Adsorption of methane and ethane into single-walled carbon nanotubes and slit-shaped carbonaceous pores

The adsorption equilibria of methane, ethane and their binary mixture in single-walled carbon nanotubes (SWNTs) and slit-shaped carbonaceous pores were studied by using a Grand Canonical Monte Carlo (GCMC) method. We used a slit-shaped pore for microporous structure of activated carbons and an armchair type of cylindrical pore for SWNTs. Methane was modeled as a spherical Lennard-Jones (LJ) model and ethane as two LJ sites with the unified methyl group. The isotherms of both components in micropore region displayed Type I adsorption by Brunauer et al., which corresponds to unimolecular adsorption. At low pressure the storage capacity of SWNTs for pure components of methane and ethane was higher than that for slit-shaped pore geometries of the same size, and the selectivities of equimolar bulk gas mixture were much higher. GCMC was shown to give good qualitative agreement with Ideal Adsorbed Solution Theory (IAST).