Pore size distribution of microporous materials using corrected Horváth-Kawazoe models

The Horváth-Kawazoe (HK) model is a widely used method for determining pore size distribution (PSD) in a microporous material from a single adsorption isotherm. However the original model incorrectly estimates the adsorbate-adsorbate interaction energy which causes the model to underpredict the PSD for micropores measuring larger than two adsorbate molecular diameters. An improved estimate for the interaction energy is provided by the corrected HK models of Rege and Yang (2000) for the three pore geometries (slit, cylindrical and spherical). The Rege-Yang models present a more discrete arrangement of sorbate molecules in a micropore which is based on occupation of positions of lowest energy potentials. Moreover, the average interaction energy is calculated by a population-weighted average of the energy potential of the layers rather than by integration. In this work, examples of pore size distributions predicted by the corrected HK models are given for all three pore geometries. The proposed models show a significantly better agreement with crystallographic data as compared to the original models.