Enhanced Vitamin E Extraction Selectivity from Deodorizer Distillate

Mar 19, 2018 - To enhance the extraction selectivity of vitamin E (VE) from the deodorizer distillate, a biphasic system with solvents of both organic...
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Research Article Cite This: ACS Sustainable Chem. Eng. XXXX, XXX, XXX−XXX

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Enhanced Vitamin E Extraction Selectivity from Deodorizer Distillate by a Biphasic System: A COSMO-RS and Experimental Study Hongye Cheng, Jiangsheng Li, Jingwen Wang, Lifang Chen, and Zhiwen Qi* Max Planck Partner Group at the State Key Laboratory of Chemical Engineering, School of Chemical Engineering, East China University of Science and Technology, 130 Meilong Road, Shanghai 200237, China ABSTRACT: To enhance the extraction selectivity of vitamin E (VE) from the deodorizer distillate, a biphasic system with solvents of both organic chemical and the salt tetrabutylammonium chloride ([N4,4,4,4]Cl) was established. The organic solvent was tailored to extract the major component of deodorizer distillate (methyl linoleate), while the organic salt was designed to selectively extract VE by in situ forming a deep eutectic solvent. Three types of organic solvents, namely, ester, arene, and alkane, were analyzed by using the COSMO-RS model, and hexane, exhibiting stronger interaction with methyl linoleate and lower solubility of [N4,4,4,4]Cl, was screened and its suitability explained from the σprofile and σ-potential points of view. The biphasic experiments demonstrated that the selectivity of VE by the one-pass extraction process was significantly enhanced by the biphasic system, and the important operation parameters of the dosage of solvent and initial concentration of VE were analyzed. KEYWORDS: Vitamin E, Deodorizer distillate, Biphasic system, Extraction, Deep eutectic solvent

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INTRODUCTION As an important fat-soluble antioxidant, vitamin E (VE) is widely applied in life-related products, such as cosmetic, medicine, and foods, and natural VE has attracted much more attention than synthetic because of its superiority in dietary safety and biological activity.1 In the natural VE source of methylated oil deodorizer distillate (MODD), there are mainly two compounds, namely, fatty acid methyl ester (FAME) and VE,2 where VE exists as four isomeric molecular structures and its concentration ranges from 2% to 20%. The present industrial method to recover VE from MODD mainly relies on molecular distillation with severe operating conditions (high temperature and high vacuum), which give rise to an increase of investment and energy consumption.3,4 In contrast to molecular distillation, solvent extraction becomes a promising approach to recover VE due to its mild operating conditions. The key to extraction operation is the selection of a suitable solvent.5,6 For VE recovery, α-tocopherol and methyl linoleate, representing VE and FAME, respectively, were commonly selected as the model MODD and employed to evaluate the performance of new extractant or adsorbent for VE separation.7−10 By using this model MODD, Ren and coworkers found that the imidazolium IL with amino acid anion had a strong interaction with α-tocopherol and that the selectivity of α-tocopherol to methyl linoleate can reach up to 29.6.7 As an innovative solvent and analogues of ionic liquid, deep eutectic solvent (DES) becomes more attractive in solvent extraction.11,12 DES is generally formed by combining an © XXXX American Chemical Society

organic salt and a complexing agent, which has a melting point lower than that of each individual component.13 There are two approaches to utilize DES in the VE recovery process. One is to use the ready DES as the extractant solvent to recover VE. For instance, Abdul Hadi et al. successfully applied a choline-based DES to recover the tocopherol from crude palm oil, but its extraction ratio of 1.08% is extremely low.14 Another method is to employ an organic salt to in situ form DES with VE. Qin et al. invented a new process to selectively separate VE from methyl linoleate by in situ forming DES with tetrabutylammonium chloride ([N4,4,4,4]Cl) via hydrogen bonding.15 The extraction ratio of VE dramatically reached up to 90%. However, some amount of methyl linoleate was simultaneously extracted into the formed DES phase, requiring much complex downstream treatment of five-stage cross-current re-extraction to obtain the VE product. Therefore, it is essential to improve the selectivity of VE in a one-step extraction operation. To improve the selectivity to VE over methyl linoleate, a biphasic extraction system with solvents of both organic chemical and salt is an effective way.16 VE (α-tocopherol) with a phenolic −OH group is a weak hydrogen-bond (HB) donor, while methyl linoleate is a weak HB acceptor. In order to highly separate VE and methyl linoleate in a biphasic system, the organic salt should selectively extract the VE by in situ Received: January 29, 2018 Revised: March 15, 2018 Published: March 19, 2018 A

