Acetate-Assisted Preparation of High-Cu-Content Cu-SSZ-13 with a Low Si/Al Ratio: Distinguishing Cu Species and Origins

The rational design of high-performance Cu-SSZ-13 catalysts with enhanced low-temperature activity represents a critical challenge for meeting stringent Euro VII emission standards in diesel aftertreatment systems. Elevating Cu loading can theoretically improve catalytic performance; however, one-time ion exchange using common CuSO4 solution makes it hard to accomplish high Cu-ion contents. Herein, we demonstrate that the conventional ion-exchange method, adopting Cu(CH3COO)2 as precursor in NH4-SSZ-13 zeolite with a low Si/Al ratio (≈6–7), can achieve higher Cu content while maintaining superior dispersion of active sites. Comprehensive characterizations reveal a dual incorporation mechanism: canonical Cu2+ ion exchange and unique adsorption of the [Cu(CH3COO)]+ complex. In the latter case, the surface-adsorbed [Cu(CH3COO)]+ ions form high-dispersion CuOx species, while the framework-confined ones convert to active Z[Cu2+(OH)]+ ions. The Cu(CH3COO)2-exchanged Cu-SSZ-13 catalyst exhibits superior low-temperature SCR activity and hydrothermal stability to its CuSO4-exchanged counterpart, making it particularly suitable for close-coupled SCR applications. Our findings provide fundamental insights into Cu speciation control in zeolites and present a scalable, industrially viable approach for manufacturing next-generation SCR catalysts capable of meeting future emission regulations.