Excellent NH3-SCR activity and significant sulfur resistance over novel core–shell Cu-SSZ-13@meso-CeO2 catalyst

Abstract

A core–shell Cu-SSZ-13@meso-CeO2 catalyst with both microporous and mesoporous pores was successfully synthesized using a self-assembly technique in this research. The catalyst was tested via NH3–SCR of NOx removal from diesel exhausts. The Cu-SSZ-13@meso-CeO2 catalyst was found to have significantly improved activity at high temperatures, wider temperature range, improved hydrothermal stability, and anti-sulfur performance. After the introduction of meso-CeO2, a significant synergistic effect between the Cu2+/Ce4+ ions on the core–shell layer was observed, and the amounts of Cu2+–2Z species and acidic sites increased, which may be conducive to the superior catalytic performance of Cu-SSZ-13@meso-CeO2 contrasted to Cu-SSZ-13. Subsequent to hydrothermal treatment, Cu-SSZ-13@meso-CeO2 maintains a superior CHA-type structure, additional L-acidic sites, and isolated Cu2+ ions while being protected by a meso-CeO2 shell. In addition, in the presence of SO2, the meso-CeO2 shell in Cu-SSZ-13@meso-CeO2 reacts with SO2 to produce cerium sulfate, which serves as a protective component for the copper species on Cu-SSZ-13. Moreover, the reaction mechanism studies have indicated that NO reduction primarily adheres to the E–R mechanism on Cu-SSZ-13, whereas both L–H and E–R mechanisms contribute to Cu-SSZ-13@meso-CeO2. SO2 has a less significant inhibitive effect on the adsorption of NH3 over Cu-SSZ-13@meso-CeO2 compared with that over Cu-SSZ-13. The inhibitive influence of SO2 on Cu-SSZ-13@meso-CeO2 is primarily owing to the inhibitory adsorption of NO and the reduction of the L–H reaction path, with little effect on the E–R reaction mechanism, which is significantly affected in Cu-SSZ-13. The Cu-SSZ-13@meso-CeO2 catalyst demonstrated exceptional NH3–SCR performance, a broad temperature range, and super hydrothermal stability as well as anti-sulfur performance, indicating great application prospects for NOx removal from diesel vehicle exhausts.