Selective methanation of CO in a H,rich stream performed over different supported-nickel catalysts showed that Ni-CeO2 and Ni-Cr2O3 were the most effective catalysts for complete removal of CO through selective methanation to decrease a concentration of CO from 1.6 vol % to ppm level (<50 ppm) in a microchannel reactor, and among them a nickel catalyst promoted by Cr2O3 proved to be robust for over 180 h without any degradation in performance of selective CO methanation.