Microporous Mg-Si-O and Al-Si-O materials derived from metal silsesquioxanes

Microporous amorphous metallosilicates designated as Mg-Si-O and Al-Si-O, with a very narrow pore size distribution around 6 Angstrom diameter, typical surface areas ranging from 350 to 650 m(2)/g, and loadings of well-dispersed metal oxide (up to about 10 wt % metal) result from the controlled calcination of magnesium and aluminum silsesquioxane complexes [(c-C(5)H(9))(7)Si(7)O(12)](2)Mg(4)Cl(2). 2THF, 1, {[(c-C(5)H(9))(7)Si(7)O(12)]Al}(n), 2, and [(c-C(5)H(9))(7)Si(7)O(11)(OSiMe(3))]- Al[(c-C(5)H(9))(7)Si(7)O10(OSiMe(3))(OH)], 3. Moreover, textural properties such as surface area and pore volume can be easily adjusted by varying the calcination conditions, while the pore size distribution remains practically unchanged. XPS, EDX, solid-state MAS (29)Si and (27)Al NMR, and HRTEM measurements suggest that the metal is present in M-Si-O materials mainly as isolated metal ions incorporated in the amorphous silica framework and also as small crystalline metal oxide particles of a few nanometers, which are well dispersed throughout the silica. SEM was employed as well to evaluate particle size and morphology. IR spectroscopy of adsorbed acetonitrile showed that both Al-Si-O materials are strong Lewis acids. Mg-Si-O and Al-Si-O were briefly tested as catalysts in 1-butanol dehydration. Mg-Si-O gave both dehydrogenation and dehydration, while on Al-Si-O only dehydration and cracking reactions occurred.