Molecular simulation study of adsorption-diffusion of CH, CO and HO in gas-fat coal.

In order to clarify the microscopic dynamics mechanism of CH, CO and HO adsorption and diffusion in coal, and to reveal the mechanism of the influence of different temperatures and pressures on the adsorption and diffusion characteristics of coal adsorbed CH, CO and HO molecules. In this paper, the macromolecular structure model of Jixi gas-fat coal was constructed, based on the Giant Canonical Monte Carlo (GCMC) and Molecular Dynamics (MD) methods. The adsorption-diffusion characteristics of CH,CO and HO single-component gases in the gas-fat coal macromolecule model at temperatures ranging from 273.15 K to 313.15 K and pressures ranging from 0.01 MPa to 15 MPa were investigated by using Material Studio software. The research results indicated that: The adsorption of three gases, CH, CO and HO, increased with the increase of equilibrium pressure, and the adsorption isotherms conformed to Langmuir type I isotherms. The amount of saturated adsorption of CH ranged from 11.18 to 14.37 ml/g, the saturated adsorption of CO ranged from 20.40 to 24.70 ml/g, and the saturated adsorption of HO ranged from 66.61 to 84.21 ml/g. With the increase of temperature, the saturated adsorption of CH and CO both decreased, and the saturated adsorption of HO firstly increased and then decreased, and the adsorption of HO by low temperature and high temperature had both an inhibitory effect on the adsorption of HO. The potential energy distributions of CH, CO and HO molecules are poisson distributed. The absolute values of the most available interaction energies are, from highest to lowest: HO > CO > CH; the activation energies for diffusion of CH, CO and HO are 12.20 kJ/mol, 3.36 kJ/mol, and 8.47 kJ/mol, respectively, and the diffusion of CO is the more likely to occur. The adsorption of CH and CO in coal is physical adsorption, while the adsorption process of HO molecules is beyond the scope of physical adsorption. The absolute value of the interaction energy is HO > CO > CH in descending order.