Design and synthesis of core-shell structured meso-Cu-SSZ-13@mesoporous aluminosilicate catalyst for SCR of NOx with NH3: Enhancement of activity, hydrothermal stability and propene poisoning resistance

• A core-shell structured meso-Cu-SSZ-13@MAS catalyst was firstly prepared.
• The enhancement of SCR activity, hydrothermal stability and poisoning resistance was achieved.
• Mesoporous structure was in favor of the increase of active Cu species.
• High hydrothermal stability was indeed correlated with the MAS shell.
• High propene poisoning resistance was linked to fewer active sites for propene oxidation reaction.

A core-shell structured composite material with a mesoporous aluminosilicate (MAS) shell and mesopore-containing SSZ-13 (meso-SSZ-13) core was first synthesized by combining controlled desilication with subsequent self-assembly. The corresponding catalyst was subsequently prepared by a copper ion-exchange method. This catalyst can simultaneously solve three major problems existing in the previous Cu-SSZ-13 catalyst for NOx emission control from diesel engine exhaust, i.e., low temperature activity, hydrothermal stability and propene poisoning resistance. In comparison with Cu-SSZ-13, the meso-Cu-SSZ-13@mesoporous aluminosilicate (meso-Cu-SSZ-13@MAS) catalyst showed higher SCR activity across the entire temperature range. This increase was observed due to increasing the amount of active Cu species (isolated Cu2+ ions) and fewer pore diffusion limitations. The MAS shell with a “concrete with crushed stone”-like mesostructure could prevent the dealumination of meso-SSZ-13 core effectively, and therefore enhanced the hydrothermal stability of the meso-Cu-SSZ-13@MAS catalyst. Additionally, meso-Cu-SSZ-13@MAS exhibited higher hydrocarbon poisoning resistance because its external surface has fewer active sites for propene oxidation reaction.

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