DOI: 10.1021/acssuschemeng.8b00474 ACS Sustainable Chem. Eng. XXXX, XXX, XXX−XXX

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ACS Sustainable Chemistry & Engineering

and 1,4-dimethylbenzene, and ethylbenzene), and alkane (pentane, hexane, heptane, and octane), were considered in the COSMO-RS calculation.

forming DES via hydrogen bonding, while the organic solvent should be favorable for the extraction of methyl linoleate from VE.16,17 The formation of DES with VE by the addition of [N4,4,4,4]Cl was investigated in our previous work,15 which exhibited excellent performance for VE recovery. Therefore, the selection of organic solvent was focused in this work by considering two aspects. Strong interaction of the organic solvent with methyl linoleate can reduce the residual content of methyl linoleate in the formed DES phase and consequently improve the selectivity of VE.18−21 Moreover, the low solubility of [N4,4,4,4]Cl in the organic solvent is required for biphasic extraction. From contributions of the molecular interaction and solubility prediction by using COSMO-RS,22−25 this model is quite suitable for predicting the nonideal liquid-phase behavior based on molecular interactions. In this work, three types of organic solvents, including the ester, arene, and alkane, were evaluated by using COSMO-RS with respect to their interactions with methyl linoleate and their abilities of dissolving the organic salt [N4,4,4,4]Cl. The biphasic extraction and solubility experiments were then carried out to verify COSMO-RS predictions.

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PREDICTION AND EXPERIMENTAL METHODS COSMO-RS Calculation. COSMO-RS is a fully predictive model that relies only on molecular information and does not require any experimental data.26,27 The calculation of molecular interaction and the prediction of solubility using COSMO-RS is helpful for screening the most suitable organic solvent.18,19 The COSMO-RS calculations were performed using COSMOthermX (COSMOlogic GmbH & Co. KG, Version C3.0, Release 14.01) at the BP86/TZVP level with the parameter file BP_TZVP_C30_1401.ctd. The .cosmo files of all compounds involved in this work were taken from the database.28,29 On the basis of the .cosmo files, the software can apply statistical thermodynamic principles to compute the molecular energy, including the electrostatic misfit, hydrogen bond (HB), and van der Waals interactions. The electrostatics (Emisfit) and hydrogen bonding (EHB) are described as functions of the polarization charges of two interacting surface segments σ and σ′ or σacceptor and σdonor, if the segments are located on a hydrogen bond donor or acceptor atom. The less-specific van der Waals (EvdW) interactions are taken into account in a slightly more approximate way. Emisfit(σ ,σ ′) = aeff

α′ (σ + σ ′) 2

(1)

E HB = aeff c HB min[(0;min(0;σdonor + σHB) max(0;σacceptor − σHB)] ′ ) EvdW = aeff (τvdW + τvdW

