Solid-State NMR Study of Magnesium Incorporation in Aluminophosphate of Type 20

Magnesium aluminophosphate of type 20 (sodalite structure) was synthesized with two different levels of metal substitution. The amount of Mg from the gel entering into the crystal framework upon hydrothermal treatment varied to maintain Mg ordering in the lattice. The occluded tetramethylammonium hydroxide molecules could not be removed when the structure contained > 1 Mg/sodalite cage. At 1 Mg/sodalite cage, calcination resulted in the partial removal of Mg into the extraframework sites. Nevertheless, the calcinedmaterial contained two different bridging hydroxyl groups located at P(2Al,2Mg) and P(3Al,1Mg) sites corresponding to resonances at -19.3 and -27.7 ppm in the {sup 31}P spectrum, respectively. 15 refs., 6 figs., 2 tabs.