Selective removal of CO by methanation of carbon oxides has been performed over wash-coated supported metal catalysts in a microchannel reactor with simulated reformate feeding. The primary screening over a series of Ru and Ni-based catalysts shows that methanation activity is markedly dependent on the type of metal, the metal loadings and the promoter. Ni/CaO/Al2O3 catalyst exhibits the highest methanation activity with CO conversion higher than 93% and a relatively low conversion Of CO2 into methane among investigated catalysts at 300 degrees C under the operating condition. The appropriate temperature for selective methanation was identified to be 250 degrees C below which CO methanation preferentially and exclusively occurs. The effect of reaction temperature and gas additives such as steam and gaseous oxygen on the methanation performance is presented in terms of catalytic activity, selectivity, and methane yield. The regulation of carbon oxides methanation on Ni/CaO/ Al2O3 catalyst by gaseous oxygen was realized by a switchover of the reaction pathway from combustion reaction in the presence of gas phase oxygen to the methanation upon the complete consumption of oxygen and the dynamic behaviour of catalyst surface induced by the interplay of the catalyst surface and the gas phase reactants. (c) 2007 Elsevier B.V. All rights reserved.