Comparison of different prepared Mn-MCM-41 catalysts in the catalytic epoxidation of alkenes with 30% H2O2

Abstract

Manganese containing mesoporous materials Mn-MCM-41 were prepared by template-ion exchange (TIE), in situ reduction (ISR), direct hydrothermal (DHT) and wetness impregnation (WI) methods. The samples were characterized by XRD, N2 adsorption–desorption, HR-TEM, TG, UV–Vis, H2-TPR and ESR techniques, which illustrated that the definite structure of the MCM-41 was retained after introducing Mn into MCM-41 by different method. The catalytic activity and selectivity of the Mn-MCM-41 in the epoxidation of styrene with 30% H2O2 as an oxidant agent were explored. The TIE catalysts showed the highest activity but Mn2+ was leached during the reaction. The ISR catalysts exhibited high activity for epoxidation of styrene. Furthermore, recycling studies proved the ISR catalysts as heterogeneous catalysts, which did not lose the catalytic activity after four recycles appreciably. However, the DHT and WI catalysts showed poor performance in the catalytic epoxidation of styrene. Various parameters such as different reaction molar ratio of H2O2/styrene, catalyst amount, and kinds of solvents were studied to optimize the reaction conditions.