Effect of Metal-Containing Anions on the Catalytic Properties of Imidazolium Derivatives Immobilized on Silochrome in Oxidative Desulfurization

A comparative analysis is performed for the properties of two Fenton-type catalysts in the oxidation of sulfur-containing compounds with hydrogen peroxide and the desulfurization of crude oil. The catalysts are based on Cu(I) and Fe(III), and Mo(VI) and W(VI) polyoxometalates. Heterogeneous samples are imidazolium salts chemically immobilized on surfaces of silochrome and contain the iron and copper chloride complexes or phosphomolybdic and phosphotungstic acid anions. Thiophene (T), dibenzothiophene (DBT), methylphenyl sulfide (MPS), and a diesel fraction with an initial amount of sulfur of 1080 ppm are used as model substrates. It is found that the order of reactivity of thiophene substrates depends on the nature of metal-containing anions: thiophene > DBT on the Cu and Fe catalysts and DBT > thiophene on the polyoxometalate catalysts. This effect is explained using literature data. The catalyst based on phosphotungstic acid allows desulfurization of the diesel fraction of oil to amounts of sulfur of < 10 ppm, which meets today’s environmental standards.