Features of the Formation of Adsorption Centers of Thermally Modified High-Silica Porous Glasses

The results are presented on studies of the content of Lewis and Brønsted centers on the internal surface of high-silica porous glass (PG) obtained by the through chemical etching of alkali-borosilicate glass with the two-frame structure, including the one modified by an isothermal treatment in an electric furnace in air in the temperature range from 120 to 750°C. The content of the active surface centers is determined by the adsorption of the acid-base indicators with different р K а values. For all samples under investigation, the predominance of hydroxyl groups over siloxane ones is established, which indicates a high degree of surface hydroxylation; and the extreme dependence of the content of surface centers on the heat treatment temperature with the pronounced maximum at 650°C is found.