A TPD study of the partial oxidation of methanol to formaldehyde on CeO2-supported vanadium oxide

The partial oxidation of methanol to formaldehyde on ceria-supported monolayer vanadium oxide was studied using temperature-programmed desorption (TPD), microcalorimetry, and X-ray photoelectron spectroscopy (XPS). Methanol TPD demonstrated that the activation energy for the dehydrogenation of adsorbed methoxides to produce formaldehyde is a function of the oxidation state of the vanadium cations in the supported layer. During CH3OH TPD, CH2O was produced at 525, 550, and 610 K, on V5+, V4+, and V3+, respectively. The heat of reoxidation of supported vanadia/ceria samples that had been reduced by performing a CH3OH TPD experiment was measured using microcalorimetry and found to be 245 kJ/mol of O2. The heat of adsorption of CH3OH on the vanadia layer was also measured and found to be 80 kJ/mol on both oxidized and partially reduced VOx/CeO2 samples. The implications of these results for understanding the mechanism of methanol oxidation on supported vanadia are discussed.