Enhancement of nitric oxide reduction via CeZrOx/Cu-SSZ-39 hybrid catalyst: Improving activity and hydrothermal stability

Abstract

This study aimed to improve the catalytic activity and hydrothermal stability of Cu-SSZ-39 zeolite by coupling it with cerium zirconium oxides (CeZrO_x), which possesses excellent oxidizing ability, and a hybrid catalyst CeZrO_x/Cu-SSZ-39 was prepared. It is found that it exhibited enhanced low-temperature activity, high-temperature activity, and a wider effective temperature range compared to Cu-SSZ-39. Characterization results showed that the CeZrO_x/Cu-SSZ-39 catalyst had a higher concentration of active Cu²⁺ ion species and improved redox properties, which could potentially promote the NH₃-SCR reaction. Additionally, the CeZrO_x/Cu-SSZ-39 catalyst had increased chemisorbed oxygen species on its surface, facilitating the oxidation of NO to NO₂ and enhancing the rate of the SCR reaction. Moreover, even after undergoing hydrothermal aging treatment, the CeZrO_x/Cu-SSZ-39 catalyst exhibited superior catalytic activity and improved hydrothermal stability, surpassing the performance of Cu-SSZ-39. It is found the CeZrO_x coupling allowed the hybrid catalyst to maintain a better specific surface area and pore structure during hydrothermal aging, resulting in reduced activity loss. Therefore, the addition of CeZrO_x enhanced the NH₃-SCR activity of Cu-SSZ-39 zeolite, leading to improved catalytic activity and hydrothermal stability. CeZrO_x/Cu-SSZ-39 catalyst has shown promising aspect for reducing NOx emissions from diesel vehicle exhaust.