III International Conference

PP-III-43In this way, the content of BT and DBT was reduced from 1000 ppm S to 40 and 10 ppm,respectively. The possibility of the catalyst recycling was proved in oxidation of DBT.Study of BT and CHP conversion and sulphone yield depending on reagentsconcentrations, measurements in time of sulphone formation and CHP consumption,comparison of the products of CHP transformation during BT or DBT oxidation with theproducts of CHP decomposition in the absence of substrate, allowed us to draw conclusionsabout mechanism of the processes occurring with the assistance of MoO 3 /SiO 2 catalyst. In theabsence of substrate, CHP decomposes to phenol and acetone on acidic centers, and toacetophenone and 2-phenyl-2-propanol via radical route participated by molybdenum ions.Benzothiophenes oxidation is supposed to proceed via formation of intermediate complex ofmolybdenum oxide with CHP and substrate molecule (Scheme), that prevents CHPdecomposition. Conversion of the intermediate complex proceeds in two routs I and II to formoxide of BT or DBT, which than rapidly oxidizes to sulphone. The route I is electrophilicoxygen transfer to sulphur resulting in CHP conversion to 2-phenyl-2-propanol. The route IIrepresents radical conversion of benzothiophene and CHP to form 2-phenyl-2-propanol andacetophenone. The rout I predominates in the case of dibenzothiophene, whereas contributionof radical way II is remarkable during oxidation of the less reactive benzothiophene.Ph - C - OOH + S + [Mo 6+ O 3]HO 3Mo 6+IIδ−Sδ+IO S + Ph - C - OH + [Mo 6+ O 3]O - C - PhO[O] (rapid). .SOH + Ph - C - O + [Mo 6+ O 3]SOOSOH . + [Mo 6+ O 3] S + [Mo 5+ O 3H]O[Mo 5+ O 3H] + Ph - C -OOH [Mo 6+ O 3] + Ph - C - O.+ H 2O.Ph - C - O +[Mo 5+ O 3H] Ph - C - OH + [Mo 6+ O 3]Ph - C - O.Ph - CO(CH 3) + H 3C.Scheme. Proposed mechanism of benzothiophene and dibenzothiophene oxidation551