Molecular Simulation of Adsorption and Separation Performances for CO2/CH4 Mixtures in Graphene/Nanotube Hybrid Structures

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 CH4 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.