Adsorption equilibrium of methane on activated carbon

The adsorption equilibrium of methane on the activated carbon was studied for practical application of adsorbed natural gas(ANG) technology. Activated carbon SAC-02 was selected as an adsorbent, six isotherms of excess adsorption amount of methane were measured at temperature from-10℃ to 40℃ and pressure up to 8 MPa. Parameters of DA equation, Toth equation and Ono-Kondo equation were set by nonlinear fit of adsorption data. Accuracies of the predicted results were evaluated in terms of the relative error between the experimental data and those determined by the equations. Isosteric heats of methane adsorption on the activated carbon were respectively caculated by adsorption isotheres on the absolute amounts and excess amount as well as from DA equation. It showed that the accumulated relative error from Toth equation and DA equation was respectively less than 0.3% and 0.5% where the pressure was higher than 1 MPa. Results also revealed that the isosteric heat of adsorption calculated by DA equation was temperature dependent, and the isosteric heat of adsorption determined by adsorption isosteres from the absolute amount and excess amount as well as the DA equation was about 16.49-18.81 k J·mol~(-1), 17.31-20.24 k J·mol~(-1)and 15.29-21.58 k J·mol(-1),respectively. Conclusions were drawn that Toth equation was suitable for analyzing adsorption equilibrium of methane on the activated carbon, and DA equation was recommendable for calculating the isosteric heat of methane adsorption on the activated carbon.