The tightening of environmental regulations aimed at minimizing emissions of harmful nitrogen and sulfur oxides requires the development of effective methods for deep purification of petroleum products from heterocyclic compounds. Despite the prospect of eutectic solvents as an environmentally friendly alternative to traditional extractants in denitrification and desulfurization processes, their industrial implementation is hindered by technologically unsuitable physical and chemical properties and insufficient extraction efficiency for a number of components. In this work a new hydrofilic eutectic solvent based on polyethylene glycol methyl ether with molecular weight 350 (PEG ME-350) and tetrabutylammonium bromide (TBAB) was proposed. The eutectic solvent shows favorable physicochemical properties for extraction processes: low viscosity of 68.1 mPa·s and high density of 1.08 g/cm at ambient conditions. In comparison with industrial N-methylpyrrolidone, the use of the new eutectic solvent leads to a statistically significant increase in the extraction yield of heterocyclic compounds: the increase is 78.8, 6.4, 8.7 and 13.9% for thiophene, indole, quinoline and pyridine, respectively. The extraction process is characterized by a high rate of reaching thermodynamic equilibrium (within 1 min). The optimum volume ratio of extractant/raw material phases is 1 : 1. The extraction efficiency does not depend on temperature in the investigated range, which allows the process to be carried out efficiently at 25°C. The constancy of distribution coefficients in the system for all organic compounds in wide range of their initial concentrations is observed, which is especially important for scaling of chemical-technological processes.
Lobovich et al. (Wed,) studied this question.