THERMOGRAVIMETRIC ANALYSIS OF THE POROSITY AT ISOBARIC CONDITIONS

Thermogravimetric analysis was applied to the characterization of the porosity of silica gel. Experimentally obtained curves representing we ight loss of adsorbate against temperature were converted into plots o f the volume loss versus pore radius. The transformation was performed using the Kelvin equation. By differentiation of these curves, the po re size distributions for silica gel at different desorption condition s were calculated. Taking into account the amount of the liquid adsorb ate desorbed above its normal boiling temperature, the total pore volu me of the silica was estimated. The results from the thermogravimetric method are compared with those obtained from nitrogen method. The con sistency of the parameters characterizing the porous structure of sili ca gel obtained by two different methods is satisfactory. From the des orption curves for non-porous silica gel, the surface film thickness o f liquid adsorbate was estimated. (C) 1998 Elsevier Science B.V.