Progressive regulation of Al sites and Cu distribution to increase hydrothermal stability of hierarchical SSZ-13 for the selective catalytic reduction reaction

Abstract

As a commercial catalyst for selective catalytic reduction of nitrogen oxides (NOx) with ammonia (NH3), hydrothermal stability is critical to the lifetime of copper-based SSZ-13. Adjusting the appropriate distribution of framework Al sites and the active copper ions can improve the hydrothermal stability of Cu-SSZ-13. Here we present a hierarchical SSZ-13 catalyst that prepared by the collaborative effect of two organic templates. The employ of C16H33-[N+-methylpiperidine] (C16MPBr) successfully introduced the hydrophobic mesoporous system into the catalyst. Detailed characterizations illustrate that the density of paired Al in the SSZ-13 framework increased with increasing content of C16MPBr in the crystalline gels. The increase in the content of paired Al conversely promotes the generation of more hydrothermally stable Cu2+-2Z species in the six-membered rings sites. This effectively suppresses the loss of active copper ions and dealumination of the framework during the hydrothermal aging, therefore, the hydrothermal stability of the catalyst is remarkably improved.