Insight into the role of Na distribution in Cu-SSZ-39 catalysts

Abstract

Cu-SSZ-39 has garnered significant attention because of its outstanding NH₃-SCR activity and hydrothermal stability. To facilitate commercial application of Cu-SSZ-39, it is crucial to streamline the synthesis process, adopt eco-friendly synthesis methods, enhance the catalytic performance, and explore the underlying catalytic mechanisms. Herein, ammonia exchange was skipped and Cu-SSZ-39 was directly synthesized via Cu-exchange of Na-SSZ-39. This approach yielded a Cu-SSZ-39 with superior catalytic performance compared to that prepared using the conventional NH₄-SSZ-39. Comparative characterization of the Cu-SSZ-39 catalysts, derived from both Na-SSZ-39 and NH₄-SSZ-39 exchanges demonstrated that the positioning of Na cations affected Cu distribution, and controlling Na distribution can enhance deNO_x activity. It was also found that while cation locations did not alter the reaction mechanism of Cu-SSZ-39 at low temperature, they did increase the concentration of active NO_x intermediates, thereby boosting catalytic performance. This study facilitates a more sustainable synthesis of Cu-SSZ-39 and provides deeper insights into how cations’ distribution in zeolites affects catalytic efficiency.