Characterisation of porous silica. 2. CPG-10 (VYCOR)

Porous silica CPG-10 has been characterised by adsorption of benzene before and after modification with trimethylchlorosilane. The Brunauer–Emmet–Teller (BET) specific surface areas were determined where possible. Modification of CPG-10 reduces its adsorption for benzene and hence reduces the BET specific surface area, with the extent of reduction depending on the extent of modification. For a fully modified sample with the highest surface concentration of trimethylsilyl groups, the adsorption isotherm changes from type IV of the unmodified sample to type V. The hysteresis loop size and position are also altered. A mechanism for multilayer adsorption and capillary condensation in modified porous silica is proposed.