Adsorption Behavior of Methane on Kaolinite

In this work, the adsorption behaviors of CH 4 in slit-like kaolinite pores were investigated using the grand canonical Monte Carlo method. The research results show that the isosteric heat of adsorption of CH 4 decreases with increasing pore size and that CH 4 adsorption on kaolinite can be characterized as physical adsorption. The potential energy between CH 4 and kaolinite was found to decrease with increasing pressure or decreasing pore size, indicating that the adsorption sites of CH 4 changed from higher-energy adsorption sites to lower-energy adsorption sites. The CH 4 adsorption capacity decreased with increasing pore size in mesopores. With increasing temperature, the isosteric heat of adsorption of CH 4 decreased, and the adsorption sites of CH 4 changed from higher-energy adsorption sites to lower-energy adsorption sites, resulting in a decrease of the CH 4 adsorption capacity. As a result of van der Waals force interactions, Coulomb force interactions, and hydrogen-bonding interactions, the water molecules in the kaolinite pores occupies the pore walls in a directional manner, causing the water molecules in the kaolinite pores to accumulate. With increasing accumulation of water, the water molecules occupied adsorption spaces and adsorption sites of CH 4, leading to a decrease of the CH 4 adsorption capacity. The gas adsorption capacity on kaolinite was found to decrease in the following order: CO 2 > CH 4 > N 2 . With increasing mole fraction of N 2 or CO 2, the mole fraction of CH 4 in the gas phase decreased, the adsorption sites of CH 4 changed, and the adsorption space of CH 4 decreased, resulting in a decrease of CH 4 adsorption capacity.