Influence of support properties on H2 selective catalytic reduction activities and N2 selectivities of Pt catalysts

Abstract

The selective catalytic reduction of NOx by H2 (H2-SCR) was studied over Pt/MgO, Pt/γ-Al2O3, Pt/ZrO2, and Pt/HZSM-5 catalysts. The H2-SCR activities and N2 selectivities of the catalysts were strongly influenced by the amounts of Pt metal in the catalysts and the NOx adsorption capacities of the supports. The acidic surface of HZSM-5 increased the amount of metallic Pt on the support, decreasing the NOx adsorption capacity, resulting in much higher H2-SCR activity and N2 selectivity. The inferior activities of Pt/MgO and Pt/γ-Al2O3 are ascribed to the low amounts of metallic Pt and large NOx adsorption capacities of the supports as a result of their basic surfaces. Based on these results and in situ Fourier transform infrared spectroscopic studies of the reaction, it is proposed that the reduction products of nitrite/nitrate species at the Pt/support interface are N2 or N2O, depending on the relative amounts of active hydrogen and nitrous species involved in the reduction.