Hydrothermal stability of CuSSZ13 for reducing NOx by NH3

[Display omitted] •Deactivation of CuSSZ13 by aging becomes more severe as the Cu/Al ratio increases.•Cu2+ ions are first exchanged on the sites on D6R (α) before those in the CHA cage (β).•The β/α ratio reveals a rising trend with increasing Cu/Al ratio.•Cu2+ ions on the CHA sites readily agglomerate leading to the formation of CuOx.•Collapse of SSZ13 due to CuOx is the primary cause for the hydrothermal deactivation. The hydrothermal stability of CuSSZ13 catalysts with respect to their Cu/Al ratio has been investigated to understand the deactivation mechanism of their catalytic activity for NO reduction by NH3/SCR. The decline of the deNOx activity due to the hydrothermal aging became more severe as the Cu/Al ratio increased. Results of ESR, H2-TPR and DRIFT studies indicated that the D6R sites are occupied first by Cu2+ ions (α species) up to their accommodation capacity, followed by the occupation of the CHA sites (β species) with the increase in the Cu/Al ratio. The β species agglomerate more readily than α species due to their less stable nature, leading to the formation of CuOx. The CuOx may grow to destroy the zeolite cage and channel, resulting in the collapse of the SSZ13 structure, which is believed to be the primary cause for the hydrothermal deactivation of the CuSSZ13 catalyst.