Experimental and Modeling Study of Methane Adsorption on Activated Carbon Derived from Anthracite

Low-cost anthracite was used as the raw material for preparing microporosity controlled activated carbons by KOH activation. The adsorption characteristics of methane onto activated carbon were measured at 298 K and pressures up to 3.5 MPa by a volumetric method. The experimental data were fitted to the Dubinin–Astakhov model, and relative deviations of better than 0.1 % were obtained. Three main factors were suggested, accounting for the higher methane uptake. It was revealed that better methane uptake is dependent on larger micropore volume and specific surface area. When the micropore volume and surface area of two samples are similar, the activated carbon possessing a narrower micropore size distribution performed higher methane uptake. The relationship between the surface coverage (C/C 0) and the isosteric heat of adsorption confirmed that the heterogeneities of the as-obtained samples was a main factor influencing the methane adsorption at a surface coverage lower than 0.7. The activated carbon possessing higher heterogeneity deserved better methane uptake. The kinetics of methane adsorption on five activated carbons obeyed the pseudosecond-order equation very well under current experimental conditions (298 K, 0.28 MPa). The activated carbon displayed a faster adsorption rate and possessed a better adsorption capacity of methane.