Selective CO methanation (CO-SMET) as a strategy for complete CO removal in fuel processing applications was investigated over Ru-based catalysts. The CO-SMET, in fact, seems to be a good alternative to the CO preferential oxidation (CO-PROX) for the applications on polymer electrolyte membrane fuel cells (PEM FCs) to transportation vehicles, boats, yachts and residential co-generators, as a CO-SMET reactor is inherently easier to control than the CO-PROX one. The present paper deals with the study on complete removal of CO in H-2-rich gas stream through CO-SMET over Ru-based catalysts supported on gamma Al2O3 carrier. All the catalysts, loaded with 3%, 4% and 5% Ru, respectively, were prepared by a conventional impregnation method and their CO removal performance was determined at the powder level in a fixed bed reactor. Starting from a synthetic reformate mixture of 0.5% CO, 40% H-2, 18% CO2, 15% H2O in He, the obtained results showed that CO complete conversion (residual outlet concentration lower than 2 ppmv, the analytical detection limit) was reached in a suitable temperature range where simultaneously both the CO2 methanation was kept at a low level and the reverse water gas shift reaction was negligible. The best results were obtained with 4% Ru-gamma Al2O3 in the range of 300-340 degrees C. (C) 2009 Elsevier Ltd. All rights reserved.