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 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 oC 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 Pt catalyst in NH3-SCO applications for diesel engine emission control.