Ti-Beta zeotypes with open Ti(OSi)3OH sites for the efficient epoxidation of cyclohexene with H2O2

Ti-Beta zeotypes, possessing three-dimensional 12-membered ring pore-opening channels, have shown some superior catalytic performance in the epoxidation of bulky cycloalkenes with hydrogen peroxide (H2O2) in comparison with other titanosilicate zeotypes. However, some further improvement on the catalytic activity and selectivity of Ti-Beta zeotypes is still demanded for the industrialization of cycloalkenes epoxidation. In the present work, the catalytic performance of Ti-Beta in cyclohexene epoxidation was significantly improved via the transformation of their closed Ti(OSi)(4) sites into the open Ti(OSi)(3)OH ones by a simple NH4F treatment. Based on the extensive characterization results, it is found that the NH4F-treated Ti-Beta zeotypes with open Ti(OSi)(3)OH sites, named OH-Ti-Beta, possess a stronger Lewis acidity that is favorable to the production of cyclohexene oxide (CHO) from the epoxidation of cyclohexene with H2O2, compared to the parent Ti-Beta with closed Ti(OSi)(4) sites. Moreover, OH-Ti-Beta catalysts are reusable after the calcination of the deactivated zeotypes. Hence, it is expected that the current developed NH4F treatment can obtain efficient OH-Ti-Beta catalysts industrially applied in cyclohexene epoxidation.