Natural deep eutectic solvents (NADES) may be considered ‘designer solvents’ due to their numerous structural variations and the possibility of tailoring their physicochemical properties. Prior to their industrial application, characterization of NADES is essential, including determination of their physicochemical properties, cytotoxicity, and antioxidative activity. The most important physicochemical properties of eight prepared NADES (choline chloride:malic acid, proline:malic acid, choline chloride:proline:malic acid, betaine:malic acid, malic acid:glucose, malic acid:glucose:glycerol, choline chloride:citric acid, and betaine:citric acid) were measured as functions of temperature and water content. In general, the structure of prepared NADES greatly influences their physical properties, which could be successfully modified and adjusted by addition of water. All tested NADES were absolutely benign and noncorrosive for investigated steel X6CrNiTi18-10. Furthermore, cytotoxicity of prepared solvents was assessed toward three human cell lines (HEK-293T, HeLa, and MCF-7 cells), and antioxidative activity was measured by the Oxygen Radical Absorbance Capacity (ORAC) method. With regard to cell viability, all tested NADES containing carboxylic acid could be classified as practically harmless and considered environmentally safe. The ORAC values indicated that the tested NADES displayed antioxidative activity.

BACKGROUND Deep eutectic solvents (DESs) are being used in different applications as replacements for classical organic solvents; their physico‐chemical properties comply with the criteria of environmental acceptability. RESULTS In this work, choline chloride‐glycerol based DESs of different molar ratios (ChCl‐Gly 1:1.5, 1:2 and 1:3) were prepared and characterized with respect to density, dynamic viscosity, refractive index, electrical conductivity and thermal properties. The DESs were tested for denitrification, desulfurization and dearomatization of the six‐component model gasoline composed of three aliphatic hydrocarbons and pyridine, thiophene and toluene as representatives of nitrogen, sulfur and aromatic compounds of fuel, respectively. It was found that ChCl‐Gly is a better solvent for removal of pyridine from model gasoline in comparison with thiophene and toluene. Optimally, denitrification efficiency of 58% can be achieved in one‐stage extraction, and deep denitrification can be achieved in five‐stage extraction resulting in an efficiency of 99.62%. By performing a four‐stage extraction using the same batch of DES, a gradual decrease in extraction efficiency was observed. By evaporative purification of DES between the stages, the extraction efficiency was found to remain constant. ChCl‐Gly exhibited significant efficiency in denitrification of fluid catalytic cracking gasoline as well. CONCLUSION ChCl‐Gly based DESs are suitable for denitrification of fuel. The ability of application environmentally friendly solvents in the fuel purification process contributes to the development of cleaner technologies. © 2018 Society of Chemical Industry

Deep eutectic solvents (DES), a class of 'green' solvents, are being tested for extractive desulfurization, denitrification and dearomatization of fuels. Here, three DESs were prepared by combining betaine (B) with glycerol (Gly), ethylene glycol (EG) or propylene glycol (PG) in the molar ratios of 1:3, 1:3 and 1:3.5, respectively. The DESs were used for the removal of thiophene, pyridine and toluene from a 6-component model gasoline and for the removal of sulfur and nitrogen compounds from a real fluid catalytic cracking (FCC) gasoline. Physical properties of the prepared DESs -density, viscosity, refractive index, specific conductance, thermal conductivity, temperature diffusivity and heat capacity were determined, too. All tested DESs exhibit higher potential for denitrification of model fuel with respect to desulfurization and dearomatization. B-PG 1:3.5 worked best in one-stage denitrification of both model gasoline (∼ 80%) and real FCC gasoline (∼ 36%). The reuse of solvent without loss in extraction efficiency in four extraction stages was successfully achieved for all three DESs by evaporation purification of DES between the stages.

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