Comparison of the Structure and Porous Texture of Alumina Gels Synthesized by Different Methods

Alumina gels are synthesized by different methods. Those methods include the drying of xerogels by simple evaporation either in water or in an another solvent, the supercritical drying either in alcohol at 260 °C or in CO 2, after hydrolysis in an organic solvent in order to make aerogels, and the supercritical drying either in methanol or in CO 2, after hydrolysis in excess water followed by exchange of the initial water for another organic solvent. These three different synthesis procedures result in different pore textures, from micropores to mesopores, which had different resistance to elimination by sintering during heat treatment up to 1200 °C. Xerogels with micropores in a planar texture configuration keep the smallest residual specific area at 1200 °C, while aerogels hydrolyzed in an organic solvent with a random network of mesopores keep a higher residual specific surface area at the same temperature.