viscometer with a kinematic viscosity range of 0.0032 × 10−6 (m2·s−1) for the dilute region, respectively. These viscometers were calibrated with doubly distilled water. Viscosity of the samples (η) was obtained by the following equation η K = Lt − d t

(1)

where d is the density, t is the flow time of the mixture, and L and K are the viscometer constants. A digital stopwatch with a remixture of 0.01 s was used to measure the flow time. The estimated uncertainty of the experimental viscosity was ±0.02 mPa·s. The refractive index was measured with a digital refractometer (ATAGO DRA1, Japan) and an uncertainty of ±0.001. The refractometer temperature controller was a water bath with an uncertainty of ±0.01 K using a Hetotherm PF (Heto Lab Equipment, Denmark) thermostat. The analytical balance (AND, GR202, Japan) with the precision of ±10−8 kg was used for the preparation of mixtures in molal bases. The studied mixtures were prepared in well-sealed glass vials to avoid contamination or mixture evaporation. Measurements were done continually after the mixtures’ preparation. The solubility of solutes including hexadecane, cyclohexane, benzene, and thiophene in our studied solvents was measured by a turbidity test method at T = 298.15 K and atmospheric pressure.34 In this method, approximately 4 g of solvents was placed into the 15 mL glass vials, and a quantitative amount of the solute (hexadecane, cyclohexane, benzene, and thiophene) was added gradually under a uniform mixing rate till slight turbidity was obtained in the solution. Table 3 shows the results of the turbidity test for benzene, thiophene, hexadecane, and cyclohexane in the studied systems in mole fraction. The tests were done at least three times, and those averages were reported as our results; the relative standard deviation in this test is less than 1% (mass fraction). D



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Table 4. Solubility of Cyclohexane, Hexadecane, Benzene, and Thiophene in the DESsa,b DES (mole ratio)

abbreviation

molar mass

water content(mass fraction purity)

xcyclohexane

xhexadecane

xbenzene

xthiophene

choline chloride:monoethylene glycol (1:5) choline chloride:monoethylene glycol (1:7) choline chloride:diethylene glycol (1:5) choline chloride:diethylene glycol (1:7) choline chloride:triethylene glycol (1:5) choline chloride:triethylene glycol (1:7) choline chloride:monoethanolamine (1:5) choline chloride:monoethanolamine (1:7) choline chloride:diethanolamine (1:5) choline chloride:diethanolamine (1:7) choline chloride:triethanolamine (1:5) choline chloride:triethanolamine (1:7)

DES 1 DES 2 DES 3 DES 4 DES 5 DES 6 DES 7 DES 8 DES 9 DES 10 DES 11 DES 12

75.00 71.76 111.70 110.31 148.41 148.85 74.17 70.90 110.89 109.45 147.59 147.99

0.47 0.54 0.45 0.48 0.52 0.55 0.43 0.45 0.46 0.50 0.48 0.51

0.019 0.020 0.020 0.021 0.017 0.029 0.026 0.027 0.025 0.021 0.028 0.025

0.007 0.008 0.008 0.009 0.010 0.011 0.011 0.012 0.013 0.014 0.013 0.015

0.04235 0.03335 0.03535 0.03135 0.02735 0.02335 0.11435 0.09235 0.10935 0.08935 0.09535 0.07835

0.07135 0.06235 0.06735 0.06235 0.06235 0.05835 0.14535 0.11235 0.11135 0.09835 0.10635 0.09635

a

The solubility tests were measured at T = 298.15 K and P = 0.0865 MPa. bStandard uncertainties u are u(DES composition) = 0.01 mole ratio, u(T) = 0.1 K, u(x) = 0.0015, and u(P) = 0.001 MPa.

correct if the ratio between the constituents does not change, which means that DESs stay intact in one phase only (no losses to the raffinate phase). On the basis of gas chromatography results, there are not any other components in the aliphatic phase than hexadecane, cyclohexane, benzene, or thiophene (Tables S2 and S3). However, the validation of GC results was done by a 1H NMR spectrometer (Brucker Av-300) for {hexadecane + benzene or thiophene + DES 7} systems, proving the nonappearance of any individual compounds of DES 7 in the raffinate phase (Figure S1). This means that the proportion of the two components of DES will remain unchanged in the DES phase after LLE. Thus, GC results are confirmed by the 1H NMR spectrometer, and the assumption of considering DESs as a pseudo-pure species is justified. To evaluate the performance of the studied DESs, the compositions of equilibrium liquid phases for our best resultant DESs in the two introduced series including hexadecane or cyclohexane/benzene or thiophene/DESs are shown in Tables S2 and S3. The three-dimensional curves of the studied systems including DES 7 are plotted in Figures 1 and 2. The extraction efficiency can be determined by two factors: the distribution coefficient (β) and the selectivity (S). The distribution coefficient (β) depends on the tie-line slope in which, by increasing the distribution coefficient, the number of extraction stages decreases. The selectivity (S) indicates the ability of a solvent in the solvation of a target solute without solving other contaminations from the initial mixture. These values were calculated via the following equations

experimental and literature data in density values as shown in Table 3. Also, the observed small differences between our viscosity values and those reported in the literature may be related to the HBD:HBA mole ratio differences and the DESs water content.

