Study on the application of imidazole phosphotungstate composite in oxidative desulfurization

This article reports the synthesis of three imidazolium phosphotungstate catalysts using 1-hydroxyimidazole ionic liquids with different substituents as raw materials and ion exchange method. Through dispersion performance testing and oxidative desulfurization experiments, it was found that the dispersion of the catalyst in the system greatly affects the desulfurization efficiency. When using imidazolium phosphotungstate as a catalyst and imidazolium ionic liquid as a solvent, the liquid-solid phase system can be transformed into a liquid-liquid phase system to achieve efficient dispersion of the catalyst in the reaction system. Meanwhile, the effects of reaction time, solvent volume, oxidant dosage, catalyst type, and solvent type on desulfurization efficiency were investigated in the experiment. The results showed that under the conditions of reaction temperature of 30 ℃, solvent oil volume ratio of 1:15, reaction time of 30 min, and oxidant to dibenzothiophene molar ratio of 8:1, the combination of 1-hexyl-3-methylimidazolium phosphotungstate and 1-hexyl-3-methylimidazolium chloride had a good desulfurization effect, with a desulfurization rate of up to 98.3%. After repeated use, the desulfurization rate did not significantly decrease, and the catalyst structure was not damaged. Finally, it was confirmed through liquid chromatography and titration experiments that the main oxidation products were sulfoxides and sulfones, as well as a small amount of sulfates and sulfites, and the reaction mechanism was predicted.