Unveiling the Promoting Effects of Zr and the Hydrothermal Treatment on the NH3-SCR Activity of the Cu-SAPO-18 Catalyst.

Selective catalytic reduction of NOx by NH3(NH3-SCR) remains challenging for diesel vehicles due to the complex exhaust condition. Cu-SAPO-18 zeolite has emerged as an efficient catalyst for the NH3-SCR process, attributed to its unique small pore configuration and high NH3-SCR activity. Herein, Zr-modified Cu-SAPO-18 has been fabricated and evaluated for the reduction of NOx. The addition of Zr to Cu-SAPO-18 led to enhanced activity, with the 0.05 wt % Zr-doped Cu-SAPO-18 catalyst achieving more than 90% NOx conversion across a temperature span of 230 to 470 °C. More importantly, hydrothermal aging at 750 °C further enhanced the activity significantly, achieving nearly 100% NOx conversion at 175 °C. The presence of Zr led to an increased amount of Cu2+ species and acid sites, while the hydrothermal treatment promoted a significant increase in acidity and facilitated the conversion of some Cu2+ to CuxOy species, which is crucial for the enhanced activity. The present research provides insights into the development of high-efficiency small-pore zeolite-based NH3-SCR catalysts, offering valuable implications for both fundamental research and industrial catalysis.