Thermal Restructuring of Silica‐Grafted TiClx Species and Consequences for Epoxidation Catalysis

TiCl₄ grafted to dehydrated silica is an industrially applied catalyst for the epoxidation of propylene. As with many heterogeneous catalysts, the precise nature of the surface species is not yet fully known, prohibiting reliable structure–activity correlations. In this study, the speciation and restructuring of site‐isolated Ti^IV Lewis acid centers was carefully investigated by using a variety of techniques. The initially formed ?SiOTiCl₃ species were found to restructure upon heating through the transfer of Cl ligands to the silica surface, eventually leading to tripodal (?SiO)₃TiCl species. The superior activity and stability of such tripodal species is demonstrated for catalytic olefin epoxidation under continuous flow conditions.