3. RESULTS AND DISCUSSION 3.1. Solubility Results. DESs indicate the upper solubility for aromatic compounds and lower solubility for aliphatic compounds, which prove the applicability of these neoteric extraction agents for liquid−liquid extraction. The process temperature and the viscosity are two key factors for the results of solubility tests. As it can be seen in Table 4, all of our prepared DESs show higher solubility for benzene and thiophene in comparison to hexadecane and cyclohexane. It can be related to the π electrons in aromatic molecules (benzene and thiophene), which cause effective interaction among solutes (thiophene and benzene) and solvents. The solubility increases with stronger interactions. In nonaromatic compounds (hexadecane and cyclohexane), there are not any π electrons; therefore, its lower solubility is a result of weaker interactions. The hexadecane molecules have the weakest interactions and lower solubility in the DESs (solvent). Cyclohexane shows better solubility than that of hexadecane in the studied DESs, which may show the influence of hexadecane’s larger molecular chain in its lower solubility than that of cyclohexane. Also, thiophene solubility in the studied solvents is higher than that of benzene in which DES 7 (choline chloride:MEA) with a 1:5 mole ratio indicates higher solubility for aromatics (benzene and thiophene) than that of other studied solvents. The solubility reduction trend for aromatics (thiophene and benzene) was DES 7 > DES 9 > DES 11 for the ethanolamine series and DES 1 > DES 3 > DES 5 for the ethylene glycol series, which means that ethanolamine-based DESs have better solubility for benzene or thiophene than that of ethylene glycol-based DESs, and in the studied DESs, the 1:5 mole ratio shows better performance than that of 1:7 for aromatic solubility. As it can be seen in Table 4, an increase in the HBD mole ratio (in the DES composition) causes an increase of nonaromatics’ solubility and decreases the studied aromatics’ (benzene and thiophene) solubility. 3.2. Liquid−Liquid Equilibria. In this section, we measured pseudo-ternary liquid−liquid equilibrium (LLE) data. The assumption to treat DESs as a single species is only

β=

x 2II x 2I

(2)

where xI2 and xII2 are benzene and thiophene mole fractions in the aliphatic and DES phases, respectively. S=

x 2IIx1I x 2Ix1II

(3)

Figures 1 and 2 indicate the triangular phase diagrams of the best resultant ternary mixtures including cyclohexane or hexadecane + benzene + DES 7 and cyclohexane or hexadecane + thiophene + DES 7. The studied aromatics (benzene and thiophene) are completely miscible in cyclohexane and hexadecane and partially immiscible with the DESs. With regard to a classification by Sorensen et al., the obtained ternary phase diagrams are type II, which show wide immiscibility areas E



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Figure 1. Solid circles, squares, and triangles are related to the experimental and calculated (NRTL and UNIQUAC) LLE data. Solid lines, dashed lines, and dotted lines are related to the experimental and calculated (NRTL and UNIQUAC) tie lines for the ternary mixture of (a) {hexadecane + benzene + DES 7} and (b) {hexadecane + thiophene + DES 7} at a temperature of 298.15 K and atmospheric pressure.

Figure 2. Solid circles, squares, and triangles are related to the experimental and calculated (NRTL and UNIQUAC) LLE data. Solid lines, dashed lines, and dotted lines are related to the experimental and calculated (NRTL and UNIQUAC) tie lines for the ternary mixture of (a) {cyclohexane + benzene + DES 7} and (b) {cyclohexane + thiophene + DES 7} at a temperature of 298.15 K and atmospheric pressure.

between cyclohexane or hexadecane (nonaromatics) and DESs.36 Also, it can be understood from the positive slopes of the tie lines that the solubility of aromatics (thiophene and benzene) are higher than cyclohexane’s or hexadecane’s solubility. In the case of DES 7-including systems, almost the whole triangular diagram area was covered with the tie lines, which shows the high ability of DES 7 for aromatics (thiophene and benzene) extraction from nonaromatic media in comparison with conventionally used solvents (NFM and SULF). The parameters (S and β) are two key factors to evaluate the performance of the studied DESs as solvents in the aromatics/ nonaromatics separation. The S and β values are reported in Tables S2 and S3 and then plotted in Figures 3 and 4. The obtained S values for the studied systems are higher than unity showing that these DESs can be used as solvents for aromatic− nonaromatic separation. Also, it can be seen that the solute distribution ratios (β) are lower than 1, which shows that a large amount of solvent will be required for this separation, but it

would be compensated by the absence of DESs in the aliphatic (nonaromatic) phase and low vapor pressures of the DESs, which paves the way for recovery of the solvent after extraction.4 As it can be seen in Figures 3 and 4, the S and β values decrease with the increase of the aromatics’ (benzene and thiophene) concentration in the nonaromatic (cyclohexane or hexadecane) phase. The aromatic compounds’ structures have influence on the S and β values. Thiophene shows higher S and β values in comparison to benzene. This result might be addressed as due to thiophene or benzene’s polarity. The presence of sulfur atoms in the aromatic ring enhance their interaction with our studied DESs and lead to the higher S and β values. Benzene has a lower polarity in comparison to thiophene, and lower S and β values were expected in benzene-containing ternary mixtures.37 A higher selectivity means a higher aptitude for the solvent to F



