Y-Doped Cu-SSZ-39 Zeolite with Only Cu<sup>2+</sup>-2Z Species: An NH<sub>3</sub>-SCR Catalyst with Extremely High Hydrothermal Stability
Jinhan Lin, Xueyang Hu, Xuechao Tan, Chunxi Lin, Yan Zhang, Wenpo Shan, Hong He
Abstract
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 Cu 2+ 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 Y 3+ located in the eight-membered rings. Additionally, Cu 2+ -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 Cu 2+ -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 °C. Both stable Cu species and stable framework Al are essential for the design of hydrothermally stable Cu-exchanged zeolite catalysts.