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Adsorption Behavior of Hydrocarbon on Illite

Chen, G., Zhang, J., Lu, S., Pervukhina, M., Liu, K., Xue, Q., Tian, H., Tian, S., Li, J., Clennell, M. B., Dewhurst, D. N.
Energy & Fuels 2016 v.30 no.11 pp. 9114-9121
adsorption, clay, illite, methane, micropores, prediction, surface area, temperature
The adsorption of hydrocarbon (pure CH₄ and C₂H₆) on illitic clay was investigated at temperatures of 333, 363, and 393 K (60, 90, and 120 °C) over a range of pressures up to 30 MPa using grand canonical Monte Carlo (GCMC) simulations. We first discussed the comparability of molecular simulation results with experimental measurements. Our results indicate that molecular simulation results of the excess adsorption are comparable with the experimental measurements if they are both expressed per unit surface area available for adsorption instead of per unit mass. The gas density profiles indicate that the adsorption of CH₄ and C₂H₆ is mainly affected by the clay surface layers. In micropores smaller than 2 nm, the overlapping of the interaction of the simulated pore walls with the gas results in enhanced density peaks. For pore sizes of 2 nm or larger, the overlapping effect is significantly reduced, and the height of the gas density peak close to the surfaces is no longer affected by pore sizes. The maximum excess adsorption of illite for C₂H₆ is almost twice that for CH₄ due to the stronger interaction between illite and C₂H₆ than between illite and CH₄, but the saturation capacity (maximum loading) is the same for both. Our findings may provide some insights into gas adsorption behavior in illite-bearing shales and give some guidance for improving experimental prediction.