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Figure 3. Experimental solute distribution coefficients (β) as functions of the benzene and thiophene mole fraction in the aliphatic-rich phase for the ternary mixtures of {hexadecane + thiophene + DES 7} (open square), {hexadecane + thiophene + DES 1} (open triangle), {cyclohexane + benzene + DES 7} (open circle), and {cyclohexane + benzene + DES 1} (open diamond) at 298.15 K and atmospheric pressure.

Figure 5. (a) Solute distribution coefficients and (b) the selectivity values as functions of the aromatic content in the aliphatic-rich phase for the system {cyclohexane + benzene + DESs} at T = 298.15 K and atmospheric pressure. The studied DESs were tetrabutylammonium bromide:sulfolane with a 1:7 mole ratio by Salleh32 and DES 7 (choline chloride:monoethanolamine) with a 1:5 molar ratio, which were compared with the recently studied ionic liquid (1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide) by Hadj-Kali et al.53 Figure 4. Experimental selectivity values (S) as functions of the benzene and thiophene mole fraction in the aliphatic-rich phase for the ternary mixtures of {hexadecane + thiophene + DES 7} (open square), {hexadecane + thiophene + DES 1} (open triangle), {cyclohexane + benzene + DES 7} (open circle), and {cyclohexane + benzene + DES 1} (open diamond) at 298.15 K and atmospheric pressure.

to the industrial aspect of our work, which is related to the use of an industrially available ammonium salt (choline chloride), it can be understood that this research suggested DESs can be prepared with cheaper costs, which paves the way to use them in the industrial application. The recyclability of the best resultant DES (DES 7) was investigated at a temperature of 373.15 K for 5 cycles. The LLE experimental data (Table S4) indicate that the distribution ratio and selectivity remained constant after 5 regeneration cycles, which shows the reusability of this DES after these regeneration cycles. 3.3. Consistency of Tie-Line Data. The Othmer−Tobias equation38 was used to ensure the consistency of measured LLE data.

extract benzene or thiophene (aromatics) from cyclohexane or hexadecane (nonaromatics) and result in a lower contamination of nonaromatic phases with aromatic compounds. As it can be seen in Figure 5, our studied DES 7 shows better selectivity than that of a recently studied DES (tetrabutylammonium bromide:sulfolane) with a 1:7 mole ratio by Salleh et al.32 and ionic liquid (1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl) imide) studied recently by Hadj-Kali et al..53 It is noticeable that this difference between DES 7 (S = 28.53) and tetrabutylammonium bromide:sulfolane (1:7) (S = 13.69) including systems at xbenzene ≈ 0.1 is approximately 2-fold. A higher selectivity means a higher aptitude for the solvent to extract benzene (aromatics) over cyclohexane (non-aromatic) and result in a lower contamination of nonaromatic phases with aromatic compounds. However, both of the studied DESs have lower β values than those of the studied ionic liquid. With regard

HC y DES y ij 1 − wHC ij 1 − wDES zz zz jj z zz lnjjjj ln = + A B z j HC DES z j z (4) k wHC { k wDES { where w relates to the mass fraction of the hydrocarbon (HC) including hexadecane or cyclohexane in the HC-rich phase and deep eutectic solvents (DESs) in the DES phase, and A and B are parameters of the Othmer−Tobias equation. The parameters

G



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and correlation factors (R2) were determined using a partial least

are shown in Figure 6. As seen in Table 5 and Figure 6, the closeness of R2 to unity and the linearity of the plot mention the good degree of consistency of measured LLE data for the studied systems.

square regression. The obtained results from the correlation for the studied systems are reported in Table 5, and its related plots Table 5. A and B Constants of the Othmer−Tobias Equation for the Studied Systems at T = 298.15 K and Atmospheric Pressure Othmer−Tobias correlation systems

