Insights into the co-doping effect of Fe and Zr on the anti-K performance of CeTiO catalyst for NH-SCR reaction.

A novel K-resistant Fe and Zr co-doped CeTiO catalyst was first prepared by co-precipitation method for the ammonia-selective catalytic reduction (NH-SCR) of NO. On the premise of retaining the outstanding catalytic activity of CeTiO catalyst, Fe and Zr co-doping efficiently improves its K-resistance with superior NO conversion up to 84% after K-poisoning. Specially, the grain growth during the second calcination after K poisoning is successfully inhibited by Fe and Zr co-doping. Consequently, the large specific surface area with increased acid sites and efficiently retained reducibility over K-poisoned FeZrCeTiO catalyst are realized, which prompt NH activation and NO oxidation, further benefit NH-SCR. Besides, NH-SCR reaction over CeTiO and FeZrCeTiO catalysts follows a possible L-H mechanism, and K-poisoning makes no change to it. Finally, a reasonable anti-K poisoning mechanism of FeZrCeTiO 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.