Tailoring tunnel-type potassium-free manganese oxide catalyst via cerium substitution for catalytic NO reduction with NH3 at ultra-low temperatures

Abstract

Manganese oxide (KMn8O16, K-MO) was widely used for selective catalytic reduction (SCR) denitration due to its superior ability for activating and converting NO to N2 with NH3. However, the harmful K+ in its tunnel structure tends to consume NH3, leading to limited low-temperature activity and stability. Herein, a Ce substitution strategy was developed for the preparation of K-free Ce-MO for NH3-SCR. As-prepared Ce-MO exhibits a high NOx conversion (95%) at an ultra-low temperature of 75°C, with negligible activity decay within 60 h. Systematic characterizations elucidate the important role of Ce substitution in improvement of catalytic efficiency and stability for NO removal. The introduction of Ce not only eliminates harmful K+ and improves the stability of the catalyst, but also enhances the removal efficiency of NOx by the generation of oxygen vacancies. In addition, the formation of intermediate NH4NO3 is critical to improving the catalytic efficiency and stability over Ce-MO base on in-situ DRIFTS. This work provides a favorable strategy for the preparation of free-K tunnel-type manganese oxide catalyst for denitration with high activity and superior stability at ultra-low temperature.