Efficient V2O5/TiO2 composite catalysts for dimethoxymethane synthesis from methanol selective oxidation

A series of V2O5/TiO2 composite catalysts (V2O5-TiO2-Al2O3, V2O5-TiO2-SiO2, V2O5-TiO2-Ce2O3 and V2O5-TiO2-ZrO2) were prepared by an improved rapid sol-gel method and the catalytic behavior for dimethoxymethane (DMM) synthesized from methanol selective oxidation was investigated. The physicochemical properties of catalysts were characterized by X-ray diffraction (XRD), BrunauerEmmett-Teller isotherms (BET), X-ray photoelectron spectroscopy (XPS), hydrogen temperature-programmed reduction (H-2-TPR), NH3 temperature programmed desorption (NH3-TPD), infrared spectroscopy of adsorbed pyridine (Py-IR) and transmission electron microscopy (TEM) techniques. The best catalytic performance was obtained on a V2O5-TiO2-SiO2 catalyst with methanol conversion of 51% and DMM selectivity of 99% at 413 K. Furthermore, the V2O5-TiO2-SiO2 catalyst displayed an excellent catalytic stability within 240 h. Results showed that more Bronsted acidic sites were critical to increasing the DMM yield. The activity of V2O5/TiO2 composite catalysts decreased with increasing Bronsted acidity, but the yield of DMM increased with an increasing amount of Bronsted acidic sites. The excellent performance of the V2O5-TiO2-SiO2 catalyst might come from its optimal acidity and redox properties, higher active surface oxygen species, together with more Bronsted acid sites.