Simulation of methane permeability in carbon slit pores

Abstract

Using a one-site spherical CH₄ molecular model, we predict permeabilities in carbon slit pores of width 0.65-0.75 nm, based on adsorption isotherms obtained from grand canonical Monte Carlo (GCMC) simulation and diffusivities from equilibrium molecular dynamics (EMD). In the range of temperature of 298-318 K and pressure of 0.01-80 bar, the permeability within the slit pore is more strongly influenced by adsorption isotherms than by diffusion. It is found that the permeabilities predicted by the slit pore model far exceed those experimentally measured in practical membrane systems, consistent with our recent observations based on simulations of carbon dioxide permeability in slit pores. These results suggest that the pore entrance resistance (or pore mouth barrier), not considered in simulations of transport in semi-infinite slit pores, may be a dominating factor in nano-porous membrane transport.