Adsorption separation of CH4/CO2 on mesocarbon microbeads:: Experiment and modeling

A novel meso-porous material, the activated mesocarbon microbeads (a-MCMBs) prepared by this group, is used for the separation of the CH4/CO2 mixture by experiment and modeling. First, the adsorption isotherm of nitrogen at 77K was measured to characterize the a-MCMBs by the IGA-003 gravimetric analyzer. Then, the adsorption experiments of pure CH4 and CO2 at ambient temperature of 298.15 K were carried out. A CH4/CO2 mixture is prepared at the mole ratio of 85:15, corresponding to the gas composition of the Ya-13 gas field in the Qiongdongnan basin, China. Although only the total adsorption amount of the gas mixture on a-MCMBs is available, the single adsorption amount for CH4 and CO2, also including the selectivity Of CO2 over CH4, can be obtained by the Zhou, Gasem, and Robinson Equation of State (ZGR EOS). Finally, the adsorption behavior over a wide range of variables was predicted by the ZGR EOS method. The predicted greatest selectivity of CO2 over CH4 is 3.70 at 3.0 MPa, 258.15 K for the feed gas mole composition of CH4: CO2 = 40:60. Our results demonstrate that a-MCMBs is not only suitable for CH4 storage, but also a promising adsorbent for separation of CH4/CO2. (c) 2005 American Institute of Chemical Engineers.