High calcium resistance of CeO2–WO3 SCR catalysts: Structure investigation and deactivation analysis

Abstract

The SCR performances of CaO poisoning CeO2–WO3 and V2O5–WO3/TiO2 catalysts were prepared and compared for selective catalytic reduction of NO with NH3 (NH3–SCR). It was found that the CeO2–WO3 catalyst showed better calcium resistance than V2O5–WO3/TiO2 catalyst even when the CaO mass percentage reached up to 5wt%. In order to further understand the resistance mechanism, XRD, Raman, XPS, H2-TPR, NH3-TPD and in situ DRIFTS were used to analyze and explore the changes of CeO2–WO3 catalysts before and after the CaO deactivation. The results manifested that the introduction of Ca species not only affected CeO2 lattice but also led to CaWO4 formation on the surface. Additionally, although CaO increased the surface chemisorbed oxygen and Ce4+ species, the reducibility and Lewis acid sites, NH3 chemisorbed amount and Brønsted acid sites were greatly inhibited after deactivation. Furthermore, the enhanced NO2 adsorption capacity after the alkaline Ca species introduction could partially offset the negative effect in the loss of acid sites over the catalyst surface, which might be the primary reason for stronger CaO resistance of CW catalyst than traditional V2O5–WO3/TiO2 catalyst.