Synthesis and Characterization of Silica-supported μ-Dichloro Bridged Dimolybdenum(V) Complex and its Catalysis Activity in Epoxidation of Cyclohexene

Silica-supported μ-dichloro bridged di-molybdenum(V)complex catalyst, namely (MoOCl)2/SiO2, was synthesized and then characterized by the infrared spectra, UV-vis spectra, magnetic analysis, etc. The Mo(V)complex grafted in silica was used as catalyst in the epoxidation process of cyclohexene, and its catalytic activity and selectivity were studied. The experimental results show that after treating with the epoxidation agent t-BuOOH previously, the complex catalyst prepared possesses excellent activity and selectivity for the epoxidation of cyclohexene, and it is also found that in the complex catalyst, the active catalytic component is Mo(VI) and isn′t Mo(V). In the present of the catalyst, the reaction mechanism of cyclohexene with t-BuOOH was described. New methods were established to determine the amount of Mo in the catalyst and to analysis the cyclohexane oxide by using the gas chromatograph (GA). Under following conditions: when n (t-BuOOH)=0.1mol, n(C6H10) : n(t-BuOOH) = 3 : 1, volume of solvent about 5mL, reaction temperature 80℃, reaction time 60min and the weight of molybdenum in the catalyst~0.021g, the yield of cyclohexane oxide is more than 99% (with respect to the amount of t-BuOOH ) and its purity is about 99.5%. The catalyst used repeatedly for 5 times can still possess both a high catalytic activity and selectivity, and the yield of cyclohexane oxide can also still remain at about 99%.