Unveiling the support effect in Pt-based catalysts for the selective catalytic oxidation of NH3 under realistic diesel engine conditions

Abstract

Pt catalysts have been widely used for the selective catalytic oxidation of NH₃ (NH₃-SCO) in practical applications due to their high activity at low temperatures. However, more stringent regulations require further enhancement of low-temperature NH₃-SCO activity. In this study, we investigated the influence of different supports, including aluminum oxide (Al₂O₃), silica (SiO₂), and chabazite (CHA), on the NH₃-SCO performance of Pt catalysts. Our findings demonstrate that the Pt/CHA catalyst exhibited superior NH₃-SCO performance under realistic diesel engine conditions, characterized by high space velocity and the presence of water vapor. Notably, the Pt/CHA catalyst achieved a significantly lower T₅₀ (temperature at which 50% NH₃ conversion is achieved) of 218 °C under conditions with both CO₂ and H₂O, with a 56 °C reduction compared to the state-of-the-art Pt/Al₂O₃ catalyst. The exceptional NH₃-SCO performance is attributed to the high abundance of metallic Pt⁰ species and the presence of rich and stable acid sites that facilitate NH₃ adsorption and activation. These results highlight CHA as a promising support for the Pt catalyst in NH₃-SCO applications for diesel engine emission control.