Carbon nanotube supported Pt-Ni catalysts for preferential oxidation of CO in hydrogen-rich gases

A series of carbon nano-tubes supported platinum-nickel catalysts were prepared and used for CO preferential oxidation in H2-rich streams. The catalysts were characterized by using N2-adsorption, XRD, HRTEM, H2-TPD and H2-TPR techniques. Effects of platinum and nickel loading amount, CO2 and H2O in the feed stream on the activity and selectivity over the catalysts were investigated. The results of catalytic performance tests show that the carbon nano-tubes supported Pt-Ni catalysts are very active and highly selective at low temperature for CO preferential oxidation in 1 vol. % CO, 1 vol. %O2, 50 vol. % H2 and N2 gases. Adding 12.5 vol. % of CO2 into the feed gases has slight negative influence on CO conversion. Adding 15 vol. % of H2O leads to a little decrease of CO conversion at the temperature range of 100-120 °C, which is proposed to be caused by capillary wetting of water in the micro-pores of carbon nano-tubes. As the reaction temperature is higher, adding water can improve CO conversion. The characterization results indicate that platinum species are in nano-particles uniformly dispersed on the carbon nano-tubes surface. There are two kinds of nickel species, one is interacted with platinum and likely to form Pt-Ni alloy in reduction process, the other is much highly dispersed on carbon nano-tubes and strongly interacted with the supports. The high activity of the catalysts is attributed to the interaction between Pt and Ni with the formation of Pt-Ni alloy.