DOUBLE-ROTATION AL-27 NMR-STUDIES OF THE ALUMINOPHOSPHATE MOLECULAR-SIEVE ALPO4-11

Al-27 double-rotation (DOR) NMR experiments have been performed on the hydrated and dehydrated molecular sieve AlPO4-11. In combination with MAS NMR and X-ray diffraction, DOR indicates the nature of the phase transition observed when water is adsorbed. In hydrated AlPO4-11, water is strongly attached to approximately 1/5 of the framework aluminium, producing 6-coordinated Al. All five suggested crystallographic sites are hydrated to an equal extent. Because of this, the Al-27 NMR signal due to the 6-coordinated species does not completely narrow upon double-rotation.