Tandem Reaction on Ru/Cu-CHA Catalysts for Ammonia Elimination with Enhanced Activity and Selectivity

• Published in: Environmental science & technology 2025-01
• Main Authors: An, Qi, Zhang, Mengyuan, Liu, Jianhua, Chen, Tingxu, He, Yueqing, Liu, Diru, Yu, Yunbo, Xu, Guangyan, He, Hong
• Format: Article
• Language: English
• ISSN: 0013-936X; 1520-5851; 1520-5851
• DOI: 10.1021/acs.est.4c10396

Ammonia emissions from vehicles and power plants cause severe environmental issues, including haze pollution and nitrogen deposition. Selective catalytic oxidation (SCO) is a promising technology for ammonia abatement, but current catalysts often struggle with insufficient activity and poor nitrogen selectivity, leading to the formation of secondary pollutants. In this study, we developed a bifunctional Ru/Cu-CHA zeolite catalyst for ammonia oxidation, incorporating both SCO sites (Ru) and selective catalytic reduction sites (SCR, Cu). Various characterizations, including HAADF-STEM, XAFS, and H -TPR, revealed that Cu cations are dispersed within the CHA zeolite, while RuO clusters and nanoparticles are present both inside and on the surface of the zeolite. DRIFTS-MS, Raman spectroscopy, and DFT calculations confirmed that NH adsorbed on Cu Lewis acid sites efficiently reduced RuO with a lower energy barrier, significantly enhancing the low-temperature activity of the Ru/Cu-CHA catalyst. Additionally, Cu cations further facilitated the elimination of byproducts (NO ) via the tandem SCR reaction, thus greatly improving the nitrogen selectivity. This synergistic effect contributed to high catalytic activity (>94% at 200 °C) and excellent nitrogen selectivity (>90% even at high temperatures above 325 °C) for Ru /Cu-CHA during practical ammonia elimination in the presence of NO and water vapor.