Study on the Performance of the Zr-Modified Cu-SSZ-13 Catalyst for Low-Temperature NH₃-SCR

Area of Science:

• Catalysis
• Environmental Chemistry
• Materials Science

Background:

• Ammonia selective catalytic reduction (NH3-SCR) is crucial for controlling nitrogen oxide (NOx) emissions.
• Cu-SSZ-13 catalysts are effective for NH3-SCR, but their performance, especially at low temperatures, can be further optimized.
• Zeolite modification offers a pathway to enhance catalytic properties for environmental applications.

Purpose of the Study:

• To investigate the effect of zirconium (Zr) modification on Cu-SSZ-13 catalysts for NH3-SCR.
• To determine the optimal Zr/Cu mass ratio for enhanced catalytic performance.
• To elucidate the structural and chemical changes induced by Zr doping and their impact on catalytic activity.

Main Methods:

• Catalyst preparation using ion-exchange and impregnation methods.
• NH3-SCR performance evaluation using a dedicated catalyst testing device.
• Comprehensive characterization including XRD, ICP-OES, BET, NH3-TPD, H2-TPR, XPS, and in situ DRIFTS.

Main Results:

• Zr-modified Cu-SSZ-13 catalysts exhibited improved NH3-SCR activity, particularly at low temperatures.
• An optimal Zr/Cu mass ratio of 0.2 resulted in nearly 100% NOX conversion at 200 °C and over 80% at 450 °C.
• Zr doping increased acid sites, enhanced Cu species reducibility, and regulated Cu+/Cu2+ ratios, favoring low-temperature SCR.

Conclusions:

• Proper Zr doping significantly enhances the low-temperature activity and broadens the operational window of Cu-SSZ-13 catalysts for NH3-SCR.
• The synergistic interaction between Cu and Zr species is key to improving catalytic performance.
• The modified catalysts provide favorable conditions, including abundant acid sites and dual reaction mechanisms (E-R and L-H), for efficient low-temperature NH3-SCR.