Nanosponge TS-1: A Fully Crystalline Hierarchical Epoxidation Catalyst

Abstract

Epoxide production by organic synthesis raises environmental and safety issues, especially for industrially relevant substrates larger than C-4, which lack effective catalysts for direct epoxidation. However, titanosilicates activate hydrogen peroxide for the epoxidation of C(sic)C double bonds. For such purposes, active site accessibility must nevertheless be tuned for each substrate. Accordingly, this paper reports on the preparation, characterization and catalytic properties of an MFI titanosilicate nanosponge (nsTS-1). nsTS-1 is prepared by post-synthesis titanium impregnation of a pure silica MFI nanosponge, producing a fully crystalline and highly open catalyst with a total pore volume of 0.77 cm(3)g(-1). Due to the high external surface of the nanolayered domains, Ti forms isolated framework-attached Ti sites rather than extra-framework TiO2. As a result, the structure of nsTS-1 is more defined and uniform than the structure of other layered titanosilicate catalysts (e.g., silica-titania pillared TS-1). Catalytic tests show: i) that nsTS-1 efficiently catalyzes the epoxidation of cyclic olefins and terpenes and ii) cyclooctene and linalool conversion linearly increases with the external surface area and mesopore volume of the catalyst. Overall, the presented findings enable to tailor effective catalysts for direct epoxidation, thereby potentially reducing costs and waste in the production of large epoxides.