Adsorption mechanism of CO2/CH4/N2 by the synergistic effect of N/S-doped and functional groups in coal at different temperatures and pressures

Doping-modified coal samples can effectively enhance the adsorption of CO2. In order to investigate the micro-mechanism of the adsorption of different gases by the synergistic effect of N/S atomic doping and functional groups in coal, the microporous constructed by N/S doping with different functional groups in coal at different temperatures and pressures were investigated based on a series of grand canonical Monte Carlo (GCMC) computational simulations. The adsorption amount, heat of adsorption, diffusion coefficient, interaction energy and relative density distribution of CO2/CH4/N2 by the model. It was found that coal samples with more N-doped carboxyl groups could adsorb CO2 better, and coal samples with more N-doped aliphatic functional groups should be selected for adsorption of CH4 and N2, and the N-COOH system had the most stable adsorption state of CO2, and the amount of N-modified coal samples adsorbed CO2 was higher than that of CH4 and N2 at the adsorption temperature of 293.15 K.The diffusion coefficients of the gas molecules showed an increasing trend with the adsorption temperature, and the relative density distributions of CO2/CH4/N2 in the N-doped micropore model were larger than those in the S-doped system. These noteworthy findings provide a valuable theoretical foundation for the advancement of novel adsorbent materials.