Crystallization of hydrophobic mesoporous titano-silicates useful as epoxidation catalysts

Hydrophobic mesoporous titano-silicates (HyMTS) have been prepared at ambie nt temperature by a sol-gel technique using hexadecyl-trimethyl-ammonium ch loride in acid medium as templating surfactant. The gellation time increase s for low reaction temperatures and low H+/Si ratios. The amorphous materia ls thus obtained at long gellation times show hydrophobic properties and a lower number of OH bearing Si atoms as determined from Si-29 MAS NMR. In th e epoxidation of norbornene with H2O2 or Of cyclohexene with tert-butyl hyd roperoxide, HyMTS reaches selectivities for the epoxide of 95% or higher. T he epoxidation of cyclohexene by H2O2 also gives better selectivities to th e epoxide on these hydrophobic samples, compared to hydrophilic solids. It is suggested that hydrophobicity results from the slow kinetics of gellatio n. (C) 2000 Elsevier Science B.V. All rights reserved.