High hydrothermal stability of Cu–SAPO-34 catalysts for the NH3-SCR of NOx

The effects of calcination temperature, Cu source and co-template contents on the activity and hydrothermal stability of Cu–SAPO-34 catalysts prepared by the one-pot hydrothermal synthesis method were investigated. Appropriate calcination temperature was important for the deNOx activity of Cu–SAPO-34 catalyst. The amount of Cu source and co-template in the resulting gel could impact the Cu loading and the crystallization of the final Cu–SAPO-34. Preferably, hydrothermal treatment of the Cu–SAPO-34 catalyst with Cu loading ca. 3.44% at 750 °C for 16 h increased the NH3-SCR activity slightly due to migration of CuO to isolated Cu2+ and the maintenance of the crystallinity as well as the acidity. Moreover, the catalyst aged at 800 °C for 16 h maintained >90% NOx conversion from 225 to 400 °C, and the crystallinity, active Cu2+ species and acidity in Cu–SAPO-34 were not destroyed completely after such harsh treatment. Meanwhile, kinetic analysis over fresh and aged Cu–SAPO-34 samples were conducted and the conclusion were in agreement with the NH3-SCR tests, H2-TPR and NH3-TPD results.