Titanosilsesquioxane Anchored on Mesoporous Silicas: A Novel Approach for the Preparation of Heterogeneous Catalysts for Selective Oxidations

Ti-polyhedral oligomeric silsesquioxanes (Ti-POSS) based heterogeneous catalysts were prepared by anchoring of a functional titanium-containing silsesquioxane on the surface of an ordered mesoporous silica (SBA-15) and a non-ordered silica (SiO2-Dav). The anchoring process was followed by IR spectroscopy, which leads to the condensation reactions between surface silanols of silicas and ethoxy groups. The heterogeneous character of catalysts checked by removing the solid catalyst by centrifugation and testing the residual liquid mixture show no significant loss of active species. Anchored heterogeneous catalysts show lower conversions with respect to reference materials prepared by direct grafting of titanocene on the same silica supports. It is also seen that the anchored materials display slightly better results than those obtained over reference titanium-silica catalysts with comparable metal loading.