A

hexadecane/benzene/DES DES 1 −0.048 DES 2 −0.052 DES 3 −0.054 DES 4 −0.051 DES 5 −0.070 DES 6 −0.117 DES 7 −0.049 DES 8 −0.050 DES 9 −0.064 DES 10 −0.075 DES 11 −0.076 DES 12 −0.094 hexadecane/thiophene/DES DES 1 −0.035 DES 2 −0.058 DES 3 −0.048 DES 4 −0.051 DES 5 −0.059 DES 6 −0.069 DES 7 −0.026 DES 8 −0.034 DES 9 −0.044 DES 10 −0.043 DES 11 −0.058 DES 12 −0.070 cyclohexane/benzene/DES DES 1 −0.041 DES 2 −0.136 DES 3 −0.100 DES 4 −0.163 DES 5 −0.100 DES 6 −0.160 DES 7 −0.026 DES 8 −0.056 DES 9 −0.042 DES 10 −0.070 DES 11 −0.087 DES 12 −0.163 cyclohexane/thiophene/DES DES 1 −0.037 DES 2 −0.057 DES 3 −0.044 DES 4 −0.116 DES 5 −0.077 DES 6 −0.129 DES 7 −0.037 DES 8 −0.067 DES 9 −0.036 DES 10 −0.113 DES 11 −0.047 DES 12 −0.082

B

R2

−2.848 −2.845 −2.842 −2.846 −3.063 −3.676 −2.669 −2.668 −2.975 −3.212 −3.112 −3.342

0.998 0.995 0.998 0.999 0.999 0.997 0.998 0.999 0.997 0.997 0.998 0.999

−2.687 −3.260 −3.181 −3.254 −3.314 −3.477 −2.599 −2.756 −3.047 −3.044 −3.250 −3.463

0.997 0.997 0.996 0.998 0.997 0.995 0.999 0.998 0.999 0.997 0.997 0.997

−5.060 −5.419 −5.519 −5.723 −5.631 −5.688 −4.552 −4.822 −4.772 −5.109 −5.241 −5.649

0.996 0.995 0.995 0.996 0.992 0.997 0.996 0.997 0.995 0.997 0.997 0.996

−4.784 −4.875 −5.118 −5.290 −5.308 −5.570 −4.514 −4.976 −4.668 −5.512 −5.154 −5.375

0.997 0.997 0.993 0.998 0.998 0.998 0.993 0.996 0.995 0.999 0.993 0.995

Figure 6. Othmer−Tobias plots for the {n-hexadecane or cyclohexane + thiophene or benzene + DES 7 (choline chloride: monoethanolamine (1:5))} systems at 298.15 K and atmospheric pressure: {hexadecane + thiophene + DES 7} (open square), {hexadecane + benzene + DES 7} (open diamond), {cyclohexane + thiophene + DES 7} (cross), and {cyclohexane + benzene + DES 7} (open triangle).

3.4. LLE Data Correlation. The experimental ternary LLE data measured in this study were correlated using the nonrandom liquid equation (NRTL) proposed by Renon and Prausnitz39 and the universal quasi-chemical (UNIQUAC) theory developed by Abrams and Prausnitz.40 The obtained results are reported in Tables 6 and 7 for NRTL and Tables 9 and 10 for UNIQUAC parameters. 3.5. NRTL Model. The NRTL equation can be used for highly nonideal systems as well as for partially miscible systems.40 The activity coefficients (γi) in the NRTL model for each component (i) of studied ternary mixtures are calculated by the following equation for multicomponent systems m

ln γi =

∑ j = 1 τjiGjixj m

∑l = 1 Glixl

m

+

∑ j=1

m ij y jjτ − ∑r = 1 τrjGrjxr zzz jj ij z m m ∑l = 1 Gljxl zz ∑l = 1 Gljxl j k {

Gijxj

(5)

Gji = exp( −αjiτji) and α = αji = αji

τji =

gji − gji RT

=

Δgji RT (6)

where g is an energy parameter representing the interaction of the species, x is the mole fraction of components, and R is the universal gas constant. Although the parameter of α can be used as an adjustable parameter, in our study, the parameter α was set equal to 0.3.41 3.6. UNIQUAC Model. The activity coefficients (γi) for the UNIQUAC model for each component (i) of the studied ternary mixtures are given by H



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Table 6. NRTL Binary Parameters Obtained for the Ternary Systems {Cyclohexane (1) + Benzene or Thiophene (2) + DES (3)} at α = 0.3 and T = 298.15 K Δgij (kJ·mol−1)

ij

DES type in the system Benzene DES 1

12 13 23 12 13 23 12 13 23 12 13 23 12 13 23 12 13 23 12 13 23 12 13 23 12 13 23 12 13 23 12 13 23 12 13 23

DES 2

DES 3

DES 4

DES 5

DES 6

DES 7

DES 8

DES 9

DES 10

DES 11

DES 12

Δgji (kJ·mol−1)

4.952 −15.991 22.644 5.111 −15.751 25.123 5.457 −15.618 23.152 5.999 −16.367 23.728 6.122 −16.672 24.058 6.364 −17.602 25.398 5.457 −15.618 23.152 5.999 −16.367 23.728 6.028 −15.274 24.068 6.352 −15.924 25.036 7.142 −16.398 26.394 7.632 −17.612 26.931

31.515 26.975 11.140 36.308 26.566 11.981 38.427 36.223 10.838 43.511 26.779 10.932 41.026 25.362 9.288 45.024 24.361 9.038 23.427 36.223 10.838 28.511 26.779 10.932 30.285 35.237 10.051 31.252 36.211 10.632 31.965 37.126 11.036 32.064 38.205 11.342

