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. [ABSTRACT FROM AUTHOR]