Catalytic deactivation mechanism research over Cu/SAPO-34 catalysts for NH3-SCR (II): The impact of copper loading. (31st August 2017) - Tang, Jiaojiao
Graphical abstract: Highlights: Lower copper (<1.7%) loading ensured structure durability even after 950 °C aging. Higher copper loading (>3.91%) accelerated structure collapse after 950 °C aging. The optimal copper loadings for activity and stability didn't overlap. More vacant Brønsted acid site and less copper oxides benefited samples durability. Abstract: Four Cu/SAPO-34 samples by one-pot method are utilized to examine their durability after 950 °C hydrothermal treatment and its relation with copper loading. The SCR results show fresh Cu/SAPO-34 with 3.91% copper loading (F-Cu-3.91) performs the superior NO conversion, wide temperature window and excellent nitrogen selectivity among fresh samples, and NO conversion is mainly determined by isolated Cu 2+ contents at low temperature. After 950 °C aging treatment, Cu/SAPO-34 catalysts with copper loading under 1.70% present good stability, while the ones with copper loading above 3.91% show activity and crystallinity decline. Ex-situ DRIFTs, XRD and NH3 -TPD results reveal the 950 °C aging process leads to Si-OH-Al bonds breakage and phase transition of chabazite support over Cu/SAPO-34 samples with high copper loading, meanwhile, the EPR and TPR outcomes prove the copper oxides' further dispersion and coordination variation due to skeleton collapse. Finally, this work is trying to manifest the appropriate copper loading for a stable Cu/SAPO-34 catalyst and its deactivation mechanism during extreme working situation.