Grain size effect on the high-temperature hydrothermal stability of Cu/SAPO-34 catalysts for NH3-SCR

The high-temperature hydrothermal (HTH) stability is always a key factor that affects the NH3-SCR performance and limits the industrial applications of Cu/SAPO-34. Herein, two Cu/SAPO-34 catalysts with different grain sizes are HTH aged to investigate the role of the grain size of Cu/SAPO-34 in holding the structure stability of catalysts and the relationships between the grain size and deNO(x) performance over Cu/SAPO-34 during the HTH treatment. Characterization results illustrates that the relationship between the grain size and the stability of SAPO framework and the content of isolated Cu2+ ions. During the HTH treatment, CuO species more easily transfer to isolated Cu2+ species via migrating into the framework from the external surface of SAPO-34 for the larger-sized catalyst rather than the smaller-sized one. The re-distribution of Cu2+ in the larger-sized catalyst prevents Si-O(H)-Al from H2O attacking during HTH treatment. Therefore, the larger-sized Cu/SAPO-34 maintains stronger structural stability and higher deNO(x) activity than smaller-sized one after HTH treatment. This work provides a new strategy for design of high-temperature hydrothermal stabilized Cu/SAPO-34 for eliminating NOx emitted from diesel engines.