The partial oxidation of methanol to formaldehyde on titania-supported vanadium oxide was studied using temperature-programmed desorption (TPD) and thermal gravimetric analysis (TGA). Calorimetry was also used to measure the heats of reoxidation of partially reduced vanadia/titania catalysts. The TPD results showed that the activation energy for the oxidation of adsorbed methoxides to formaldehyde depends on the extent of reduction of the supported vanadia layer. On supported V2O5 and V2O3 formaldehyde was produced at 535 and 630 K, respectively. The TPD results also demonstrated that the thermal stability of the supported vanadia was coverage dependent and suggested that polyvanadate species are more thermally stable than isolated vanadyls. The heat of reoxidation of partially reduced supported vanadia layers was measured calorimetrically and found to be 240 L 10 kJ/mol of O-2.