Heterogeneous catalysis for thioanisole oxidation using hydrogen peroxide and Copper, Nickel and Zinc tungstates prepared by the polymeric precursor method

The oxidation of sulfides to sulfoxides and sulfones provides valuable sulfur-containing chemical compounds that are used in the pharmaceutical agrochemical industry. Although some tungsten catalytic systems have been applied to sulfide oxidation, the most desirable heterogeneous catalytic protocols have not been described. The copper, nickel and zinc tungstates powders obtained by the polymeric precursor method and the evaluation of their catalytic activity in thioanisole oxidation were investigated. Thioanisole was oxidized by hydrogen peroxide to sulfoxides and sulfones and the presence of catalyst accelerates the conversion. Of the three catalysts, copper tungstate was the most efficient in the conversion process followed by nickel tungstate and finally zinc tungstate. The copper tungstate has higher hydrogen consumption, indicating a higher oxygen content on the surface and the ability to increase surface mobility, which increases the conversion and selectivity of the process. The addition of 0.1 mL of hydrogen peroxide enhanced the conversion and increased the amount of sulfone produced. The ideal reaction time was 12 hours and the optimum temperature was 75 °C.