Cu-SAPO-18 for NH3-SCR Reaction: The Effect of Different Aging Temperatures on Cu2+ Active Sites and Catalytic Performances

Cu-based silicoaluminophosphate zeolite with an AEI structure (Cu-SAPO-18) was directly synthesized through hydrothermal crystallization. The fresh and aged catalysts were applied for the selective catalytic reduction of NO using NH3. XRD, XPS, H-2-TPR, EPR, BET, SEM, NH3-TPD, and NMR, as well as in situ DRIFTS, are performed to investigate the samples. The results show that different aging temperatures remarkably affect the dispersion of the active sites and catalytic performances. Cu-T-800 exhibits the best NH3-SCR performance, which is attributed to the fact that high-temperature aging decreases the inactive Cu oxides, yet increases the isolated Cu2+. However, under the severe aging temperature of 900 degrees C, Cu-T900 almost has low SCR activity due to the damage of the zeolite framework. The kinetics result indicates that the pore diffusion limitations have a big impact of Cu-F-500. on the NH3-SCR activity, and the aging treatment could decrease the pore diffusion limitations of Cu-F-500.