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

The selective catalytic reduction of NOx by H-2 (H-2-SCR) was studied over Pt/MgO, Pt/gamma-Al2O3, Pt/ZrO2, and Pt/HZSM-5 catalysts. The H-2-SCR activities and N-2 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 H-2-SCR activity and N-2 selectivity. The inferior activities of Pt/MgO and Pt/gamma-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 N-2 or N2O, depending on the relative amounts of active hydrogen and nitrous species involved in the reduction. (C) 2015, Dalian Institute of Chemical Physics, Chinese Academy of Sciences. Published by Elsevier B.V. All rights reserved.