Molecular model construction of bituminous coal and its oxygen adsorption characteristics under different moisture conditions

To investigate the oxygen adsorption characteristics of coal with different moisture contents, a molecular model of bituminous coal from Datong coalfield was constructed based on 13C-NMR and XPS analysis, combined with molecular mechanics (MM) and molecular dynamics (MD) methods. The oxygen adsorption characteristics of coal were studied using the Grand canonical Monte Carlo (GCMC) method at a temperature of 293.15 K, with a pressure range of 0-10 MPa, and moisture contents of 3.27%, 5.13%, 6.92%, and 8.65%, respectively. The results show that the molecular formula of the Datong bituminous coal structure model is C159H134O35N2S, with a density of 1.35 g/cm3. High moisture content coal has a lower molecular surface area and porosity, and oxygen adsorption on coal molecules follows type I isotherms. The amount of physical oxygen adsorption decreases with increasing moisture content. The heat of physical adsorption is negatively correlated with pressure, and high moisture content accelerates the decrease in heat of physical adsorption caused by increased pressure.