N-METHYLPYRROLIDONE – SELECTIVE SOLVENT FOR OXIDATIVE DESULFURIZATION OF LIGHT GASOLINE FRACTIONS

Abstract

The extraction of various sulfur-containing compounds occurring in the oil and condensate fractions using solutions based on N-methylpyrrolidone was studied. The extracts can later be used in the organic/electrochemical synthesis of valuable organosulfur compounds. By the example of a model mixture, the solvent is shown to be selective to various classes of organic sulfur compounds: thiols, mono-, di-, and trisulfides. It is established that the solvent exhibits the greatest affinity to aromatic sulfur compounds. The extraction degree increases from mono- to di- and trisulfide. In the case of aliphatic thiols, a decrease in the degree of extraction is observed with an increase in the length of the hydrocarbon group. The optimal parameters of extraction with mixtures based on N-methylpyrrolidone for light gasoline fractions BPT-90 °C and BPT-120 °C were set: the temperature – 35 °C, the ratio solvent - feedstock is 1 to 1. In the series of different mixtures of solvents, a selective solvent based on dimethyl carbonate (5% by weight) showed the highest efficiency. At the same time, the highest raffinate yield with a moderate total sulfur content is observed for the solvent with H2O (5% by weight). A multi-stage extraction of sulfur components from gasoline fractions using the mixture N-methylpyrrolidone with H2O allowed reducing the content of organic sulfur compounds by 7-10 times. A combined process based on the extraction of thiols from model mixtures and its oxidation by o-benzoquinones is proposed. Unlike the more aggressive oxidizing agents o-benzoquinones depending on the structure ensure the utilization of thiols to thioethers or disulfides.