EXPERIMENTS

Chemicals. Methyl linoleate (≥99%) and α-tocopherol (≥96%) were purchased from Acros and Tci, respectively. Tetrabutylammonium chloride ([N4,4,4,4]Cl) was obtained from Adamas with a purity of ≥98%. The organic salts were treated by vacuum-drying under 2 kPa and at 80 °C for 24 h to ensure the low water content ( arene > ester, as illustrated in Figure 1b. Moreover, their strong interaction signifies that methyl linoleate prefers to distribute in the solvent phase rather than the DES phase. To verify the result predicted from the analysis of COSMORS interaction, biphasic extraction experiments were carried out. Seven organic solvents, including n-propyl acetate, dimethyl carbonate, toluene, ethylbenzene, n-hexane, nheptane, and n-octane, were selected as the typical ester, arene, and alkane, respectively. As demonstrated in Figure 2, βMe in two phases (DES phase and solvent phase) varies and follows the sequence of alkane < arene < ester. It should be noted that, as defined in eq 4, a smaller value of βMe indicates that methyl linoleate is more likely to distribute in the solvent phase, which is more favorable for biphasic extraction. Therefore, the experimental result agreed well with the interaction analysis by COSMO-RS; i.e., alkane had a stronger interaction with methyl linoleate and hence had a small partition coefficient of methyl linoleate. As a result, alkane is more promising to be employed as the solvent phase in the biphasic extraction.

Figure 1. COSMO-RS interaction energies between organic solvents and methyl linoleate. (a) Misfit and van der Waals interaction energies. (b) Total interaction energy.

On the Basis of the Solubility of [N4,4,4,4]Cl in Organic Solvent. For the extraction in a biphasic system, it is important that the solubility of the organic salt [N4,4,4,4]Cl in the organic solvent should be as low as possible, in order to reduce the loss and contamination of the organic solvent phase. Hence, the solubility of [N4,4,4,4]Cl in organic solvents was evaluated by employing the COSMO-RS model for the same solvents in the interaction calculation. As shown in Figure 3, as a higher value implies a larger solubility of [N4,4,4,4]Cl in the organic solvent, ester and arene have a better solubility of [N4,4,4,4]Cl than C

DOI: 10.1021/acssuschemeng.8b00474 ACS Sustainable Chem. Eng. XXXX, XXX, XXX−XXX

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Figure 4. Solubility of [N4,4,4,4]Cl in toluene and hexane at different temperatures. Figure 2. Partition coefficient of methyl linoleate in a biphasic system with different organic solvents.

operation of the organic solvent, a lower boiling point is desirable. By comparing the boiling points of pentane (36 °C), hexane (69 °C), heptane (98 °C), and octane (126 °C), hexane, with a lower boiling point than heptane and octane but higher than the extraction temperature (55 °C), is preferable, and its performance in the biphasic extraction for VE purification was further investigated. Molecular Interaction Analysis. The performance of organic solvents can be explained from the molecular interactions with the help of σ-profile and σ-potential. In COSMO-RS theory, the σ-profile obtained from quantum chemical calculations is one of the most important moleculespecific properties.26,34,35 According to the distribution of the screening charge density (σ) of the molecule, the σ-profile is divided into three regions, namely, nonpolar (−0.0084 e/Å2 < σ < 0.0084 e/Å2), hydrogen-bond acceptor (HBA, σ > 0.0084 e/Å2), and hydrogen-bond donor (HBD, σ < −0.0084 e/Å2).36 Moreover, the σ-potential can be used to evaluate the affinity of a component toward another in a mixture. In general, the more negative value of σ-potential suggests the stronger affinity of the solvent to a molecular surface of polarity σ, while a higher positive value indicates an increase in repulsive behavior. Similar to the σ-profile plot, there are three regions divided by the HB threshold (σhb = ±0.0084 e/Å2). The σ-profile and σ-potential for methyl linoleate, hexane, toluene, dimethyl carbonate, and [N4,4,4,4]Cl are plotted in Figures 5 and 6, respectively. From Figure 5, the σ-profile of methyl linoleate is mainly distributed in the nonpolar region with a large peak arising from the long alkyl chain in methyl linoleate. A small peak in the HBA region is assigned to the O atoms in methyl linoleate, indicating its weak HBA ability. Moreover, from Figure 6, for the σ-potential of methyl linoleate, its negative value in the nonpolar region indicates a strong affinity toward a nonpolar surface; meanwhile, its negative value in the HBD region but positive value in the HBA region suggest its weak affinity for HBD but repulsive interaction with HBA. For the σ-profile of organic salt [N4,4,4,4]Cl, the peak distributed within the range of −0.012 e/Å2 < σ < 0.005 e/ Å2 is assigned to the cation of [N4,4,4,4]+, and the peak at around 0.019 e/Å2 is ascribed to the anion of Cl−, suggesting its strong HBA ability but weak HBD ability. This is also reflected in the σ-potential of [N4,4,4,4]Cl, where the negative value in the

