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

摘要

A series of carbon nano-tubes supported platinum-nickel catalysts were prepared and used for CO preferential oxidation in H_2-rich streams. The catalysts were characterized by using N_2-adsorption, XRD, HRTEM, H_2-TPD and H_2-TPR techniques. Effects of platinum and nickel loading amount, CO_2 and H_2O 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. %O_2,50 vol. % H_2 and N_2 gases. Adding 12.5 vol. % of CO_2 into the feed gases has slight negative influence on CO conversion. Adding 15 vol. % of H-2O leads to a little decrease of CO conversion at the temperature range of 100-120 ℃, 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.