ALUMINUM INCORPORATION IN MESOPOROUS MOLECULAR-SIEVES

Aluminosilicate mesoporous materials synthesized with various amounts of aluminum have been characterized by solid-state Al-27 NMR, powder X-ray diffraction, thermogravimetric analysis, scanning electron microscopy, and elemental analysis to determine the extent of aluminum incorporation and its location in the final product. The presence of aluminum in the framework is observed to influence the stability of the structure to calcination. These studies, in combination, establish that four-coordinate aluminum can be incorporated into the inorganic mesoporous framework, provided a monomeric alumina precursor is used in the synthesis. When the aluminum source is colloidal, residual octahedrally coordinated extraframework aluminum occurs in phase-separated amorphous particles. These results support the synthesis mechanism for mesoporous molecular sieves proposed by Monnier et al. and provide new insight towards isomorphous substitution into mesoporous silicate structures.