Pore size analysis by nitrogen adsorption and thermal desorption

Thermogravimetric analysis was applied to the characterization of the porosity of silica gel. Thermal desorption of liquids from silicas for column chromatography was measured. Benzene, n-hexane and carbon tetrachloride were used as liquid adsorbates. Pore size distributions for silica gels of differentiated porosity were determined on the basis of thermogravimetric curves using the Kelvin equation. Pore dimensions were corrected in respect to the surface film thickness estimated from adsorption isotherms of the same adsorbates measured above their boiling point. The resulting pore size distributions and total pore volumes were compared with those obtained from the nitrogen method.