Oxidation of 2-thiobenzyl-4,6-dimethyl-pyrimidine with hydrogen peroxide over Mo oxides, Mo suboxides and mixed Mo-Sb oxides catalysts

The oxidation of 2-thiobeniyl-4,6-dimethyl-pyrimidine was investigated over catalysts based on MoO3, Mo suboxides and mixed Mo-Sb oxides to obtain 2-thiobenzyl-4,6-dimethyl-pyrimidine sulfoxide. The chemoselectivity was found to vary with the oxidation state of the Mo atoms, the morphology of the Mo oxide crystals and the concentration of Sb in the structure. The best chemoselectivity (about 80%) resulted from Mo8O23. The H2O2 efficiency was also found to depend on these parameters. For Mo suboxides the best efficiency was obtained on Mo8O23, which suggested that the efficient catalysts are those possessing Mo in a reduced oxidation state. The presence of Sb changed the behavior of the catalysts and the higher H2O2 efficiency resulted for the catalysts containing Mo in its highest oxidation state. (C) 2002 Elsevier Science B.V. All rights reserved.