THE AL-27 DOR NMR CHARACTERIZATION OF THE MOLECULAR-SIEVE ALPO4-8

Al-27 double rotation (DOR) NMR spectroscopy has been applied to inves tigate the framework ordering in the aluminophosphate molecular sieve AlPO4-8 during the hydration process. Relative well-resolved peaks in the DOR spectra of both dehydrated and successively rehydrated AlPO4-8 allow the isotropic shifts and the quadrupolar shifts to be correlate d with the local framework structure. The rather complex interaction o f water with AlPO4-8 occurs in a specific way, not randomly. For dehyd rated AlPO4-8 efforts are shown to correlate respectively the isotropi c shifts to the mean Al-O-P angles and the quadrupolar coupling consta nts to the shear strains of the different aluminium sites. (C) 1997 El sevier Science B.V.