The hydrothermal stability of Cu/SAPO-34 catalysts under different treatment time (3 h, 6 h, 12 h) at 950 degrees C has been investigated to understand their framework collapse and deactivation mechanism for NO reduction by ammonia selective catalytic reduction (NH3-SCR). It was seen that SCR activities declined dramatically after 12 h aging, and XRD results showed this treatment led to crystallinity decline since 3 h. Furthermore, zeolites crystal started to transform into SiO2 and AlPO4 phase since 6 h. NMR results further proved the formation of SiO2 and AlPO4 center dot NH3-TPD and ex-situ DRIFTS results revealed the breakage of Si-OH-Al bonds and the decline of the number of Bronsted acid sites, meanwhile, H-2-TPR and EPR results proved that the number of Cu2+ species decreased and the location of Cu2+ species changed after this treatment, which were mainly responsible for declined SCR reaction rates. (C) 2017 Elsevier Ltd. All rights reserved.