EVALUATION OF STRUCTURAL HETEROGENEITIES AND SURFACE IRREGULARITIES OF MICROPOROUS SOLIDS

The Jaroniec-Choma (JC) isotherm equation for adsorption of gases and vapors on heterogeneous microporous solids is associated with a gamma distribution function F(z = 1/E0), where z is the inverse characteristic energy that appears in Dubinin-Astakhov (DA) equation. The distribution F(z) characterizes uniquely a microporous solid because its evaluation does not require the knowledge of the relationship between the micropore dimension x and the characteristic energy E0; however, this relationship is necessary to calculate the micropore-size distribution function J(x), which can be obtained easily from the distribution F(z) for any arbitrary relationship x(z). It is shown that the shape of the micropore-size distribution J(x) depends significantly on the relationship x(z), and that the relationship x(z) found experimentally by Stoeckli leads to a decreasing function J(x), which coincides with that obtained for fractally microporous solids over a large region of micropore sizes. The benzene adsorption isotherm on a microporous activated carbon is used to illustrate the proposed procedure for evaluating structural heterogeneities and surface irregularities of microporous activated carbons. © 1990.