User-friendly synthesis of highly selective and recyclable mesoporous titanium-silicate catalysts for the clean production of substituted p-benzoquinones

Abstract

Mesoporous titanium-silicates have been prepared following the evaporation-induced self-assembly (EISA) methodology and characterized by elemental analysis, XRD, N₂ adsorption, SEM, DRS UV–Vis and Raman techniques. The use of acetylacetone during synthesis allowed the formation of highly dispersed dimeric and/or small oligomeric Ti species, within the mesostructured silica network, to be realized. The materials catalyse oxidation of alkylsubstituted phenols to corresponding p-benzoquinones with 100% selectivity using the green oxidant – 30% aqueous hydrogen peroxide. The titanium-silicates prepared by the convenient and versatile EISA-based procedure reveal the true heterogeneous nature of the catalysis and do not suffer from titanium leaching. They show advantages over other types of mesoporous Ti,Si-catalysts, such as TiO₂–SiO₂ mixed oxides and grafted Ti/SiO₂, in terms of the catalyst stability and reusability.