Figure 3. COSMO-RS-predicted solubility of [N4,4,4,4]Cl in different organic solvents at various temperatures.

alkane, and this solubility is enhanced by increasing the temperature. To validate the predicted solubility of [N4,4,4,4]Cl, experiments were carried out with hexane, toluene, and dimethyl carbonate representing the typical alkane, arene, and ester, respectively. In good agreement with the COSMO-RS prediction, the experimental solubility of [N4,4,4,4]Cl in the solvent phase is ordered as hexane < toluene < dimethyl carbonate. For instance, at 30 °C, the solubility of [N4,4,4,4]Cl in dimethyl carbonate is 675 g/L, which is several orders of magnitude higher than that in toluene (1376 mg/L) and hexane (23 mg/L). Moreover, similar to the COSMO-RS prediction, experimental solubility also increases with the temperature. From Figure 4, the solubility of [N4,4,4,4]Cl in toluene varies from 1376 to 1904 mg/L when increasing the temperature from 30 to 55 °C. In contrast, the solubility of [N4,4,4,4]Cl in hexane is extremely low and only ranges from 23 to 123 mg/L. On the basis of the comparison of the interaction with methyl linoleate and the solubility of [N4,4,4,4]Cl, alkane is the most suitable organic solvent to act as the solvent phase in the biphasic extraction. Moreover, considering the recovery D

DOI: 10.1021/acssuschemeng.8b00474 ACS Sustainable Chem. Eng. XXXX, XXX, XXX−XXX

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Moreover, both toluene and hexane demonstrate parabolic curves of their σ-potential and positive value outside the HB threshold, implying their repulsive interactions with HB donor and acceptor. However, hexane exhibits stronger repulsive ability than toluene due to its higher values in the HB region. The above features of hexane give rise to a strong interaction with methyl linoleate but a repulsive interaction with [N4,4,4,4] Cl and consequently a low solubility of [N4,4,4,4]Cl. Intensified VE Selectivity via Biphasic Extraction. In order to validate the intensified extraction selectivity to VE of the biphasic system with hexane as the solvent phase, the model oil consisting of methyl linoleate and α-tocopherol was employed. The effects of the dosage of hexane and the initial concentration of α-tocopherol in model oil were studied. Influence of the Dosage of Hexane. The dosage of hexane was characterized by the mass ratio of hexane to [N4,4,4,4]Cl, which ranges from 0 to 2.0 in this work. The ratio 0 refers to the case of the only associative extraction by in situ forming DES in our previous work.17 As seen in Figure 7a, when

Figure 5. σ-Profile of methyl linoleate, [N4,4,4,4]Cl, dimethyl carbonate, toluene, and hexane. Vertical dashed lines represent the threshold value for the hydrogen-bond interaction (σhb = ±0.0084 e/Å2).

Figure 6. σ-Potential of methyl linoleate, [N4,4,4,4]Cl, dimethyl carbonate, toluene, and hexane. Vertical dashed lines represent the threshold value for the hydrogen-bond interaction (σhb = ±0.0084 e/ Å2).

