Silylation of titanium-containing amorphous silica catalyst: Effect on the alkenes epoxidation with H2O2

The surface of a Ti/SiO2 catalyst was silylated using hexamethyldisilazane (HMDS) and tetramethyldisilazane (TMDS) as silylating reagents in vapor phase. The silylation of silanol (Si-OH) on the catalysts was confirmed by diffuse reflectance UV-vis, DRIFT spectroscopy and solid-state Si-29 MAS NMR techniques. Titanium-containing mesoporous amorphous silica has been successfully modified by trimethylsilylation enhances its hydrophobicity producing an increase in the hydrogen peroxide efficiency and in selectivity to epoxide in the epoxidation of alkenes with H2O2. These effects are more evident when the hydrogen peroxide concentration is higher. As the results show the silylation degree reached is higher when TMDS is employed, showing the catalysts silylated with TMDS a better hydrogen peroxide efficiency and selectivity to epoxide. (C) 2010 Elsevier B.V. All rights reserved.