Grafting or tethering titanium alkoxo complexes on MCM-41? Strategies to prepare epoxidation catalysts

This paper describes the synthesis of titanium supported catalyst onto MCM-41 via chemical bonding. This has been done by first modifying the support in one step with a mixture of silanes-the synthesised triazine propyl triethoxysilane as a functional linker and methyltrimethoxysilane or hexamethyldisilizane as a capped agent to increase the hydrophobicity of the support and to mask the remaining silanol groups. Finally, titanium tetraisopropoxide has been immobilized by the reaction with the modified MCM-41. The materials without functional linker have also been prepared by reaction in one step of the capped agent and the titanium alkoxide precursor with the mesoporous silica. All the materials have been characterized by elemental analysis, X-ray diffraction, nitrogen adsorption techniques, FT-IR, ICP-MS, DRUV-Vis, Si-29 and C-13 MAS NMR, and TGA. The materials have been tested as cyclohexene epoxidation catalyst using tertbutylhydroperoxide as oxidant. (C) 2008 Elsevier Inc. All rights reserved.