Epoxidation of olefins on catalysts with highly isolated transition metal ions

The framework transition metal ions in microporous and mesoporous materials such as Ti-Silicalite-1 (TS-1), Fe-ZSM-5 and V-MCM-41 have been identified based on the UV resonance Raman spectroscopy. It is pointed out that the c onventionally used IR (Raman) band at 960 cm(-1) is not directly associated with the framework titanium ions in TS-1, while a resonance Raman band at 1125 cm(-1) is found to be essentially due to the asymmetric vibration of f ramework Ti-O-Si. To mimic the highly isolated transition metal ions in the framework of zeolites, Ti/SiO2, Fe/SiO2 and V/SiO2 catalysts were prepared using ion beam implantation and Ti/SiO2 and Si/Ti/SiO2 catalysts were prep ared by chemical grafting. These catalysts show pretty high activity and se lectivity for the epoxidation of styrene and cyclohexene using H2O2 as the oxidant. This work further confirms that the highly isolated transition met al ions are selective and active for the selective oxidation using H2O2 (RO OH) as the oxidant and the catalysts with highly isolated transition metal ions can be prepared with alternative methods instead of zeolitic synthesis .