Preparation and characterization of mesoporous VO x–TiO 2 complex oxides for the selective oxidation of methanol to dimethoxymethane

Abstract

Mesoporous VO x –TiO 2 with high surface areas were prepared using the procedure of evaporation-induced self-assembly combined with ammonia posttreatment. The samples were characterized by X-ray diffraction (XRD), laser Raman spectroscopy (LRS), transmission electron microscopy (TEM), N 2 adsorption, temperature-programmed reduction (H 2-TPR), microcalorimetry for the adsorption of NH 3, and isopropanol probe reaction. Their catalytic activities were evaluated for the reaction of selective oxidation of methanol to dimethoxymethane (DMM). It was found that the VO x –TiO 2 materials exhibited high surface areas with pore diameters of 4 nm. The vanadia species were highly dispersed in the VO x –TiO 2 within 30 wt% VO x content, evidenced by the results of XRD and LRS. The VO x –TiO 2 samples exhibited both surface acidic and redox properties. The surface acidity was further enhanced on the addition of SO 4 2 - . The catalyst SO 4 2 - / 30 VO x – TiO 2 exhibited good performance for the selective oxidation of methanol (57% conversion) to DMM (83% selectivity) at 423 K.