Competitive Coordination-Induced Formation of Fe-O-Ce Structure in Beta Zeolite to Enhance Moderate-to-High Temperature Selective Catalytic Reduction of NO<sub>x</sub> with NH<sub>3</sub>
Xin Guo, Yuanjiang Wang, Minghao Hu, Na Young Kang, Baocang Liu, Xuan Xu, Jun Zhang
Abstract
Fe-based catalysts are capable of selective catalytic ammonia reduction (NH 3 -SCR) for NO x, while efficient loading of active components and optimization of reactive adsorption models are still required to achieve enhanced catalytic performance. Here, Ce and Fe dual-ion doped Ce-Fe-Beta zeolite catalysts were constructed via a facile ion exchange strategy for efficient NH 3 -SCR. The competitively coordinated interaction between Ce and Fe within Ce-Fe-Beta zeolite induces the transformation of aggregated Fe 2 O 3 species to incorporated Fe species with Fe-O and Fe-O-Ce bonds. The formed Fe-O-Ce structure enhances the adsorption of NO and reduces the energy barrier of the rate-limiting step (NO + O 2 → NO 2 ). The synergy between Ce and Fe can tune the electronic states of Fe species and makes the NH 3 -SCR reaction follow Langmuir–Hinshelwood and Eley–Rideal pathways. Thus, a high NO x conversion of ≥98% is achieved over Ce-Fe-Beta zeolite at 350–580 °C under a space velocity of 200 000 h –1 .