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

Abstract

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), Brunauer–Emmett–Teller isotherms (BET), X-ray photoelectron spectroscopy (XPS), hydrogen temperature-programmed reduction (H₂-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 Brønsted acidic sites were critical to increasing the DMM yield. The activity of V₂O₅/TiO₂ composite catalysts decreased with increasing Brønsted acidity, but the yield of DMM increased with an increasing amount of Brønsted 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 Brønsted acid sites.