Lourenço, J. P.Ribeiro, M. F.Ribeiro, F. R.Rocha, J.Gabelica, Z.Derouane, E. G.2012-06-152012-06-151995Lourenço, J. P.; Ribeiro, M. F.; Ribeiro, F. R.; Rocha, J.; Gabelica, Z.; Derouane, E. Thermal and hydrothermal stability of silicoaluminophosphate SAPO-40. Microporous Materials, 4, 445-453, 1995.AUT: JLO01215;http://hdl.handle.net/10400.1/1250Thermal and hydrothermal stability of SAPO-40 were studied by X-ray powder diffraction (XRD) and magic-angle spinning nuclear magnetic resonance (MAS-NMR). For the X-ray study, the hydrothermal treatments were carried out, in situ, in a high-temperature chamber. The SAPO-40 structure shows a remarkable stability to high temperatures under both dry and humid air. At high temperatures a reorganisation of silicon occurs, but the long-range order is only lost above ca. 1000°C. Changes in the XRD pattern induced by water at room temperature are completely reversible upon re-heating at 200°C, as well as the changes in the coordination and local environments of aluminium and phosphorus observed by NMR. For silicon however, some changes, that are observed upon hydration, remain after dehydration.engX-ray diffractionThermal treatmentSAPO-40NMRjournal article2012-06-15