Rapid Transport of Gases in Carbon Nanotubes

Abstract

We report atomistic simulations for both self- and transport diffusivities of light gases in carbon nanotubes and in two zeolites with comparable pore sizes. We find that transport rates in nanotubes are orders of magnitude faster than in the zeolites we have studied or in any microporous material for which experimental data are available. The exceptionally high transport rates in nanotubes are shown to be a result of the inherent smoothness of the nanotubes. We predict that carbon nanotube membranes will have fluxes that are orders of magnitude greater than crystalline zeolite membranes.

A novel algorithm to model the influence of host lattice flexibility in molecular dynamics simulations: Loading dependence of self-diffusion in carbon nanotubes

“…18, 23, and 38-45͒ by means of molecular simulations. A particularly interesting observation is the remarkable increase in the diffusion coefficient of simple molecules at low densities observed by Skoulidas et al 10 These molecular simulations predicted a diffusion coefficient higher than the corresponding gas phase value. This pronounced increase was subsequently reproduced by other groups 17,18 and explained in terms of the smoothness of the nanotube.…”

“…It is therefore of practical interest to understand the diffusive behavior of molecules adsorbed in these materials. [10][11][12][13][14] The adsorption capacity and the fast diffusion of guest molecules inside CNTs were the motivations for studies of diffusion [10][11][12] and adsorption in CNTs ͑Refs. 18, 23, and 38-45͒ by means of molecular simulations.…”

Gas Transport Characteristics through a Carbon Nanotubule

“…Molecular dynamics simulations have suggested that carbon nanotubes, with diameters on the order of a nanometer, will have excellent separation properties due to their size 23 and higher throughputs than similarly sized materials due to their smoothness. 24 While the nanotubules studied here probably do not have the same molecular structure as carbon nanotubes, they do experimentally display a higher throughput due to the carbon coating on their surface. Further experiments need to be performed to determine if this throughput enhancement will apply to carbon nanotubes, though the combination of these results and MD simulations are a favorable suggestion in this direction.…”

The Separation Power of Nanotubes in Membranes: A Review

“…Transport through nanotubes was reported already in 2001 for methane/ethane, methane/n-butane, and methane/ isobutene through single-walled carbon nanotubes [145], and in 2002 for gases [146]. Water transport through carbon nanotubes was considered by Joseph and Aluru [147], who further elaborate the effect of smoothness of the CNT surface on water transport.…”