Multisite occupancy adsorption on heterogeneous surfaces. Theory and Monte Carlo simulation

A new theoretical model is presented for the study of multisite-occupancy adsorption on heterogeneous surfaces. The model is based on the introduction of a rigorous expression for the Helmholtz free energy of linear adsorbates on a homogeneous one-dimensional lattice into the model presented by Nitta et al. (1991). The theoretical predictions were compared with experimental data for CO, N2 and O2 adsorbed on zeolites 5A and 10X, with results obtained by means of the Monte Carlo method, for adsorption isotherms for 2-mers, 4-mers and 6-mers adsorbed on heterogeneous surfaces with two types of site. It is shown that the model presented represents a significant improvement compared with the original model of Nitta, an improvement most evident for larger sized molecules (4-mers and 6-mers).