INTERPRETATION OF ADSORPTION-ISOTHERMS AT ABOVE-CRITICAL TEMPERATURES USING A MODIFIED MICROPORE FILLING MODEL

A new micropore filling model, which has a Henry's law region and predicts an upper limit to micropore size, is applied here to adsorption at supercritical temperatures. Data obtained here on the adsorption of methane and carbon dioxide on activated carbons are interpreted in terms of this model, while utilizing independently obtained pore size distributions. The results show that the contributions of micropore filling and mesopore surface adsorption can vary considerably with temperature as well as adsorbate, because of the dependency of the upper limit of micropore size in which filling occurs on these variables. In light of these findings it appears that concepts such as micropore volume and mesopore surface area are not reliable characteristics of the pore structure as they vary with process conditions.