Studies On Immobilization Of Salen-Mn Complexes Over The Supports And Catalytic Properties For The Epoxidation Of E-stilbene

Salen-Mn complex has been successfully grafted or encapsulated into mesoporous silicas HMS by chemically bonding or "ship in bottle" methods. FT-IR ,XRD and TG-DSC were adopted to characterize these catalysts. The epoxidation of E-stilbene was employed to check the catalytic performances of these catalysts. The results were as follows:(1) Three hexagonal mesoporous silicas (HMS) with different surface's groups (-OH, -NH₂, -CHO) have been successfully prepared by chemically grafting methods and were used to encapsulate Salen-Mn complexes by microwave irradiation, ultrasonic wave and conventional adsorption methods. The interaction between Salen-Mn complexes and the surface's groups of HMS were investigated by FT-IR and TG-DSC characterization technology. The dispersion degree of Salen-Mn complexes in the HMS was characterized by XRD. Mn loading was determined by coordinated titration. The effects of the surface's groups of HMS on the catalytic activity and selectivity of Salen-Mn complex for E-stilbene epoxidation were investigated. The results indicated that the HMS with surface's -NH₂ or -CHO could immobilize salen-Mn complex more efficiently than that with surface's -OH, therefore, the former possessed obvious higher salen-Mn loading and E-stilbene conversion and with a concomitant lower Mn leaching than the latter in the catalytic reaction process. Furthermore, the grafting some bulk large molecules on the outlet of HMS absorbed salen-Mn complexes could further reduce the Mn leaching and enhance the selectivity for the epoxides. Moreover, we found that microwave irradiation was the best method for preparing the salen Mn encapsulated HMS catalysts among the three methods.(2) Salen-Mn complexes have been successfully grafted onto mesoporous silicas HMS , HMS-PAMAM(G₀), HMS-PAMAM(G₁) and HMS-PAMAM(G₂) with the surface's -NH₂ groups by chemically...