Dual-template-driven in-situ synthesis of Cu-SSZ-39 catalysts: Synergistic structure regulation for excellent NH3 -SCR activity and hydrothermal stability

Abstract

The speciation and distribution of Cu in SSZ-39 Zeolite have a significant influence on its catalytic activity and hydrothermal stability in NH3 -SCR. Herein, we report a dual-template-driven in-situ synthesis strategy to fabricate Cu-SSZ-39 catalysts, where N,N-dimethyl-3,5-dimethylpiperidinium cation (DMDMP + ) and copper ammonia complex (Cu-TETA) collaboratively regulate framework topology and copper speciation. Series of Cu-SSZ-39 catalysts with different Cu content (1.3, 3.6 and 5.8 wt.%) with similar cubic structure were prepared. Unlike conventional post-synthesis ion-exchange methods, this dual-template-driven in-situ synthesis strategy enables the simultaneous crystallization of the SSZ-39 framework and incorporation of isolated Cu 2+ ions at framework Al sites. The DEDMP + template directs the formation of 8-membered ring micropores with enhanced structural crystallinity, while triethylene tetramine (TETA) coordinates with Cu ions to suppress CuO x clusters formation. The dual-template synergy stabilizes [Cu(OH)]⁺ active sites while strengthening acid sites, which collaboratively facilitate the conversion of NO at low temperatures (<250°C). The hydrothermal aging tests demonstrate that the in-situ synthesized catalysts have higher hydrothermal stability, attributed to spatially confined Cu 2+ ions that mitigate dealumination through strong Al-O-Cu bonding. As a consequence, the optimized Cu 3.6 -SSZ-39 catalyst demonstrates exceptional NH3 -SCR performance, achieving >99% NO conversion between 225-525°C (GHSV=60,000 h -1 ) and maintaining >90% initial activity after 750°C for 10 h hydrothermal aging. This work establishes a paradigm for designing hydrothermal-resistant zeolite catalysts through synthesis control of active site architecture, providing critical insights for meeting stricter nitrogen oxide emission standards.