Co-Deactivation of Cu-SSZ-13 Catalyst by K2SO4 Solid-State Diffusion and Hydrothermal Aging

Cu-SSZ-13, the most widely used catalyst in diesel selective catalytic reduction (SCR) systems, often suffers severe deactivation, including hydrothermal aging and ash poisoning. In comparison with traditional impregnation in laboratory work, a more realistic solid-state diffusion method was employed to simulate K2SO4 poisoning on a commercial Cu-SSZ-13 catalyst with high aluminum and copper contents. Hydrothermal aging at 650 °C alone induces severe framework dealumination and transformation of isolated Cu2+ ions to copper aluminate (CuAlOx) species. K2SO4 poisoning alone is more prone to detached Cu2+ ions and aluminum terminal hydroxyl group to form CuSO4 and Al2(SO4)3. The presence of water vapor during K2SO4 poisoning dramatically reduces SCR activity by accelerating the ion-exchange between K+ and Cu2+ and zeolite dealumination. These synergistic effects promote extensive detachment of active Cu species, resulting in the formation of predominating inert sulfates, along with a small amount of CuOx clusters. These findings are expected to provide a theoretical basis for designing catalysts with enhanced resistance to both hydrothermal aging and ash poisoning in diesel aftertreatment applications.