DES type in the system

rmsd 0.0216

Thiophene DES 1

0.0648

DES 2

0.0320

DES 3

0.0407

DES 4

0.0286

DES 5

0.0462

DES 6

0.0279

DES 7

0.0290

DES 8

0.0339

DES 9

0.0387

DES 10

0.0522

DES 11

0.0377

DES 12

m

ln γi = ln

Φi Φ θ z + qi ln i + li − i ∑ xjl j − qi ln(θτ j ji) Φi xi 2 xi j = 1 m

+ qi − qi∑ j=1

Φi =

rx i i m ∑ j = 1 rjxj

, θi =

qi =

k

m

qx

i i , lj m ∑ j = 1 qjxj

(7)

=

ij −Δuij yz zz − (rj − 1), and τji = expjjj j RT zz k {

z (rj − qj) 2

Rk = (8)

Qk =

where the coordination number (z) was set as z = 10. The parameters qi and ri are the molecular surfaces and molecular van der Waals volumes for the pure component i, respectively. These parameters were calculated by the sum of the group volume (Rk) and group area (Qk) parameters with the following equations: ri =

∑ νkiR k k

Δgij (kJ·mol−1)

Δgji (kJ·mol−1)

rmsd

12 13 23 12 13 23 12 13 23 12 13 23 12 13 23 12 13 23 12 13 23 12 13 23 12 13 23 12 13 23 12 13 23 12 13 23

7.856 −15.302 23.216 6.834 −15.892 22.515 6.125 −16.245 24.311 6.892 −16.328 25.013 7.266 −16.307 25.311 8.092 −15.721 26.345 5.720 −16.384 22.200 5.921 −16.207 21.648 6.302 −15.987 22.771 7.014 −16.726 20.674 7.216 −15.059 24.032 7.618 −16.027 25.096

24.342 35.463 12.716 26.285 25.232 11.724 25.142 34.628 11.025 26.354 26.037 10.277 26.289 24.268 10.692 25.311 24.708 9.087 26.368 24.929 10.416 23.456 24.862 10.626 22.169 23.065 9.048 21.678 24.062 10.933 24.035 22.084 10.267 25.037 22.091 10.923

0.0450

0.0401

0.0467

0.0452

0.0402

0.0366

0.0330

0.0183

0.0271

0.0289

0.0375

0.0358

(10)

Here, νik is the number of k-type groups in the i molecule. The parameters of Qk and Rk were determined by van der Waals group volumes (ri) and surface areas (qi), which are listed in Table 8. Also, parameters of Vk and Ak were estimated from the UNIFAC group contributions proposed by Prausnitz.40,42

θτ j ji ∑k = 1 θkτkj

∑ νkiQ k

ij

Vk 15.17

(11)

Ak 2.5 × 109

(12)

The constant values of 15.17 and 2.5 × 109 are related to the standard segment volume and the standard segment area for the methylene group, respectively.43 Δgji and Δuji are two adjustable parameters, which have to be fitted for both thermodynamic models. For our studied systems (cyclohexane or hexadecane + benzene or thiophene + DES),

(9) I



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Table 7. NRTL Binary Parameters Obtained for the Ternary Systems {Hexadecane (1) + Benzene or Thiophene (2) + DES (3)} at α = 0.3 and T = 298.15 K DES type in the system Benzene DES 1

DES 2

DES 3

DES 4

DES 5

DES 6

DES 7

DES 8

DES 9

DES 10

DES 11

DES 12

ij 12 13 23 12 13 23 12 13 23 12 13 23 12 13 23 12 13 23 12 13 23 12 13 23 12 13 23 12 13 23 12 13 23 12 13 23

Δgij(kJ·mol−1)

Δgji(kJ·mol−1)

6.274 −14.312 25.530 6.724 −13.421 26.939 5.552 −14.364 22.098 6.241 −15.342 22.365 7.231 −16.327 25.871 7.216 −14.742 24.234 6.248 −14.648 25.001 6.428 −14.585 26.535 6.324 −14.274 25.241 7.541 −14.221 24.655 8.142 −15.241 22.234 6.125 −16.421 21.404

18.256 23.822 9.003 16.236 25.437 10.794 16.429 24.152 9.245 23.421 24.245 9.287 24.210 23.102 10.156 25.321 22.124 10.241 21.745 17.853 9.407 11.580 18.587 10.151 22.124 19.214 09.034 12.245 16.214 9.254 11.242 17.235 12.521 12.711 18.420 13.244

DES type in the system

rmsd 0.0342

Thiophene DES 1

0.631

DES 2

0.267

DES 3

0.421

DES 4

0.365

DES 5

0.0397

DES 6

0.0341

DES 7

0.0302

DES 8

0.0429

DES 9

0.0288

DES 10

0.0489

DES 11

0.0271

DES 12

component

van der Waals group volumes (r)

surface area (q)

