The effect of the nature of metal-containing anions on the catalytic properties of imidazolium derivatives immobilized on silochrom in oxidative desulfurization
Two types of catalysts - Fenton catalysts based on Cu(I) and Fe(III), and polyoxometalates Mo(VI) and W(VI) - were compared in the oxidation of sulfur-containing compounds by hydrogen peroxide and desulfurization of oil stock. Heterogeneous samples were represented by imidazolium salts chemically anchored on the silochrom surface and containing chloride complexes of iron and copper or anions of phosphomolybdic and tungstophosphoric acids. Thiophene (T), dibenzothiophene (DBT) and methyl phenyl sulfide (MPS) as well as the diesel fraction with the initial sulfur content of 1080 ppm were used as the model substrates. The reactivity of thiophene substrates was found to depend on the nature of metal-containing anions: on Cu and Fe catalysts, thiophene > DBT, while on polyoxometalate catalysts, DBT > thiophene. This effect was interpreted using literature data. The catalyst based on tungstophosphoric acid provided desulfurization of the diesel fraction of oil to the sulfur content < 10 ppm, which corresponds to modern environmental standards.