Methane adsorption on activated carbon and carbon black

Methane adsorption equilibrium on Ajax activated carbon and graphitized thermal carbon black BP280 above the critical temperature were studied experimentally and theoretically. Isotherms of adsorption were volumetrically measured at 253 K~313 K and 0~20.5 MPa and isosteric heats of adsorption were determined by adsorption isosteres and temperature dependence of Henry's Law constant. An approximate model for adsorption equilibrium was developed and the maximum adsorption capacity was further determined by Langmuir plot of the adsorption model. The interaction energy among the adsorbed methane molecules was obtained by linearization of the model and fitting with the adsorption data. The results showed that the isosteric heats of methane adsorption on activated carbon and carbon black are 11.9 kJ/mol~12.5 kJ/mol and 17.5 kJ/mol~22.5 kJ/mol, respectively; the isosteric heat of adsorption on carbon black varies evenly with the adsorption amount. The maximum adsorption capacity decreases with the increase of temperature; the density of adsorbates is lower than that of liquid methane. The strength of the interaction energy among the adsorbed methane molecules suggests that the adsorbed phase of the supercritical methane is in a state of compressed gas. The adsorption capacity of supercritical methane on a carbon-base adsorbent is largely determined by its specific surface area and micropore volume.