Comparison of titanosilicates with different topologies as liquid-phase oxidation catalysts

Titanosilicates, with isolate and tetrahedrally coordinated Ti⁴⁺ ions in zeolite framework, have shown their great potentials in the liquid-phase selective oxidation reactions. The usage of H₂O₂ as the oxidant helped to build up environment-friendly chemical processes by giving H₂O as the sole co-product. Four titanosilicates of Ti-MCM-68, Ti-MOR, Ti-MWW and TS-1, with distinct crystalline topologies, were included in present study, whose catalytic performances were compared in the epoxidation of alkenes and the ammoximation of ketones. Ti-MCM-68, as a recently discovered titanosilicate, showed attractive advantages in the epoxidation reactions, while its catalytic performance in the ammoximation reactions was inferior to the other three titanosilicates. However, the cyclohexanone conversion and oxime selectivity could reach ∼99% over Ti-MCM-68 titanosilicate under optimized reaction conditions, indicating that it could also be taken as a promising catalyst for ammoximation reaction.