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 318 K and pressures up to 100 kPa. The adsorption capacities of C2H6 and CH4 on the mesoporous carbon adsorbent at 298 K and 100 kPa are 2.20 mmol/g and 1.05 mmol/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 298 K 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.

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► High adsorption amount of C2H6 (2.20 mmol/g) and CH4 (1.05 mmol/g) on mesoporous carbon.
► High equilibrium selectivity for C2H6/CH4 (19.6) and CH4/N2 (5.8) on mesoporous carbon.
► Modest isosteric heats of adsorption of C2H6, CH4, and N2 on mesoporous carbon.
► Adsorption kinetics and diffusion time constants.