Comparative analysis of heterogeneous catalysts for the peroxide oxidation of thiophene is conducted. The catalysts are imidazole ionic liquids (ILs) containing anions of phosphomolybdic and phosphotungstic acids immobilized on mineral supports. Immobilization is implemented by the covalent bonding of an IL fragment to a silica surface or by adsorption on alumina. The catalysts are active not only in the model oxidation of thiophene in isooctane, but also in the desulfurization of a straight-run diesel fraction and the "synthetic crude oil" derived from oil shale.