New aspects on a low-medium temperature mechanism of H2-assisted C3H6-SCR over xAg-CeZr catalyst

Abstract

The spherical xAg-CeZr catalysts were prepared by a continuous solvothermal-impregnation method and applied to H2-assisted C3H6-SCR. Adding H2 significantly promoted NO conversion between 150 and 500 °C. The outstanding NO conversion and N2 selectivity over 2%Ag-CeZr at 200 °C achieved 71.7% and 45.3%, and its C3H6 conversion rate was significantly improved. Multi-technology characterizations results showed that active Ag+, Ce3+ and Oα species were important factors for the excellent activity in H2-C3H6-SCR. The in situ FT-IR analysis indicated that NO adsorption capacity, the reactivity of adsorbed NO species (monodentate nitrate, bidentate nitrate and monodentate nitrite) and CxHyOz species (enolic species, formate, carboxylate), and the formation of crucial intermediates were remarkably improved on account of adding H2, further promoting the SCR catalytic performance. Different sequences of H2 admission did affect its promotion mechanism to the reaction system. We proposed a main pathway for H2-C3H6-SCR over Ag-CeZr: NO + C3H6 + H2 + O2 → NO2–/NO3– + CxHyOz → ONCs → –NCO + –CN → N2 + CO2 + H2O. The present work confirmed that H2 would enhance the C3H6-SCR performance through different pathways over spherical Ag-CeZr catalysts.