A. Wolker et al., SYNTHESIS AND STRUCTURAL CHARACTERIZATION OF MIXED ALUMINUM-GALLIUM-OFFRETITES, Solid state nuclear magnetic resonance, 9(2-4), 1997, pp. 143-153
A new synthesis procedure is reported for the preparation of mixed Al,
Ga-offretites over the entire solid solution range 0 less than or equa
l to Ga/(Ga + Al) less than or equal to 1. The resulting materials are
characterized by X-ray powder diffraction, adsorption microcalorimetr
y and multinuclear solid state NMR. The Si-29 MAS-NMR data are consist
ent with statistical occupancy of the T-1 and T-2 sites by aluminum an
d gallium, and also show no positive evidence for preferential siting
effects between both framework metals. Isotropic chemical shifts and n
uclear electric quadrupolar coupling constants for Al-27 and Ga-71 hav
e been obtained from a field-dependent analysis of the center of gravi
ty in the MAS-NMR spectra, H-Al,Ga-offretites produced by ammonium exc
hange and subsequent calcination reveal evidence of partial demetallat
ion of the framework with formation of extra-lattice metal species. (C
) 1997 Elsevier Science B.V.