Ternary liquid–liquid equilibrium data for n-Hexane-Benzene-DES (choline chloride/ethylene glycol, choline chloride/glycerol, choline chloride/urea) at 303 K and 101.3 kPa

Deep Eutectic Solvents as Suitable Solvents for Lipase-Catalyzed Transesterification Reactions

In this work, three deep eutectic mixtures (DES 1: choline chloride/urea; DES 2: choline chloride/glycerol; and DES 3: tetrabutylammonium bromide/imidazole) were investigated as mediums for the synthesis of glucose laurate and glucose acetate. Aiming to achieve a greener and more sustainable approach, the synthesis reactions were catalyzed by lipases from Aspergillus oryzae (LAO), Candida rugosa (LCR), and porcine pancreas (LPP). The hydrolytic activity of lipases against p-nitrophenyl hexanoate revealed no evidence of enzyme inactivation when DES were used as medium. Regarding the transesterification reactions, combining LAO or LCR with DES 3 resulted in the efficient production of glucose laurate (from glucose and vinyl laurate) (conversion >60 %). The best result for LPP was observed in DES 2, with 98 % of product production after 24 hours of reaction. When replacing vinyl laurate by a smaller hydrophilic substrate, vinyl acetate, a distinct behavior was observed. LCR and LPP performed better in DES 1, yielding more than 80 % of glucose acetate after 48 hours of reaction. The catalytic activity of LAO was less pronounced, reaching only nearly 40 % of product in DES 3. The results highlight the potential of combining biocatalysis with greener and environmentally-safer solvents, for the synthesis of differentiated chain-length sugar fatty acid esters (SFAE).

Evaluation of hybrid solvents featuring choline chloride-based deep eutectic solvents and ethanol as extractants for the liquid-liquid extraction of benzene from n-hexane: towards a green and sustainable paradigm

Deep eutectic solvents (DESs) have high viscosities, but known to be mitigated by addition of suitable co-solvent. The effect of such co-solvent on the extraction efficiency of the hybrid solvent is hardly known. This study examined the effect of ethanol on three choline chloride-based DESs (glyceline, reline, and ethaline) by mixing each in turn with ethanol in various volume proportions. The hybrid solvents were evaluated for the extraction of benzene from n-hexane. Pseudo-ternary liquid–liquid equilibrium data were obtained using the refractive index method at 303 K and 1 atm for the systems, n-hexane (1) + benzene (2) + hybrid solvent (glyceline/ethanol, ethaline/ethanol, reline/ethanol) (3), and used to evaluate distribution coefficient (D) and selectivity (S). Furthermore, the physicochemical properties of the hybrid solvents were also determined. The results indicate increase in selectivity with increasing ethanol addition up to 50% and decrease with further addition. All hybrid solvents with 50% ethanol outperform sulfolane and are suitable replacement for same as green and sustainable extractant for aromatics from aliphatics. The glyceline + 50% ethanol emerged the overall best with 49.73% elevation in selectivity and 41.15% reduction in viscosity relative to the neat glyceline. The finding of this study is expected to fillip the drive for paradigm shift in petrochemical industries.

Binary mixtures of choline chloride-based deep eutectic solvents as green extractants for the extraction of benzene from n-hexane

A suitable green solvent for extraction of aromatics from aliphatics must possess good solvation and physicochemical properties, a rare occurrence in a single deep eutectic solvent (DES). Mixture of DESs could enable synergy and provide a good candidate extractant. In this study, DESs of glyceline, ethaline, and reline were synthesized and their binary mixtures (glyceline/ethaline, reline/ethaline, and glyceline/reline) produced by blending in various volume proportions. Twelve of such mixed solvents were prepared and their extraction efficiency for separating benzene from n-hexane investigated in a batch equilibrium process. Liquid–liquid equilibria (LLE) data for the pseudo-ternary systems of n-hexane + benzene + mixed DESs were measured at 303 K and 101.3 kPa. The distribution coefficient (D) and selectivity (S) of each pseudo-ternary system were determined to elicit extraction efficiency. The physicochemical properties of the mixed DESs were also measured. The results show that generally the distribution coefficients, selectivities, and physicochemical properties of the mixed DESs lie between the corresponding values for the constituent DES. The best performance was given by the mixed solvent of glyceline and ethaline in the 80:20 volume ratio, respectively, with D = 0.75 and S = 422.485. This assertion was further corroborated by higher percent recovery of benzene obtained from the said mixed DES (57.88%) relative to other mixed DESs (≤ 49.11%) examined in this study. Furthermore, its separation efficiency is superior to sulfolane but lower than glyceline, though there was a 9.4% reduction in its viscosity relative to glyceline.

ASPEN plus simulation of liquid–liquid equilibria data for the extraction of aromatics from waste tyre pyrolysis gasoline using organic and deep eutectic solvents: a comparative study

Waste tyre pyrolysis gasoline (WTPG) contain significant amount of aromatics such as benzene, toluene and xylenes (BTX) and thus provide a good source for these value-added chemicals. Separation of aromatics from aliphatic media as obtained in WTPG and naphtha is done commercially by solvent extraction using volatile organic solvents such as sulfolane (SUF), dimethylformamide (DMF) and diethylene glycol (DEG). The high cost of this state-of-the art separation method and environmental consideration have necessitated search for non-volatile and green solvent such as deep eutectic solvent (DES). This study intends to conduct a comparative evaluation of the performance of five solvents (SUF, DMF, DEG, and two DESs) for the extraction of BTX from WTPG. The two DESs are choline chloride/ethylene glycol (DES1) and choline chloride/glycerol (DES2) in molar ratios 1:2. An ASPEN plus simulation was carried out to generate liquid–liquid equilibria (LLE) data for the pseudo-ternary systems {WTPG + BTX + solvent (SUF/DMF/DEG/DES)}. Performance evaluation was based on selectivity (S) and solute (BTX) distribution coefficient (D). The propriety of the simulation protocol was validated using literature data. The results revealed the following maximum values of selectivity and distribution coefficients for the solvents: DES2 (S = 378.283, D = 0.656); DES1 (S = 77.364, D = 1.423); SUF (S = 55.371, D = 0.756); DMF (S = 25.336, D = 0.786) and DEG (S = 17.531, D = 0.793). The DESs therefore performed better than the organic solvents and can suitably replace same in the extraction of BTX from waste tyre pyrolysis gasoline.