3.795 3.795 3.187 2.856 23.461 30.912 31.006 41.474 38.550 52.037 19.521 25.395 33.464 44.916 44.473 60.328

4.285 4.954 2.400 2.140 21.614 28.017 29.895 39.611 38.176 51.204 20.299 26.176 28.303 34.713 40.819 54.904

Δgij(kJ·mol−1)

Δgji(kJ·mol−1)

rmsd

12 13 23 12 13 23 12 13 23 12 13 23 12 13 23 12 13 23 12 13 23 12 13 23 12 13 23 12 13 23 12 13 23 12 13 23

4.952 −15.991 22.644 5.111 −15.751 25.123 4.241 −14.234 25.452 5.442 −14.124 24.452 6.144 −15.241 25.441 7.448 −15.454 26.745 5.457 −15.618 23.152 5.999 −16.367 23.728 7.552 −15.987 24.144 6.742 −15.554 22.625 6.632 −14.442 25.557 6.324 −14.663 22.811

31.515 26.975 11.14 36.308 29.566 11.981 30.145 28.642 10.854 37.241 27.245 11.214 36.214 25.746 10.141 34.785 24.773 10.880 23.427 36.223 10.838 28.511 26.779 10.932 20.554 27.414 11.165 24.446 25.141 9.037 25.245 24.842 11.654 22.674 25.011 9.162

0.0362

0.0452

0.0469

0.0243

0.0367

0.0315

0.0299

0.0316

0.0236

0.0317

0.0418

0.0469

interaction parameters were not reported previously in the literature. For NRTL and UNIQUAC models, binary interaction parameters were calculated with minimizing the differences among the experimental and the computational mole fractions (OF).

Table 8. UNIQUAC r and q Parameters for the Used Components cyclohexane hexadecane benzene thiophene DES 1 DES 2 DES 3 DES 4 DES 5 DES 6 DES 7 DES 8 DES 9 DES 10 DES 11 DES 12

ij

m

OF =

n

∑ ∑ [(xijI,exp − xijI,cal)2 + (xijII,exp − xijII,cal)2 ] i=1 j=1

(13)

Here, m is the number of the tie lines, and n is the number of components. The root mean square deviation (rmsd) of the mixtures (σx) was obtained by ij m − 1 n − 1 (x I,exp − x I,cal)2 + (x II,exp − x II,cal) yz ij ij ij ij j zz zz σx = 100 jjj ∑ ∑ jj zz 2 mn i = 1 j = 1 k {

(14)

This is a way for comparison of the experimental and the calculated mole fractions of the components for each tie-line. J



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Table 9. UNIQUAC Binary Parameters Obtained for the Ternary Systems {Hexadecane (1) + DES (2) + Benzene (3)} at T = 298.15 and 308.15 K T (K) DES 1 298.15 308.15 DES 2 298.15 308.15 DES 3 298.15 308.15 DES 4 298.15 308.15 DES 5 298.15 308.15 DES 6 298.15 308.15 DES 7 298.15 308.15 DES 8 298.15 308.15 DES 9 298.15 308.15 DES 10 298.15 308.15 DES 11 298.15 308.15 DES 12 298.15 308.15

Δu12 (kJ·mol−1)

Δu13 (kJ·mol−1)

Δu21 (kJ·mol−1)

Δu23 (kJ·mol−1)

−6.44 −7.98

−3.39 −3.81

14.10 14.06

−7.50 −7.53

−7.16 −7.52

−4.98 −3.24

−11.95 −10.97

−7.36 −7.91

−3.42 −3.12

−8.68 −8.89

Δu32 (kJ·mol−1)

rmsd

2.70 2.60

2.89 2.19

0.0248 0.0324

−6.83 −6.84

1.76 1.95

2.42 2.46

0.0287 0.0201

−10.55 −10.75

−6.24 −6.26

1.75 1.75

2.57 2.62

0.0248 0.0259

−3.87 −3.30

−12.47 −12.45

−11.10 −11.07

−1.94 −1.9

2.63 2.62

0.0128 0.0211

−7.45 −7.52

−3.75 −3.74

−9.27 −9.77

−10.34 −11.22

−1.01 −1.12

2.45 2.21

0.0275 0.0253

−7.42 −7.36

−3.42 −3.27

−7.42 −7.24

−12.47 −12.35

−2.56 −2.42

2.25 2.45

0.0314 0.0391

−8.98 −8.37

−3.85 −3.02

−0.18 −0.18

−6.14 −6.15

1.81 1.81

2.87 2.90

0.0275 0.0412

−11.68 −11.89

−3.87 −3.30

−2.47 −2.45

−11.10 −11.07

−1.94 −1.9

2.63 2.62

0.0215 0.0309

−9.54 −9.35

−3.45 −3.74

−8.42 −8.34

−11.12 −11.42

−5.21 −5.74

2.74 2.65

0.0182 0.0264

−9.65 −9.41

−3.12 −3.17

−6.74 −6.22

−12.41 −12.32

−5.54 −5.22

2.65 2.42

0.0361 0.0185

−10.99 −10.57

−3.41 −3.67

−5.21 −6.02

−12.65 −12.07

−6.38 −6.91

2.74 2.85

0.0239 0.0218

−10.44 −10.05

−3.73 −3.35

−7.47 −7.45

−12.10 −12.07

−7.94 −7.95

2.63 2.62

0.0312 0.0407

of the studied systems’ components by using Hoftyzer and Krevelen’s group contribution method47

