Adsorptive separation studies of ethane-methane and methane-nitrogen systems using mesoporous carbon

Adsorptive separations of C₂H₆/CH₄ and CH₄/N₂ binary mixtures are of paramount importance from the energy and environmental points of view. A mesoporous carbon adsorbent was synthesized using a soft template method and characterized with TEM, TGA, and nitrogen adsorption/desorption. Adsorption equilibrium and kinetics of C₂H₆, CH₄, and N₂ on the mesoporous carbon adsorbent were determined at 278, 298, and 318K and pressures up to 100kPa. The adsorption capacities of C₂H₆ and CH₄ on the mesoporous carbon adsorbent at 298K and 100kPa are 2.20mmol/g and 1.05mmol/g, respectively. Both are significantly higher than those of many adsorbents including pillared clays and ETS-10 at a similar condition. The equilibrium selectivities of C₂H₆/CH₄ and CH₄/N₂ at 298K are 19.6 and 5.8, respectively. It was observed that the adsorption of C₂H₆, CH₄, and N₂ gases on the carbon adsorbent was reversible with modest isosteric heats of adsorption, which implies that this carbon adsorbent can be easily regenerated in a cyclic adsorption process. These results suggest that the mesoporous carbon studied in this work is a promising alternative adsorbent for the separations of C₂H₆/CH₄ and CH₄/N₂ gas mixtures.