Mesoporous SBA-15 materials modified with oxodiperoxo tungsten complexes as efficient catalysts for the epoxidation of olefins with hydrogen peroxide

Abstract

A hybrid mesoporous SBA-15 material ( 2a) containing an oxodiperoxo tungsten complex of the type [WO(O 2) 2L] (L = pyrazolylpyridine) was synthesized by a post-grafting route. The organic–inorganic hybrid catalyst was characterized by means of XRD, N 2 adsorption–desorption and FT-IR. The catalytic property of 2a in the epoxidation of cyclooctene with H 2O 2 as the oxidant was investigated in comparison with other three kinds of hybrid tungsten containing SBA-15 materials bearing ethylenediamine, imidazole or 4,4′-bipyridine ligands. It was found that all oxodiperoxo tungsten catalysts were active at the reaction temperature of 55 °C with CH 3CN as solvent. However, only the catalyst with the pyrazolylpyridine ligand showed good recoverability and relatively high stability against leaching of active tungsten species. Moreover, this catalyst showed very high efficiency for H 2O 2 utilization, and its catalytic activity could be further improved by using solvent mixtures of CH 3CN and CH 3COOH.