Molecular Simulation of H2O, CO2, and CH4 Adsorption in Coal Micropores

Аннотация

Based on the chemical model of coal, slit micropores with different pore sizes are established and structures are optimized in the software of materials studio. As the temperature rises, absolute adsorption capacities of H₂O are slightly affected, while absolute adsorption capacities of CO₂ and CH₄ gradually decrease. As the fugacity rises, excess adsorption curves of CO₂ experience increase-decrease-gentle three stages, while the curves of CH₄ gradually decrease. With the increase of pore size, adsorption capacities of H₂O increase, while adsorption capacities of CO₂ and CH₄ gradually decrease. H₂O firstly adsorbs on the oxygen-containing functional group, so the walls of pore are the preferential area for H₂O, while CO₂ and CH₄ choose to adsorb on–C–C–, therefore the walls are the primary area for CO₂ and CH₄. Strong potential in micropores and hydrogen bond among water molecules will promote the water adsorption, while the adsorptions of CO₂ and CH₄ are only induced by the Van der Waals interaction, but the difference between adsorption density and bulk density of CO₂ and CH₄ decides the change of excess adsorption capacity.