Surface reactivity of NiO/Co3O4 and Fe2O3/Co3O4 nanocomposite catalysts:: interaction with methanol

In this paper the reactivity of two nanocomposite supported oxides (NiO/Co3O4 and Fe2O3/Co3O4) toward methanol, was studied at atmospheric pressure and under high vacuum conditions. Methanol interacts dissociatively with the Fe2O3/Co3O4 surface whereas only a weak interaction was revealed on NiO/Co3O4. It is remarkable the formation, at RT, of formic acid on the surface of the NiO/Co3O4 supported oxide. Around 323 K the formation of carbon dioxide is evident. Formic acid is very slightly bonded to the surface and can be easily removed by a N-2 flow. In the Fe2O3/Co3O4 supported oxide is evident, besides formic acid, the formation at RT of formate species whose intensity increases with temperature. Methanol interacts molecularly and dissociatively with both the supported oxide under HV conditions. The desorption of molecularly chemisorbed methanol is accompanied by the decomposition and fragmentation of the alcohol; at higher temperature, in contrast, oxidation and recombination reactions compete with the methoxy groups desorption. The reactivity toward methanol of the pure and nanocomposite oxides was compared. (C) 2004 Elsevier B.V. All rights reserved.