Y-Doped Cu-SSZ-39 Zeolite with Only Cu2+-2Z Species: An NH3-SCR Catalyst with Extremely High Hydrothermal Stability

Copper-exchanged SSZ-39 zeolite catalysts have been proven to be more hydrothermally stable than Cu-SSZ-13 catalysts. However, the synthesis of high-silica SSZ-39 zeolites is still a significant challenge. The excess framework Al in Cu-exchanged Al-rich SSZ-39 catalysts leads to not only severe dealumination during hydrothermal aging but also damage to the SCR-active Cu2+ ions by the detached Al. In this work, in-depth knowledge of the stabilization of Al by Y is provided. It was found that the energy needed to break the first Al-O bond is significantly enhanced due to the Y3+ located in the eight-membered rings. Additionally, Cu2+-2Z and Y have a synergistic effect on the stabilization of the framework Al. The introduction of Y into the Cu-SSZ-39 catalyst with hydrothermally stable Cu2+-2Z as the only Cu species remarkably enhanced both the low-temperature activity and the hydrothermal stability. The catalyst maintained excellent deNO(x) activity even after hydrothermal aging at the extremely high temperature of 940 degrees C. Both stable Cu species and stable framework Al are essential for the design of hydrothermally stable Cu-exchanged zeolite catalysts.