Insight into the promotion effects of Ce on the performances of V − Ti based catalyst for low-temperature NH3 − SCR: In-situ spectroscopy studies

The addition of Ce to V − Ti based catalysts is a promising way to improve the middle and low temperature activity for selective catalytic reduction of NO with NH₃ (NH₃ − SCR). In this study, a series of V − Ce loaded TiO₂ catalysts were prepared by impregnation method and studied by in situ spectroscopy experiments and ex situ characterizations. Results show that the SCR reaction on the surface of V − Ce/TiO₂ catalysts obeys the Eley − Rideal mechanism. The presence of Ce in V − Ce/TiO₂ catalysts strengthens the NH₃ adsorption energy of V and promotes its rupture of N − H bond, thus facilitating the reactions, with 100 % NO conversion and 100 % N₂ selectivity obtained at 250 °C over 2 V-10Ce/Ti. During the reaction, the Ce⁴⁺ ions are reduced by NH₃ + NO to yield N₂ and Ce³⁺ ions (the reduction half cycle), which will then be re-oxidized to Ce⁴⁺ ions by O₂ (the oxidation half cycle), thereby ensuring the proceeding of the overall reaction.