%0 Journal Article %J Journal of the American Chemical Society %D 1991 %T Study of the Aluminophosphates Alpo4-21 and Alpo4-25 by Al-27 Double-Rotation Nmr %A Jelinek, R. %A Chmelka, B. F. %A Wu, Y. %A Grandinetti, P. J. %A Pines, A. %A Barrie, P. J. %A Klinowski, J. %K nuclei %X

Aluminum-27 double-rotation NMR in a magnetic field of 11.7 T distinguishes the extremely distorted five-coordinated aluminum sites in the molecular sieve precursor ALPO4(-21). Upon calcination, ALPO4(-21) transforms to ALPO4(-25), which has two tetrahedral aluminum sites with similar isotropic chemical shifts that cannot be resolved in an 11.7 T field. The two tetrahedral environments, however, have a different quadrupole coupling constants and are distinguished by double rotation at 4.2 T field. The quadrupole coupling constants obtained for these sites indicates that the tetrahedral aluminum environments are less distorted in the hydrated material.

%B Journal of the American Chemical Society %V 113 %P 4097-4101 %8 May 22 %@ 0002-7863 %G English %U ://WOS:A1991FN00500007 %N 11 %M WOS:A1991FN00500007 %! Study of the Aluminophosphates Alpo4-21 and Alpo4-25 by Al-27 Double-Rotation Nmr %R Doi 10.1021/Ja00011a007