nonpolar region and much stronger negative value in the HBD region but positive value in HBA region indicate its affinity and attractive interaction for nonpolar molecule and HBD but repulsive interaction with HBA. These interactions result in the weak HBA of methyl linoleate, it being partially extracted into the DES phase. For dimethyl carbonate, the σ-profile exhibits a strong peak distributed at the negative coordinate of the nonpolar region and a small peak at 0.013 e/Å2 of the HBA region. Its similar features of σ-profile and σ-potential to methyl linoleate give rise to a strong repulsive electrostatic interaction with methyl linoleate. Moreover, the complementary σ-profiles of [N4,4,4,4] Cl and dimethyl carbonate lead to the interaction of the cation of [N4,4,4,4]+ and anion Cl− with the O and H atoms of dimethyl carbonate, respectively. These interactions lead to a high solubility of [N4,4,4,4]Cl in dimethyl carbonate. Comparing with toluene, the σ-profile of hexane is more narrowly distributed around 0 e/Å2 only inside the nonpolar region, signifying the stronger nonpolar property of hexane.

Figure 7. Effect of hexane dosage on biphasic extraction performance. (a) Partition coefficients of α-tocopherol (βα) and methyl linoleate (βMe) and selectivity of α-tocopherol (S). (b) Extraction ratio of αtocopherol (η).

increasing the dosage of hexane from 0 to 2.0, the partition coefficient of α-tocopherol (βα) increases from 2.97 to 5.25, while the partition coefficient of methyl linoleate (βMe) decreases from 0.10 to 0.07. According to the definition, high βα and low βMe are favorable for improving the selectivity to αtocopherol (Sα). As a consequence, Sα is dramatically enhanced E

DOI: 10.1021/acssuschemeng.8b00474 ACS Sustainable Chem. Eng. XXXX, XXX, XXX−XXX

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Furthermore, the concentration of α-tocopherol and methyl linoleate in the DES phase is analyzed individually (Figure 8b). When increasing the dosage of hexane, the concentration of methyl linoleate is significantly reduced from 9.76% to 1.43% while it declines from 3.89% to 3.20% for α-tocopherol, which are about 85.3% and 17.7% reduction comparing to the case of only in situ associative extraction. Thus, the significant reduction of the methyl linoleate concentration in the DES phase and consequently the huge increment of the concentration ratio of α-tocopherol to methyl linoleate in the DES phase is the main reason for the enhancement of selectivity to α-tocopherol. Influence of Initial Concentration of α-Tocopherol in Model Oil. As the concentration of VE varies with the sources, the influences of the initial concentration of α-tocopherol in model oil on the partition coefficient, selectivity, and extraction ratio of α-tocopherol were investigated. As illustrated in Figure 9, with increasing the concentration of α-tocopherol from 2%

from 30.0 to 74.6, indicating an intensified purification of VE in the biphasic extraction with hexane as the solvent phase. From Figure 7b, the extraction ratio is slightly reduced from 88.9% to 71.5%, which is ascribed to the reduction of the content of αtocopherol in the DES phase from 3.89% to 3.20%, as illustrated in Figure 8.

Figure 8. Effect of hexane dosage on (a) the mass concentration ratio of α-tocopherol to methyl linoleate (xα/xMe) in DES and solvent phase and (b) the mass concentration of α-tocopherol and methyl linoleate in DES phase.

To better understand the enhancement of selectivity in detail, the equation of selectivity to α-tocopherol is transformed from eq 5 into eq 7. The numerator represents the concentration ratio of α-tocopherol to methyl linoleate in the DES phase, while the denominator is their concentration ratio in the solvent phase. Sα = βα /βMe =

(xαDES/xαsolvent) DES solvent (xMe /xMe )

=

Figure 9. Effect of initial mass concentration of α-tocopherol in model oil on biphasic extraction performance. (a) Partition coefficients of αtocopherol (βα) and methyl linoleate (βMe) and selectivity of αtocopherol (S). (b) Extraction ratio of α-tocopherol (η).

