It was recalled that the storage and adsorption selectivity of CO2 and CH4 in three classes of nanoporous material (silicalite, IRMOF-1, C168 schwarzite) had been investigated using Monte Carlo simulations. The self-, corrected and transport diffusivities of CO2 and CH4 in these materials were examined here using molecular dynamics simulations. The activation energies at infinite dilution were evaluated from Arrhenius fits to the diffusivities at various temperatures. As loading increased, the self-diffusivities in the three frameworks decreased as a result of steric hindrance. The corrected diffusivities remained almost constant, or decreased approximately linearly, depending upon the adsorbate and the framework. The transport diffusivities generally increased, except for CO2 in IRMOF-1. The correlation effects were identified to decrease in accordance with porosity increase. Predictions of the self-, corrected and transport diffusivities for pure CO2 and CH4, in the Maxwell-Stefan formulation, matched the simulation results well. In a CO2/CH4 mixture, the self-diffusivities decreased with loading, and good agreement was found between simulated and predicted results.

Diffusion and Separation of CO2 and CH4 in Silicalite, C168 Schwarzite, and IRMOF-1: a Comparative Study from Molecular Dynamics Simulation. R.Babarao, J.Jiang: Langmuir, 2008, 24[10], 5474-84