Crystallization of hydrophobic mesoporous titano-silicates useful as epoxidation catalysts

Abstract

Hydrophobic mesoporous titano-silicates (HyMTS) have been prepared at ambient temperature by a sol–gel technique using hexadecyl-trimethyl-ammonium chloride in acid medium as templating surfactant. The gellation time increases for low reaction temperatures and low H +/Si ratios. The amorphous materials thus obtained at long gellation times show hydrophobic properties and a lower number of OH bearing Si atoms as determined from 29Si MAS NMR. In the epoxidation of norbornene with H 2O 2 or of cyclohexene with tert-butyl hydroperoxide, HyMTS reaches selectivities for the epoxide of 95% or higher. The epoxidation of cyclohexene by H 2O 2 also gives better selectivities to the epoxide on these hydrophobic samples, compared to hydrophilic solids. It is suggested that hydrophobicity results from the slow kinetics of gellation.