DES (xαDES/xMe ) solvent (xαsolvent /xMe )

(7)

to 18%, βα decreases first from 4.14 to 2.98 and then increases to 4.56, while βMe declines from 0.15 to 0.08 and then changes slightly. As a consequence, the selectivity to α-tocopherol increases gradually from 27.8 to 53.1, and the extraction ratio of α-tocopherol rose from 67.6% to 91.2%. Both the selectivity and extraction ratio of α-tocopherol are improved with the increase of the initial concentration of α-tocopherol in model

The variation of the concentration ratio of α-tocopherol to methyl linoleate in two phases are illustrated in Figure 8a. Upon increasing the dosage of hexane, the concentration ratio in the DES phase increases significantly from 0.40 to 2.24, about 5.6 times of the case of only in situ associative extraction. On the contrary, the concentration ratio in the organic solvent phase increases in a slight increment from 0.013 to 0.03. F

DOI: 10.1021/acssuschemeng.8b00474 ACS Sustainable Chem. Eng. XXXX, XXX, XXX−XXX

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extraction from deodorizer distillate. ACS Sustainable Chem. Eng. 2016, 4, 583−590. (10) Qin, L.; Zeng, Q.; Zhang, J. J.; Cheng, H. Y.; Chen, L. F.; Qi, Z. W. Integrated process for extracting vitamin E with high purity from the methylated oil deodorizer distillate. Sep. Purif. Technol. 2018, 196, 229−236. (11) Abbott, A. P.; Boothby, D.; Capper, G.; Davies, D. L.; Rasheed, R. K. Deep eutectic solvents formed between choline chloride and carboxylic acids: versatile alternatives to ionic liquids. J. Am. Chem. Soc. 2004, 126, 9142−9147. (12) Abbott, A. P.; Capper, G.; Davies, D. L.; Rasheed, R. K.; Tambyrajah, V. Novel solvent properties of choline chloride/urea mixtures. Chem. Commun. 2003, 0, 70−71. (13) Paiva, A.; Craveiro, R.; Aroso, I.; Martins, M.; Reis, R. L.; Duarte, A. R. C. Natural deep eutectic solvents − solvents for the 21st century. ACS Sustainable Chem. Eng. 2014, 2, 1063−1071. (14) Abdul Hadi, N.; Ng, M. H.; Choo, Y. M.; Hashim, M. A.; Jayakumar, N. S. Performance of choline-based deep eutectic solvents in the extraction of tocols from crude palm oil. J. Am. Oil Chem. Soc. 2015, 92, 1709−1716. (15) Qin, L.; Li, J. S.; Cheng, H. Y.; Chen, L. F.; Qi, Z. W.; Yuan, W. K. Association extraction for vitamin E recovery from deodorizer distillate by in situ formation of deep eutectic solvent. AIChE J. 2017, 63, 2212−2220. (16) Cao, Y. F.; Xing, H. B.; Yang, Q. W.; Li, Z. K.; Chen, T.; Bao, Z. B.; Ren, Q. L. Biphasic systems that consist of hydrophilic ionic liquid, water, and ethyl acetate: the effects of interactions on the phase behavior. Ind. Eng. Chem. Res. 2014, 53, 10784−10790. (17) Santos, J. H. P. M.; Flores-Santos, J. C.; Meneguetti, G. P.; Rangel-Yagui, C. O.; Coutinho, J. A. P.; Vitolo, M.; Ventura, S. P. M.; Pessoa, A. In situ purification of periplasmatic L-asparaginase by aqueous two phase systems with ionic liquids (ILs) as adjuvants. J. Chem. Technol. Biotechnol. 2017, DOI: 10.1002/jctb.5455. (18) Lei, Z. G.; Chen, B. H.; Li, C. Y. COSMO-RS modeling on the extraction of stimulant drugs from urine sample by the double actions of supercritical carbon dioxide and ionic liquid. Chem. Eng. Sci. 2007, 62, 3940−3950. (19) Lei, Z. G.; Arlt, W. G.; Wasserscheid, P. Selection of entrainers in the 1-hexene/n-hexane system with a limited solubility. Fluid Phase Equilib. 2007, 260, 29−35. (20) Li, H. P.; Zhang, B. B.; Jiang, W.; Zhu, W. S.; Zhang, M.; Wang, C.; Pang, J. Y.; Li, H. M. A comparative study of the extractive desulfurization mechanism by Cu(II) and Zn-based imidazolium ionic liquids. Green Energy Environ. 2017, DOI: 10.1016/j.gee.2017.10.003. (21) Bai, Y.; Yan, R.; Tu, W. H.; Qian, J. G.; Gao, H. S.; Zhang, X. P.; Zhang, S. J. Selective separation of methacrylic acid and acetic acid from aqueous solution using carboxyl-functionalized ionic liquids. ACS Sustainable Chem. Eng. 2018, 6, 1215−1224. (22) Song, Z.; Zeng, Q.; Zhang, J. N.; Cheng, H. Y.; Chen, L. F.; Qi, Z. W. Solubility of imidazolium-based ionic liquids in model fuel hydrocarbons: a COSMO-RS and experimental study. J. Mol. Liq. 2016, 224, 544−550. (23) Hizaddin, H. F.; Hadj-Kali, M. K.; Ramalingam, A.; Hashim, M. A. Extractive denitrogenation of diesel fuel using ammonium- and phosphonium-based deep eutectic solvents. J. Chem. Thermodyn. 2016, 95, 164−173. (24) Zhou, T.; Chen, L.; Ye, Y. M.; Chen, L. F.; Qi, Z. W.; Freund, H.; Sundmacher, K. An overview of mutual solubility of ionic liquids and water predicted by COSMO-RS. Ind. Eng. Chem. Res. 2012, 51, 6256−6264. (25) Song, Z.; Zhou, T.; Zhang, J. N.; Cheng, H. Y.; Chen, L. F.; Qi, Z. W. Screening of ionic liquids for solvent-sensitive extraction - with deep desulfurization as an example. Chem. Eng. Sci. 2015, 129, 69−77. (26) Cheng, H. Y.; Liu, C. Y.; Zhang, J. J.; Chen, L. F.; Zhang, B. J.; Qi, Z. W. Screening deep eutectic solvents for extractive desulfurization of fuel based on COSMO-RS model. Chem. Eng. Process. 2018, 125, 246−252. (27) Salleh, Z.; Wazeer, I.; Mulyono, S.; El-blidi, L.; Hashim, M. A.; Hadj-Kali, M. K. Efficient removal of benzene from cyclohexane-

