New Insights into the Unique Operation of Small Pore Cu-Zeolite SCR Catalyst: Overlapping NH ₃ Desorption and Oxidation Characteristics for Minimizing Undesired Products

An operational challenge associated with SCR catalysts is the NH₃ slip control, particularly for commercial small pore Cu-zeolite formulations as a consequence of their significant ammonia storage capacity. The desorption of NH₃ during increasing temperature transients is one example of this challenge. Ammonia slipping from SCR catalyst typically passes through a platinum based ammonia oxidation catalyst (AMOx), leading to the formation of the undesired byproducts NOx and N₂O. We have discovered a distinctive characteristic, an overlapping NH₃ desorption and oxidation, in a state-of-the-art Cu-zeolite SCR catalyst that can minimize NH₃ slip during temperature transients encountered in real-world operation of a vehicle. In this work we show new insights, gained from NH₃ temperature programmed desorption and oxidation experiments, into the Cu-zeolite catalyst functions responsible for the overlap of NH₃ desorption and oxidation characteristics and the impact of hydrothermal treatment on these functions.