LIQUID NITROGEN ADSORPTION ISOTHERM ON AEROSIL

Surface atoms of silicon carrying functional groups may exhibit a tendency to achieve coordination numbers greater than four by forming donor-acceptor bonds with electron-donor molecules; therefore, such atoms are considered active centers. Five-coordinate complexes can be preserved even when the surface is partially filled with isolated hydroxyls. Based on the coordination bond mechanism, adsorbed water molecules are protonated and, as a result, they can also participate as active centers. Their release from the surface occurs in the temperature range of 423-723 K