To study methane adsorption on graphite in a wide range of coverages and temperatures, we compare experimental results with Monte Carlo simulations (MCSs) of the grand canonical ensemble (GCE) and mean-field approximation (MFA) of the lattice gas model (LGM). MCSs were performed by employing two models for the substrate description; we utilized Steele's 10-4-3 analytical potential, and as a second approach, we represented the graphite surface as composed of several graphene layers (at the atomic level). We obtained adsorption isotherms and density profiles that confirm a layer-by-layer mechanism at low temperatures; the later results in the analytical model having a denser condensed phase than the atomistic one. LGM calculations show a close-packed lattice configuration and also allow us to describe the adsorption mechanism changes with temperature. The isosteric heat of adsorption that was found was approximately 13 kJ/mol. We can also conclude that, in spite of the greater computational cost, the atomistic model could be employed for surfaces that are not necessarily homogeneous and beyond the low-pressure range that are not covered by the simple, fast description given by the analytical model.

Physical adsorption of SO 2 on exfoliated graphite is studied using classical adsorption volumetry and Monte Carlo computer simulations. The experimental isotherms have been obtained in a wide temperature range to determine the critical temperature for the completion of several layers. The computer simulations are in good agreement with the experimental data. The adsorption potential is analyzed and the results are employed to interpret the distributions of adsorbed molecules according to the gas-solid energy. The adsorbed phase exhibits a certain degree of order in an incommensurate phase with respect to the graphite surface. From the simulations, the structure of the adsorbed phase is analyzed, and the unit cell edge length is estimated.

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