oil. Therefore, the high content of VE in oil can promote the purification of VE.

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CONCLUSION To intensify the selectivity of VE by a biphasic extraction system, three types of organic solvents, including ester, arene, and alkane, were evaluated by using COSMO-RS theory with respect to their interactions with methyl linoleate and the solubility of [N4,4,4,4]Cl. The predicted COSMO-RS interaction and solubility qualitatively agree well with experimental results. Alkane, which can build stronger interaction with methyl linoleate and dissolve less [N4,4,4,4]Cl, was selected to form the biphasic system. The analyses of σ-profile and σ-potential declare that the nonpolar nature of hexane gives rise to its strong interaction with methyl linoleate and low solubility of [N4,4,4,4]Cl. The intensified extraction selectivity to VE of the biphasic system with hexane as the solvent was validated experimentally and the selectivity to VE was improved with the dosage of hexane and the initial concentration of VE in oil.

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AUTHOR INFORMATION

Corresponding Author

*E-mail: [email protected]. ORCID

Zhiwen Qi: 0000-0003-2037-2234 Notes

The authors declare no competing financial interest.

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ACKNOWLEDGMENTS The financial support from National Natural Science Foundation of China (21776074), Shanghai Committee of Science and Technology (16dz1206203), and 111 Project (B08021) is greatly acknowledged.

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DOI: 10.1021/acssuschemeng.8b00474 ACS Sustainable Chem. Eng. XXXX, XXX, XXX−XXX

Research Article

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DOI: 10.1021/acssuschemeng.8b00474 ACS Sustainable Chem. Eng. XXXX, XXX, XXX−XXX