Molecular simulation of adsorption and separation performances for CO2/CH4 mixtures in graphene/nanotube hybrid structures

Abstract

The adsorption and separation behaviors of CO2 and CH4 binary mixture in graphene/nanotube hybrid structures (GNHSs) are investigated by grand canonical Monte Carlo (GCMC) combined with molecular dynamics (MD) simulations. CO2 is preferentially adsorbed in the adsorbents. Compared with a (6, 6) SWCNT (single walled carbon nanotube), GNHSs show improved separation performance. As the temperature rises, the loading of CO2 reduces rapidly while the loading of CH 4 first increases before being reduced. Finally, the kinetic parameters of CO2 and CH4, such as self-diffusivity and residence time, are calculated by MD simulation. The CO2 molecules diffusing in the GNHS need to overcome a higher barrier relative to that for CH4. The diffusion of the two components in the adsorption layer outside of adsorbent also influences the separation of the mixture.