Destructive and Protective Effects of NH3 on the Low-Temperature Hydrothermal Stability of SAPO-34 and Cu-SAPO-34
- Ma, Yue
- Gao, Yang
- Wu, Xiaodong
- Jin, Baofang
- Ran, Rui
- Si, Zhichun
- Weng, Duan
DOIAbstract
The influences of gaseous, weakly adsorbed, and strongly adsorbed NH3 on the low-temperature (<100 degrees C) hydrothermal stability of SAPO-34 and Cu-SAPO-34 were investigated. NH3 temperature-programmed desorption (NH3-TPD), H-1 magic angle spinning nuclear magnetic resonance (MAS NMR), and diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) were adopted to characterize the adsorption states of NH3 and H2O in SAPO-34, and the destruction of the SAPO-34 framework was revealed by direct and cross-polarization Si-29, Al-27, and P-31 MAS NMR. Gaseous NH3 coadsorbed with H2O inside SAPO-34 micropores and induced the hydrolysis of framework P-O-Al and Si-O(H)-Al bonds. Weakly adsorbed NH3 was released during aging and played a ...
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