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RESEARCH PRODUCT

Contribution to the study of framework modification of SAPO-34 and SAPO-37 upon water adsorption by thermogravimetry

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Abstract The adsorption–desorption of water vapor in SAPO-34 and SAPO-37 is followed in isobar conditions ( P H 2 O =17.6 mbar ) by thermogravimetry at temperatures from 20°C to 400°C. The phenomenon is reversible in SAPO-34 but not in SAPO-37. The rise in water uptake is the highest at around 60–70°C, i.e. in range where an attack of the frameworks was previously reported. The reversibility (or not) of water adsorption–desorption uptake is linked to this reversible (or not) framework modification. The kinetics of desorption in SAPO-34 is strongly slowed down between 40°C and 60°C. This suggests that the full restructuration of the framework requires some time (700 min in the experimental conditions used). The morphology of the crystals of the two SAPOs is unchanged upon hydration but template-free SAPO-34 crystals become progressively destroyed in the electron beam of an electron microscope.