The binary parameters and the root mean square deviation of the mixtures (σx) were calculated by the abovementioned method at T = 298.15 and 308.15 K (Tables 6, 7, 9, and 10 and Tables S5 and S6). The results obtained from the experimental and computational data indicate that NRTL and UNIQUAC models are applicable to correlate experimental values obtained from liquid−liquid equilibria. 3.7. Hansen Solubility Parameters. To obtain reliable predictive methods for a variety of important properties, it is necessary to use quantitative relationships of structure and property (QSPR).43−45 The solubility parameter method is the earliest but widely used QSPR technique.44−46 In this method, three molecular descriptors (Hansen solubility parameters or HSP) are used. This three-dimensional solubility parameter system, which was proposed by Hansen,46 is the most widely accepted one. HSP is also defined as the following δt 2 = δd 2 + δp2 + δ h 2

Δu31 (kJ·mol−1)

δd =

δp =

δh =

∑i Fdi (16)

V

∑i Fp2i V

(17)

∑i E hi V

(18)

where Fdi and Fpi are the group contributions to the dispersion and polar components per structural group to the molar attraction constant, F, proposed by Small,48 Ehi is the hydrogen bonding energy per structural group, and V is the molar volume of the molecule. The numerical values of Fdi, Fpi, and Ehi of common structural groups are listed in Table 11. The extent to which compound i likes or dislikes compound j is estimated through the radius of solubility, Rij, defined as49

(15)

where δd is the dispersion contribution, δp is the polar contribution, and δh is the hydrogen bonding contribution to HSP. Hansen’s solubility parameters were determined for each K



Article

Table 10. UNIQUAC Binary Parameters Obtained for the Ternary Systems {Cyclohexane (1) + DES (2) + Benzene (3)} at T = 298.15 and 308.15 K T (K) DES 1 298.15 308.15 DES 2 298.15 308.15 DES 3 298.15 308.15 DES 4 298.15 308.15 DES 5 298.15 308.15 DES 6 298.15 308.15 DES 7 298.15 308.15 DES 8 298.15 308.15 DES 9 298.15 308.15 DES 10 298.15 308.15 DES 11 298.15 308.15 DES 12 298.15 308.15

Δu12 (kJ·mol−1)

Δu13 (kJ·mol−1)

Δu21 (kJ·mol−1)

Δu23 (kJ·mol−1)

Δu31 (kJ·mol−1)

Δu32 (kJ·mol−1)

rmsd

−8.24 −7.52

−4.23 −4.65

12.35 12.54

−6.14 −6.65

4.24 4.52

3.26 2.47

0.0354 0.0285

−6.44 −7.98

−3.39 −3.81

14.10 14.06

−7.50 −7.53

4.70 4.60

2.89 3.19

0.0401 0.0274

−6.62 −7.58

−3.52 −3.42

14.42 14.35

−7.52 −6.41

4.54 4.32

3.44 3.64

0.0324 0.0329

−8.45 −7.41

−4.23 −4.71

13.35 14.54

−8.14 −6.65

4.24 4.52

3.26 2.47

0.0218 0.0344

−8.24 −8.52

−4.23 −4.65

12.35 13.54

−7.14 −6.65

4.24 4.52

3.26 2.47

0.0328 0.0245

−7.24 −7.52

−5.23 −4.65

12.35 14.54

−8.14 −7.65

4.24 4.52

3.26 3.47

0.0301 0.0299

−7.24 −7.52

−4.23 −5.65

12.35 14.54

−7.14 −7.65

4.24 4.52

3.26 2.47

0.0322 0.0274

−8.24 −9.52

−5.23 −4.65

14.52 13.14

−7.85 −8.45

4.67 3.75

3.74 3.44

0.0165 0.0294

−8.65 −8.44

−5.63 −4.65

14.85 14.54

−8.65 −7.56

3.74 4.58

3.88 3.64

0.0254 0.0543

−8.15 −7.68

−4.75 −5.58

12.05 13.52

−7.42 −6.58

3.63 4.05

3.85 2.36

0.0126 0.0168

−8.25 −9.85

−4.84 −5.64

12.46 13.54

−6.21 −7.65

4.78 3.82

3.18 3.05

0.0259 0.0327

−8.57 −9.05

−5.65 −4.45

12.47 12.84

−8.86 −6.59

4.06 4.59

3.67 2.43

0.02465 0.0361

tions (δd) are our dominant parameter in this order: thiophene > benzene > cyclohexane > hexadecane. This order shows the solubility of these solutes in the studied solvents. Also, the solubility radius for each series increases with this order: mono< di- < tri-, which is in agreement with our solubility test results. Then, it can be concluded that the solubility of thiophene is higher than that of benzene in our studied DESs. The highest solubility results were observed for DES 7.

