Effect of the Adsorbent Pore Structure on the Separation of Carbon Dioxide and Methane Gas Mixtures

The role of the pore structure of the adsorbent in separating CO2/CH4 mixtures was investigated in this study. Three carbon materials with different pore structures, activated carbon (AC), superactivated carbon (Super-AC), and ordered mesoporous carbon (OMC), were used to represent the different porosity characteristics of adsorbents. Some valuable conclusions were obtained via the experiments and analysis: (1) The adsorption capacity and affinity of CH4 are more dependent on the specific surface area and the micropores than those of CO2 at low pressure. (2) When the coverage of CO2 reaches a certain level, the interaction between mesoporous materials and CO2 is stronger than that between microporous materials and CO2. The mesoporous materials can absorb more CO2 than the microporous materials in high pressure. (3) At atmospheric pressure, high specific surface area and micropore volume are adverse to adsorption separation of CO2/CH4 gas mixtures. The mesoporous materials in this work showed higher selectivity at high pressure, and the mesoporous adsorbents have greater potential for separating CO2/CH4 mixtures. (4) In general, the separation performance of adsorbents is slightly affected by the pore structure at atmospheric pressure but controlled by the pore structure at high pressure.