Effect of Pressure and Temperature on CO(2)/CH(4) Competitive Adsorption on Kaolinite by Monte Carlo Simulations

The adsorption of CO(2) and CO(2)/CH(4) mixtures on kaolinite was calculated by grand canonical Monte Carlo (GCMC) simulations with different temperatures (283.15, 293.15, and 313.15 K) up to 40 MPa. The simulation results show that the adsorption amount of CO(2) followed the Langmuir model and decreased with an increasing temperature. The excess adsorption of CO(2) increased with an increasing pressure until the pressure reached 3 MPa and then decreased at different temperatures. The [Formula: see text] decreased logarithmically with increasing pressure, and the [Formula: see text] was lower with a higher temperature at the same pressure. The interaction energy between CO(2) and kaolinite was much higher than that between CH(4) and kaolinite at the same pressure. The interaction energy between the adsorbent and adsorbate was dominant, and that between CO(2) and CO(2) and between CH(4) and CH(4) accounted for less than 20% of the total interaction energy. The isothermal adsorption heat of CO(2) was higher than that of CH(4), indicating that the affinity of kaolinite to CO(2) was higher than that of CH(4). The strong adsorption sites of carbon dioxide on kaolinite were hydrogen, oxygen, and silicon atoms, respectively. CO(2) was not only physically adsorbed on kaolinite, but also exhibited chemical adsorption. In gas-bearing reservoirs, a CO(2) injection to displace CH(4) and enhance CO(2) sequestration and enhanced gas recovery (CS-EGR) should be implemented at a low temperature.