Novel Cu-Based CHA/AFI Hybrid Crystal Structure Catalysts Synthesized for NH₃‑SCR

Cu/SAPO-34/5 catalysts were prepared by a traditional hydrothermal/impregnation method to investigate the effect of SAPO-34/5 on deNO_x performance over Cu/SAPO-34/5 (the proportion of SAPO-34/SAPO-5 calculated by its main diffraction peak intensity). These characteristic results prove the fact that the superior deNO_x performance of Cu/SAPO-34/5(3.16) is due to its most abundant Brønsted (B) acid sites and active isolated Cu²⁺. A higher amount of B acid sites over SAPO-34/5(3.16) is better to disperse and stabilize the isolated Cu²⁺ species. Besides, kinetic analysis on as-synthesized Cu/SAPOs catalysts confirms that the hybrid crystal structure of SAPO-34/5 does not change the reaction mechanism for selective catalytic reduction with NH₃ (NH₃-SCR). This work provides a new route to synthesize a novel zeolite NH₃-SCR catalyst for eliminating NO_x emitted from diesel engines.