The stability of Co₃O₄, Fe₂O₃, Au/Co₃O₄ and Au/Fe₂O₃ catalysts in the catalytic combustion of lean methane mixtures in the presence of water

Nano-sized Co₃O₄, Fe₂O₃, Au/Co₃O₄ and Au/Fe₂O₃ catalysts were prepared and evaluated for catalytic combustion of lean methane-air mixtures. Characteristics and catalytic activities under dry and wet feed conditions were investigated at gas hourly space velocities up to 100 000 h^-1 mimicking the typical flow and conversion requirements of a catalytic system designed to treat a ventilation air methane stream. In order to gain a better understanding of the interaction between H₂O and the catalyst surface, temperature-programmed desorption of water over fresh and used samples were studied, and supported by other catalyst characterization techniques such as N₂-adsorption desorption, XRD, TEM, SEM and XPS analyses. The activity measurements of the catalysts studied identify Co₃O₄ as the most active material. Co-precipitating gold particles with cobalt oxide or iron oxide do not enhance the activity of the catalyst, which is most likely due to blocking the active site of support by the gold particle. The presence of strong hydroxyl bonds on the catalyst surface is substantiated by TPD and XPS analyses, and is suggested to be responsible for the rapid deactivation of Fe₂O₃ and Au/Fe₂O₃ catalysts.