Autoclave treatment effect on silica alcogel texture

The porous texture of silica alcogels prepared under basic or acidic conditions was studied by thermoporometry. Wet gels were subjected to a pressure and temperature at which the solvent becomes a superfluid and then cooled to room temperature. Study of these samples by thermoporometry shows that the thermal treatment results in an increase of mesopore radii and volume and in a disappearance of microporosity. Measurements of the alcogel and aerogel shrinkage allow determination of macroporosity. After heat treatment in the autoclave the latter decreases strongly for gel prepared under acidic catalysis.