Distinct effects of Na on Cu-based Beta zeolites for the selective catalytic reduction of NOx with NH3

Abstract

The distinct impact of Na on the NH3-SCR activity of Cu-based Beta zeolites was explored by incorporating Cu onto Na and H-type Beta zeolites via ion-exchange and impregnation methods. The characterization results revealed that an appropriate amount of Na facilitated the exchange of Cu ions into the Beta zeolites, leading to enhanced acidity and NOx adsorption properties. The CuNa-Beta catalysts obtained through ion-exchange, exhibited decreased NH3 oxidation activity at elevated temperatures while demonstrated enhanced NO oxidation activity at lower temperatures, resulting in the improved NOx conversion. However, when the Cu loading was conducted by the impregnation method, Na remained in the Cu/Beta zeolites caused the transformation of Cu to CuOx, resulting in the inferior NH3-SCR performance. These findings demonstrated the significant influence of co-cation Na and preparation methods on Cu locations and NH3-SCR performance of Cu-based Beta zeolites.