A molecular simulation study on the adsorption of CH₄ and CO₂ on the mineral substances in oil shale

The models of montmorillonite, kaolinite, calcite and gypsum as the mineral substances in oil shale were built by using Materials Studio 2017 software; the adsorption of CH₄ and CO₂ on these mineral substances was then simulated by the GCMC and MD method. The results illustrated that the adsorption capacity of CH₄ and CO₂ on four mineral substances under the same temperature and pressure follows the order of montmorillonite > kaolinite > gypsum > calcite. The adsorption of single component CH₄ and CO₂ is in accordance with the Langmuir isotherm and the adsorption heats for both CH₄ and CO₂ on four mineral models all are less than 42 kJ/mol, suggesting that the adsorption belongs to physical category. With the increase of temperature, both the adsorption capacity and adsorption heat are reduced; there is a positive correlation between the adsorption heat and adsorption capacity for the CH₄ and CO₂ molecules.