Catalytic oxidation of benzyl alcohol over manganese oxide supported on MCM-41 zeolite

• Different precursors of manganese generate different species of MnOx.
• Low treated temperature generate high valence of Mnδ+ oxo.
• The high valence and reducibility of Mnδ+ oxo result in a high catalytic activity.

Potassium permanganate, nitrate and acetate acid precursors of manganese were used to as precursors of manganese to prepare dispersed manganese oxides on MCM-41 catalysts (MnOx/MCM-41), in order to compare the structure and activity. MnOx/MCM-41 were synthesized by impregnation method and calcined at different temperatures. The catalytic properties of these materials were investigated for the oxidation of benzyl alcohol using hydrogen peroxide as oxygen source. Catalysts were characterized by X-ray diffraction, N2 adsorption, H2 temperature programmed reduction, X-ray photoelectron spectroscopy and UV–Vis diffuse reflectance spectra. It was observed that the varieties of manganese precursors and calcination temperature affect the oxidation state and reducibility of MnOx, which play significant role in the catalytic process. The catalysts prepared from the potassium permanganate and acetate precursors exhibited the outstanding catalytic activity, which could be related to the reducibility of the surface Mnδ+ oxo species. It was found that the Mn4+ and Mn3+ oxo species present a higher intrinsic activity than that of Mn2+ oxo species.