Rod-like CeO₂ Cluster-Supported MnO_<i>x</i>-WO₃ Catalysts for Selective Catalytic Reduction of NO_<i>x</i> with NH₃: Catalytic Performance and H₂O/SO₂ Influence

A rod-like CeO2 cluster synthesized by the urea hydrothermal method was used to prepare the supported MnyWz/CeO2 for NOx removal by NH3-SCR. Catalyst component-structure-performance relationship was discussed based on a selective catalytic reduction (SCR) activity test and catalyst characterizations. The influence of H2O and SO2 on SCR performance for catalysts with different components was compared and analyzed meticulously. The results indicated that WO3 loading broadened the catalyst temperature window by increasing surface acidity, and excellent low-temperature SCR activity was obtained for MnyWz/CeO2 catalysts with improved redox capacity by MnOx substitution. Due to the influence on NH3 adsorption and activation, the addition of H2O reduced NOx conversion of catalysts at low temperatures and decelerated the decline of SCR activity at high temperatures reversibly. Meanwhile, N2O formation was inhibited profitably. The introduction of SO2 led to the irreversible deactivation of the representative catalysts at different temperatures by changing their acidity and redox capacity simultaneously. Because the main limiting factors of SCR activity for sulfated catalysts were closely related to the reaction temperature, the existence of H2O was necessary to observe the real-time reactivity change during SO2 durability tests above 300 °C. Enhancing contact inhibition between CeO2 and SO2 was proven as an effective method to improve the SO2 resistance of cerium-based catalysts.