Preparation of titanium molecular species supported on mesostructured silica by different grafting methods

Titanium supported on SBA-15 mesoporous silica has been synthesised containing different titanium loading prepared by chemical grafting using titanocene dichloride as precursor and over different treated silica surfaces. A comparative study using MCM-41 mesoporous silica as support is also reported. The type of silica support and its surface properties as well as the initial concentration of Ti precursor in the organic solution influences clearly the incorporation of Ti species. The materials after grafting treatment were characterised by different conventional techniques including XRD, Fr-IR, DR UV-Vis and nitrogen adsorption. The titanium containing SBA-15 silica shows hexagonal mesoscopic order and pore sizes up to 70 Angstrom with surface areas up to 600 m(2)/g and titanium content ranging from 1 to 3 wt.%. DR UV-Vis of Ti containing SBA- 15 silica after removal of the organic ligand shows the presence of Ti isolated species tetrahedrally coordinated and the absence of bulky TiO2 phases. Likewise, these materials upon calcination were catalytically active for the epoxidation of styrene with TBHP exhibiting a significant selectivity towards the epoxide with negligible leaching of Ti species. (C) 2002 Elsevier Science B.V. All rights reserved.