Elucidate the promotional effects of Sn on Ce-Ti catalysts for NH3-SCR activity

Abstract

Through a facile hydrothermal method, a series of mesoporous Ce0.3-x-Snx-Ti catalysts with high surface area have been prepared. A lot of characterizations were used to elucidate the promotional effects of SnO2 on Ce0.3-Ti catalysts for NH3-SCR activity. Compared with CeO2–TiO2 catalysts, the activity and SO2 resistance of the Ce0.2-Sn0.1-Ti catalyst were remarkably improved after doping Sn, and presented an excellent catalytic activity (above 90%) within 220–360 °C. The results suggested that Sn-doped Ce–Ti catalysts effectively increased lattice oxygen mobility, total acid amount accompanied with more Ce3+ and surface adsorbed oxygen species by insertion of doping ions. Furthermore, the reducibility of Ce0.2-Sn0.1-Ti sample was greatly improved by the reaction of 2Ce4+ + Sn2+ ↔ 2Ce3+ + Sn4+, and with the assistance of Ce2O3 to prevent the (NH4)2SO4, NH4HSO4 species and bulk-like sulfates from forming on the surface, leading to the better SO2 resistance. In addition, the in situ DRIFTS also illustrated that the NH3-SCR process occurred over Ce0.2-Sn0.1-Ti obeyed the Elye-Rideal mechanism.