Diffusivities of Ar and Ne in carbon nanotubes

Atomically detailed simulations are used to compute the self-diffusivity and transport diffusivity of Ar and Ne through single walled carbon nanotube (SWNT) pores at room temperature. The diffusivities are computed over a range of loadings, corresponding to external equilibrium bulk pressures ranging from 0 to 100 bar. The diffusivities in carbon nanotubes are compared with diffusivities of the same gases in silicalite, a common zeolite, under the same conditions. We find that self-diffusivities are one to three orders of magnitude faster in carbon nanotubes than in silicalite, depending on loading. The transport diffusivities are about three orders of magnitude faster in nanotubes than in silicalite over all loadings studied. The equilibrium adsorption isotherms and computed diffusivities are used to predict fluxes through hypothetical membranes of nanotubes and silicalite. The fluxes for both Ar and Ne are predicted to be four orders of magnitude greater through nanotube membranes than through silicalite membranes of the same thickness.