Analysis of adsorption kinetics and thermodynamics of methane in shale based on the volume filling theory of micropores

Volume filling of micropores is an adsorption behaviour of adsorbates at higher equilibrium pressures. In this paper, the meaning of the parameters defined in the volume filling theory of micropores is discussed, and the adsorption performance of methane in shale is analysed. Research indicates that it is most appropriate to use the characteristic index curve n = 1 to describe the adsorption behaviour of methane in shale. As adsorption capacity increases, the differential adsorption work (A) will decrease. As the temperature increases, the characteristic energy (E) tends to decrease gradually, and for the case of n = 1, the values of E for shale samples ranged from 4.14 to 5.63 kJ.mol(-1). As the filling rate theta increases, the absolute values of the thermodynamic parameters (Q, Delta H and Delta S) decrease gradually. Under experimental P-T conditions, the values of the thermodynamic parameters change very regularly and do not have mutation characteristics. This indicates that the adsorption energy can be extrapolated under much wider supercritical conditions. We believe that the thermodynamic parameters actually represent the complementarity and comprehensive effects of the TOC and R-o parameters.