Solid-state NMR and powder XRD studies of the structure of SAPO-40 upon hydration–dehydration cycles
Abstract
Upon hydration template-free SAPO-40 shows the opening of certain Si—O—Al and P—O—Al bonds; although 27Al, 31P MAS NMR and powder X-ray diffraction (XRD) suggest that this effect is completely reversible on dehydration, 29Si MAS NMR indicates that the local silicon environments are not fully restored.