Understanding the influence of hydrothermal treatment on NH3-SCR of NO activity over Cu -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. Cux-SSZ-16 catalysts were prepared by exchanging SSZ-16 zeolite with Cu and applied for selective catalytic reduction (SCR) of NOx with ammonia. Among these catalysts, Cu2.2-SSZ-16 performs the best SCR denitration (deNOx) performance that above 90% NOx 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 Cu2.2-SSZ-16 catalyst are investigated in detail by various characterization methods including XRD, SEM, H2-TPR, NMR, UV–vis-DRS, EPR, NH3-TPD and in situ DRIFTS. Cu2.2-SSZ-16 still shows good NH3-SCR activity after hydrothermal aging at 650 and 750 °C due to more Cu2+-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, Cu2.2-SSZ-16 is a competitive candidate for NH3-SCR deNOx reaction in practical applications.