Adsorption of alcohol vapors on alkoxide-derived silica gels

The adsorption behavior of alcohol vapors on acid-catalysed silica gels was investigated. The adsorption isotherms determined at two ambient temperatures were type IV or pseudo type I of BET classification, and were all interpreted by the duplicated processes of multilayer adsorption and capillary condensation. Some of the isotherms obtained gave both the monolayer capacity and the pore volume, which made it possible to calculate the mean pore radii and the fractal dimensions of the pore surfaces. The fractal dimensions obtained were close to 2, indicating the essentially smooth surface on the molecular scale. The gels prepared from the solutions containing smaller alkoxy groups were found to retain larger pore volume, which was explained in terms of the aging effect under acidic conditions.