Non-hydrolytic SiO2–TiO2 mesoporous xerogels—Efficient catalysts for the mild oxidation of sulfur organic compounds with hydrogen peroxide

SiO2–TiO2 mixed oxides with molar ratios Ti/(Si + Ti) ranging from 0.03 to 0.09 were prepared by a non-hydrolytic sol–gel process using SiCl4 and TiCl4 precursors. The texture and the distribution of Ti atoms in the resulting xerogels strongly depended on the Ti concentration as precursor and the reaction temperature. Mesoporous xerogels with very high surface area (up to 1200 m2 g−1) and pore diameters (up to 7.9 nm) can be obtained at 150 °C with a Ti loading of 6 mol%. These mesoporous materials showed excellent catalytic performances in the sulfoxidation reaction of different bulky sulfides (methyl phenyl sulfide, diphenyl sulfide), and thiophenes (benzothiophene, dibenzothiophene, tetrahydrothiophene, 4,6-dimethyl dibenzothiophene) with H2O2. In all the cases a very high selectivity toward H2O2 consumption as oxidizing agent was observed (>98%).