Understanding the influence of hydrothermal treatment on NH3-SCR of NOx activity over Cux-SSZ-16
SSZ-16 zeolite with AFX topology was synthesized by hydrothermal method using 1,4-diazabicyclo[2.2.2]-octane-C4-diquat dibromide as organic structure directing agent. Cu x -SSZ-16 catalysts were prepared by exchanging SSZ-16 zeolite with Cu and applied for selective catalytic reduction (SCR) of NO x with ammonia. Among these catalysts, Cu 2.2 -SSZ-16 performs the best SCR denitration (deNO x ) performance that above 90% NO x conversion can be achieved at 175–600 °C. Especially, the influences of the hydrothermal aging at various temperatures (650, 750 and 850 °C) on active species and AFX framework of the Cu 2.2 -SSZ-16 catalyst are investigated in detail by various characterization methods including XRD, SEM , H 2 -TPR, NMR, UV–vis-DRS, EPR, NH 3 -TPD and in situ DRIFTS . Cu 2.2 -SSZ-16 still shows good NH 3 -SCR activity after hydrothermal aging at 650 and 750 °C due to more Cu 2+ -2Z species in the sample. Still, obvious deactivation can be observed after hydrothermal aging at 850 °C because of the collapse of AFX skeleton and the weak interaction between active Cu species and the skeleton. Nevertheless, Cu 2.2 -SSZ-16 is a competitive candidate for NH 3 -SCR deNO x reaction in practical applications.
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