Cold Start Wetting Effect on the Catalytic Property and Hydrothermal Stability of a Cu-SSZ-13 Catalyst for NH3-SCR

The cold start wetting effect on Cu-SSZ-13 has been simulated via soaking catalysts with various Si/Al ratios in ammonium water at disparate pH levels. It is found that a mild treatment (pH = 9) has little effect on the selective catalytic reduction of NOx with NH3 performance of Cu-SSZ-13. However, on increasing the pH to 12, the deNOx activity and resistant ability to hydrothermal aging decrease obviously. Such a decrease could be attributed to the desilication phenomenon during the soaking process, which results in a number of effects including extraction of Cu2+ ions from the exchange sites, decrease in acidity, and damage to the zeolite structure. Meanwhile, the alkaline treatment exhibits distinct impacts on the physicochemical properties of Cu-SSZ-13 with different Si/Al ratios. The low Si/Al ratio catalyst (Si/Al-6) is insusceptible to desilication because of a higher content of the AlO4- structure and extra-framework Al (Alef), which could hamper the desilication.