Oxidation of diesel fuel sulfi des in the presence of molybdenum(VI) oxide was studied. DOI: 10.1134/S1070427210110170 At present, particular attention is being given to hydrometallurgical applications of a concentrate of sulfoxides, whose selectivity in recovery of noble metals compares well with that of individual sulfi des. In extraction capacity for numerous metals, this concentrate surpasses all the presently used industrial extractive agents [1]. The possibility of wide use of petroleum sulfoxides and sulfones, main products of oxidation of oil sulfi des, is due to the ability of the S=O functional group to form coordination compounds with water molecules, oxides, metal salts, organic and mineral acids, and phenols [2]. An effective and technologically convenient method for synthesis of sulfoxides is oxidation of oil sulfi des under interphase catalysis conditions. As oxidizing agents for sulfoxides commonly serve hydrogen peroxide, hydroperoxides [3, 4], and atmospheric oxygen [5]. A catalytic activity ion in this reaction is exhibited by compounds of molybdenum and tungsten [6]. There is published evidence about the composition of products and process conditions, but the reaction mechanism needs an additional study. Our study is concerned with fundamental kinetic aspects of the autocatalytic effect of molybdenum(VI) oxide on the reaction of peroxide oxidation of diesel fuel sulfi des. Sulfi des of the diesel fuel fraction are represented by derivatives of thiocyclopentanes, thiocyclohexanes, and dialkyl and phenylalkyl sulfi des [3].