Direct synthesis of organically modified Ti-SBA-15 materials

Abstract

Organically-modified Ti-SBA-15 materials have been prepared through a direct synthesis procedure based on the co-condensation of tetraethyl orthosilicate (TEOS), alkyltriethoxysilanes (R-TES) and titanocene dichloride as silicon, organic species and titanium sources respectively. The prehydrolysis time for the TEOS and the amount and type of alkyl functionality were studied in order to achieve mesostructured organic-modified Ti-SBA-15 materials. The synthesized samples were assayed in the catalytic epoxidation of 1-octene with TBHP as oxidant. The catalytic results reveal a direct correlation between the activity of the catalyst per titanium site and the length of the alkyl chain. Higher lengths of the alkyl chain induce a significant increase of the activity of the titanium sites due to the enhancement of their hydrophobic microenvironment. Likewise, improved efficiency in the use of the oxidant has also been observed when using organic modified Ti-SBA-15 materials, being correlated this effect with the reduction of the non-oxidative decomposition of TBHP. Finally, the reutilisation tests indicate very high stability of the prepared catalysts in epoxidation reactions with TBHP.