Selective oxidation of methanol to form dimethoxymethane and methyl formate over a monolayer V2O5/TiO2 catalyst

The oxidation of methanol over highly dispersed vanadia supported on TiO2 (anatase) has been investigated using in situ Fourier transform infrared spectroscopy (FTIR), near ambient pressure X-ray photoelectron spectroscopy (NAP XPS), X-ray absorption near-edge structure (XANES), and a temperature-programmed reaction technique. The data were complemented by kinetic measurements collected in a flow reactor. It was found that dimethoxymethane competes with methyl formate at low temperatures, while the production of formaldehyde is greatly inhibited. Under the reaction conditions, the FTIR spectra show the presence of non-dissociatively adsorbed molecules of methanol, in addition to adsorbed methoxy, dioxymethylene, and formate species. According to the NAP XPS and XANES data, the reaction involves a reversible reduction of V5+ cations, indicating that the vanadia lattice oxygen participates in the oxidation of methanol via the classical Mars–van Krevelen mechanism. A detailed mechanism for the oxidation of methanol on vanadia catalysts is discussed.