Abstract: A series of Mg-based mixed oxides MgM-n (M = Sn, Al, Ti, La, Ce, Zr; n = Mg/M atomic ratio) were prepared. The physicochemical properties of these mixed oxides were characterized by X-ray diffraction, N₂-adsorption/desorption, CO₂ temperature-programmed desorption, ultraviolet and visible diffuse reflectance spectroscopy, and electron spin resonance. The catalytic activity of MgM-n for the epoxidation of olefins was investigated with H₂O₂ as an oxidant. The results indicated that the catalytic performance and basicity of MgM-n mixed oxides were correlated to the type and doping amount of M species. The MgAl-4 and MgSn-4 samples showed a conversion and epoxide selectivity as high as 95% along with over 80% H₂O₂ efficiency for the epoxidation of styrene. However, MgSn-4 possessed lower surface basicity and more stable performance during consecutive reuse in comparison with MgAl-4. Moreover, MgSn-4 could catalyze the epoxidation of olefins of different structure with excellent performance. With the characteristic studies, it was presumed that such a superior performance of MgSn-4 could essentially be ascribed to the highly dispersed Sn⁴⁺ species and its unique structure as well as the proper basicity.

Key words: magnesium, tin, mixed oxide, hydrogen peroxide, olefin, epoxidation