Adsorption of CH4/CO2/N2 by different functional groups in coal

To explore the microscopic mechanism of gas adsorption by different functional groups in coal and provide theoretical support for the prevention and control of coal mine gas disasters, a slit-pore model and fragment model modified by different functional groups were built using Materials Studio software, based on density functional theory and the Monte Carlo method. The adsorption characteristics of seven different functional group models on the gas were analyzed, and the microscopic mechanism of adsorption performance of different functional groups on CH4/CO2/N2 was revealed. The results showed that the order of the electrophilic ability of each functional group fragment followed benzene ring > –OH > –CO > –O–CH3 > –COOH > –CH3 > –CH2–CH3, and the order of nucleophilic ability was benzene ring > –CH2–CH3 > –CH3 > –COOH > –OH > –CO > –O–CH3. After adding different functional groups to the surface of the complete activated carbon, the electrophilic ability and nucleophilic ability decreased. The adsorption capacity was affected by both gas properties and functional group structure. The adsorption heat was not only affected by the adsorption amount but also by the non-uniformity of the adsorbent surface. The oxygen-containing functional groups were beneficial to the adsorption of CO2 gas, and the aliphatic functional groups were committed to the adsorption of CH4 and N2.