Preferential CO methanation in a reformate gas was investigated over 10 wt.% Ni/CeO2 pelleted catalyst in the fixed-bed reactor. It provided the reduction of the CO concentration in the reformate gas to less than 10 ppm over wide temperature interval (250-300 degrees C), while keeping hydrogen consumption relatively low. The design, scale-out, and operation of a preferential CO methanation reactor with integrated heat-exchanger were reported. The nickel-ceria catalyst was deposited onto metal gauzes, assembled into catalytic blocks. Direct contact of the catalyst with metal support provided high heat conductivity of the assembly and feasible temperature control upon variation of operation regimes. Nickel-ceria catalyst showed high activity and selectivity for the reaction of CO methanation in the presence of CO2 excess. The preferential CO methanation reactor allowed the decrease of CO concentration to less than 20 ppm in realistic reformate generated by fuel processor via the reaction of methane steam reforming followed by CO water gas shift reaction. (C) 2011 Elsevier B.V. All rights reserved.