Table 11. The Numerical Values of Solubility Parameter Component Group Contributions Used in Hoftyzer and Van Krevelen’s Method49 structural group

Fdi ((MJ·m−3)0.5·mol−1)

Fpi ((MJ·m−3)0.5·mol−1)

EHi (J·mol−1)

−CH3 CH2− >CH− >C< −OH O− −NH2 −NH2− >N− ring

420 270 80 −70 210 100 280 160 20 190

0 0 0 0 500 400 0 210 800 0

0 0 0 0 20000 3000 8400 3100 5000 0

4. CONCLUSIONS In this work, the performance of some novel DESs based on choline chloride and (mono-, di-, and tri-) ethylene glycols or ethanolamines in the aromatic extraction (benzene or thiophene) from nonaromatic phases (cyclohexane or hexadecane) was studied. For the initial estimation of the selected DESs’ performance in this extraction, the solubility tests were done. The obtained results show the higher solubility of the studied aromatics in the studied DESs in comparison to nonaromatics. Liquid−liquid equilibrium of the studied systems (cyclohexane/hexadecane (1) + benzene/thiophene (2) + DES (3)) were determined at T = 298.15 to 308.15 K and atmospheric pressure.

ÅÄÅ ÑÉÑ 1 1 R ij 2 = 4ÅÅÅÅ(δdi − δdj)2 + (δpi − δpj)2 + (δ hi − δ hj)2 ÑÑÑÑ ÅÅÇ ÑÑÖ 4 4

(19)

A smaller radius is equal to a higher miscibility of compound i by compound j. Table 12 indicates that the dispersion contribuL



Article

Table 12. The Solubility Parameter and the Radius of Solubility for Benzene and Thiophene in the Studied DESs solvent

solute

δh ((MPa)0.5)

δP ((MPa)0.5)

δd ((MPa)0.5)

δt ((MPa)0.5)

Rij

DES 1

benzene thiophene benzene thiophene benzene thiophene benzene thiophene benzene thiophene benzene thiophene benzene thiophene benzene thiophene benzene thiophene benzene thiophene benzene thiophene benzene thiophene

58.14

1.23

96.17

112.39

60.82

1.41

101.89

118.67

59.32

0.92

101.69

117.73

62.96

1.08

106.36

123.60

64.52

0.78

102.84

121.41

71.78

0.91

116.88

137.16

47.4

0.90

94.93

106.11

58.44

1.05

98.02

114.12

48.86

0.85

100.56

111.80

57.27

0.99

100.05

115.29

51.6

0.86

101.8

114.13

60.32

1

105.85

121.83

170.66 166.44 182.35 178.12 181.49 177.25 191.51 187.26 185.37 181.15 214.27 210.03 165.05 160.75 174.26 170.02 176.29 171.97 177.74 173.48 179.42 175.11 189.71 185.45

DES 2 DES 3 DES 4 DES 5 DES 6 DES 7 DES 8 DES 9 DES 10 DES 11 DES 12

Notes

The temperature effect on the separation process was studied. It is noticeable that the lower temperatures mean better separation in our studied systems. Regarding the distribution coefficient and selectivity, DES 7 would be the preferred DES compared to the other studied DESs in this work. The Othmer− Tobias correlation showed the high consistency of the measured LLE data. Finally, the NRTL and UNIQUAC models were successfully used to correlate the LLE data by treating the DESs as a pseudo-pure component. The Hansen solubility parameters calculations indicate that the dispersion contributions (δd) are the dominant parameter in our studied systems in which the solubility for each series of DESs is increased in this order: mono- < di- < tri-. This order is in agreement with the solubility test results. Therefore, preliminary results show that the ethanolaminebased DESs are more proper than ethylene glycol-based DESs for the extraction of aromatics from the nonaromatic (cyclohexane or hexadecane) media.

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The authors declare no competing financial interest.

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ACKNOWLEDGMENTS The authors would like to express their gratitude to the University of Tabriz Research Council for the financial support of this research.

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ASSOCIATED CONTENT

S Supporting Information *

The Supporting Information is available free of charge on the ACS Publications website at DOI: 10.1021/acs.jced.9b00313.

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REFERENCES

Chemicals used in this work, experimental LLE data, and UNIQUAC binary parameters (PDF)

AUTHOR INFORMATION

Corresponding Author

*E-mail: [email protected]. Phone: +98 4133393094. Fax: 98 4133340191. ORCID

Hemayat Shekaari: 0000-0002-5134-6330 Mohammed Taghi Zafarani-Moattar: 0000-0002-2174-1639 M



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O


Thiophene + Cyclohexane

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