ADSORPTION OF CARBON-DIOXIDE, SULFUR-DIOXIDE AND WATER-VAPOR BY MCM-41, A MODEL MESOPOROUS ADSORBENT

Adsorption isotherms of carbon dioxide, sulfur dioxide and water vapour have been determined on a well characterized sample of MCM-41. The shape of the carbon dioxide isotherm (at 195 K) is similar to that given by mesoporous hydroxylated silica, whereas the water isotherm (at 303 K) is of Type V in the IUPAC classification and its shape is therefore indicative of a more hydrophobic behaviour. Isosteric enthalpies of adsorption, calculated from the sulfur dioxide isotherms (at 254 and 273 K), reveal strong energetic heterogeneity in the adsorbent-adsorbate interactions and it appears that the high-energy sites occupy ca. 30% of the total surface area.