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.