PORE-SIZE AND LIQUID IMPREGNATION OF MICROPOROUS ALUMINOSILICATE GELSAND GLASSES

Optically clear monolithic (OCM) gels of microporous aluminosilicates have been prepared by slow hydrolysis-polycondensation of alkoxides. S ubsequent heating induces transformations into OCM microporous glasses . The surface area (similar to 610 m(2)/g after drying at 300 degrees C) and the pore volume (similar to 0.35 cc/g at 300 degrees C) decreas e monotonously with increasing annealing temperature. However, after h eat treatment at 600 degrees C under air (glass state) the monoliths a re still microporous. Modifications of the xerogel pore distribution b y an impregnation process and metal aggregate formation with pyrolysis are studied by N-2 adsorption-desorption analysis and small-angle X-r ay scattering (SAXS). The microporous structure becomes mesoporous. A model of microporous impregnation in the gel or glass state is propose d.