Active sites assembly effect on CeO2-WO3-TiO2 catalysts for selective catalytic reduction of NO with NH3

Each active site on catalysts with multiple active sites is vital important to their catalytic performance, how to assemble these active sites to obtain the best performance is an attractive spot. In this work, the CeO2-WO3-TiO2 (CeWTi: Ce-W/Ti, Ce/W/Ti and W/Ce/Ti) catalysts with different loading sequence of CeO2 (redox site) and WO3 (acidic site) were prepared to investigate the active sites assembly effect on their catalytic performance for NH3-SCR reaction. Catalytic activity evaluation proposed that active sites assembly effect depends largely on the ratio of CeO2/WO3 and had a significantly influence on NOx removal efficiency over CeWTi catalysts (espeicially for Ce0.3W0.1Ti0.8 (mass weight)). From the analysis of surface properties, different assemble of active sites would affect the redox and acid properties of CeWTi catalysts. Reaction process study by in situ DRIFT suggested that the reaction over CeWTi catalysts followed Langmuir-Hinshelwood (L-H) mechanism at low temperature but Eley-Rideal (E-R) mechanism at high temperature. Based on the analysis of the reaction process, it was concluded that the control step of NH3-SCR reaction over Ce0.3W0.3Ti0.8 catalysts was the adsorption and activation of NH3. Through this study, we constructed a study strategy of active sites assembly effect that might contribute to understand the catalytic mechanism over catalysts with multiple active sites.