Adsorption equilibrium of methane on activated carbon and typical metal organic frameworks

To develop adsorbents suitable for the storage of natural gas by adsorption, activated carbon SAC-02, HKUST-1 and MIL-101(Cr) were synthesized and characterized in terms of structural morphology observation, nitrogen physisorption at 77.15 K, and methane adsorption at 293.15–313.15 K and 0–4 MPa. The methane adsorption isotherms were comparatively correlated with the Toth, D-A and Ono-Kondo equations and the performances of the adsorbent samples were evaluated in terms of the isosteric adsorption heat and the adsorbed phase density. The results indicate that in comparison with the D-A and Ono-Kondo equations, the Toth equation displays much smaller relative errors in correlating the methane adsorption data and is then more suitable for the adsorption equilibrium analysis on the adsorbed natural gas (ANG) system. MIL-101(Cr) exhibits the largest mean isosteric heat for methane adsorption and the density of the adsorbed methane phase is smaller than that of the liquid methane but increases with the equilibrium pressure; overall, MIL-101(Cr) with highest adsorption capacity is more suitable for methane adsorption than activated carbon and HKUST-1.