The adsorption of CO2 and CO2/CH4 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 CO2 followed the Langmuir model and decreased with an increasing temperature. The excess adsorption of CO2 increased with an increasing pressure until the pressure reached 3 MPa and then decreased at different temperatures. The S C O 2 / C H 4 decreased logarithmically with increasing pressure, and the S C O 2 / C H 4 was lower with a higher temperature at the same pressure. The interaction energy between CO2 and kaolinite was much higher than that between CH4 and kaolinite at the same pressure. The interaction energy between the adsorbent and adsorbate was dominant, and that between CO2 and CO2 and between CH4 and CH4 accounted for less than 20% of the total interaction energy. The isothermal adsorption heat of CO2 was higher than that of CH4, indicating that the affinity of kaolinite to CO2 was higher than that of CH4. The strong adsorption sites of carbon dioxide on kaolinite were hydrogen, oxygen, and silicon atoms, respectively. CO2 was not only physically adsorbed on kaolinite, but also exhibited chemical adsorption. In gas-bearing reservoirs, a CO2 injection to displace CH4 and enhance CO2 sequestration and enhanced gas recovery (CS-EGR) should be implemented at a low temperature.
Keywords: Monte Carlo simulations; competitive adsorption; kaolinite; temperature.