Hydrogen Selective Catalytic Reduction of Nitrogen Oxide on Pt- and Pd-Based Catalysts for Lean-Burn Automobile Applications

The utilization of H₂ to catalytically treat NO emissions under lean-burn engine exhaust conditions was studied on Pt- and Pd-containing catalysts supported on CeO₂ and MgO. The catalytic performance was examined using a fixed-bed reactor whose dry effluent gas stream was analyzed by an online FTIR analyzer. The catalysts NO conversion and N₂ selectivity were measured in the range of 125-300⁰C with a feed gas composition of 0.05%NO/1%H₂/10%O₂/N₂. The CeO₂-based catalysts exhibited higher NO conversion, and the most effective catalyst was Pd/CeO₂, with a conversion of 67% and selectivity of 70% near 230⁰C. The prepared solids were characterized using different techniques (BET, ICP-OES, CO pulse chemisorption, STEM, EELS and EDS) to correlate the structural and morphological properties of the metallic phase and the support with the catalytic activity. CeO₂ is a more effective support as it yields higher metal dispersion and better facilitates the reduction of the Pt and Pd catalysts.