Effect of molybdenum valence in low Mo/Sn ratio catalysts for the oxidation of methanol to dimethoxymethane

A series of Mo/Sn (1:20, molar ratio) catalysts were prepared by two-step hydrothermal synthesis method, and the effect of calcination temperature of tin precursors on the reaction performance of methanol oxidation to dimethoxymethane (DMM) was investigated. The crystal structure, surface properties, redox property and valence change of molybdenum species of the catalyst were characterized by XRD, Raman, FT-IR, XPS, NH₃-TPD and H₂-TPR. The results showed that Mo1Sn20-600℃Sn catalyst exhibited better performance than other catalysts, achieving DMM selectivity of 90% with methanol conversion of 30% at 140 ℃. From the characterization results, the surface properties of the tin precursors affected the structure of catalyst, the degree of molybdenum oxide dispersion and valence of molybdenum species, and further influenced the performance of the catalysts. The high temperature calcination of tin precursors is more favorable for the generation of Mo⁶⁺ in the Mo1Sn20 catalyst.