Insights into the co-doping effect of Fe3+ and Zr4+ on the anti-K performance of CeTiOx catalyst for NH3-SCR reaction

A novel K-resistant Fe3+ and Zr4+ co-doped CeTiOx catalyst was first prepared by co-precipitation method for the ammonia-selective catalytic reduction (NH3-SCR) of NOx. On the premise of retaining the outstanding catalytic activity of CeTiOx catalyst, Fe3+ and Zr4+ co-doping efficiently improves its K-resistance with superior NOx conversion up to 84% after K-poisoning. Specially, the grain growth during the second calcination after K poisoning is successfully inhibited by Fe3+ and Zr4+ co-doping. Consequently, the large specific surface area with increased acid sites and efficiently retained reducibility over K-poisoned FeZrCeTiOx catalyst are realized, which prompt NH3 activation and NO oxidation, further benefit NH3-SCR. Besides, NH3-SCR reaction over CeTiOx and FeZrCeTiOx catalysts follows a possible L-H mechanism, and K-poisoning makes no change to it. Finally, a reasonable anti-K poisoning mechanism of FeZrCeTiOx catalyst is proposed: the excellent K-resistance is attributed to part of Fe and Zr are sacrificed to form Fe-O-K and Zr-O-K species protecting the active site Ce-O-Ti from K-poisoning, as well as the additional reducibility and surface acidity brought from Fe-O species with Zr prompting its uniform distribution.