Comparative studies for CO oxidation and hydrogenation over supported Pt catalysts prepared by different synthesis methods

Abstract

Pt supported on TiO2 and ZrO2 catalysts were synthesized via wet impregnation and deposition precipitation methods. The catalysts were tested for CO removal from reformate gas following the water-gas shift reaction for on-board fuel processors. Tests included oxidation of CO to CO2, preferential oxidation of CO to CO2 in the presence of H2 (PROX), and hydrogenation of CO to CH4 (selective methanation, SMET). The Pt–ZrO2 catalysts showed better metal dispersions, particle sizes, lower degrees of reduction and higher oxygen storage capacities than the TiO2 supported catalysts. All catalysts showed low activity for the oxidation of CO in the PROX reaction, due to H2 and O2 spillover effects. ZrO2, with its high reducing properties and strong metal-support interactions, was found to be the best support for hydrogenation of CO. ZrO2 induced small well-dispersed Pt particles that were key parameters in this reaction. Both Pt–ZrO2 catalysts showed CO conversions over 99% above 350 °C with high CH4 selectivities (99%). The study shows advantageous effects of strong metal to support interactions, like participation of MOx (support) species in activating the CO molecule. The CO concentration was effectively reduced to the desired ppm levels (<10 ppm) required for optimum fuel cell operation.