An investigation was made of the storage and adsorption selectivity of CO2 and CH4 in nanoporous silicalite, IRMOF-1 and C168 schwarzite using Monte Carlo simulations. The self-, corrected and transport diffusivities of CO2 and CH4 were examined using molecular dynamics simulation. The activation energies at infinite dilution were evaluated from Arrhenius fits to the diffusivities at various temperatures. As the loading increased, the self-diffusivities in the 3 frameworks decreased as a result of steric hindrance. The corrected diffusivities remained nearly constant or decreased approximately linearly, depending upon the adsorbate and framework. The transport diffusivities generally increased, except for CO2 in IRMOF-1. Maxwell-Stefan predictions of self-, corrected and transport diffusivities for pure CO2 and CH4 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. On the basis of adsorption and self-diffusivity in the mixture, the permoselectivity was found to be marginal in IRMOF-1, slightly enhanced in MFI and greatest in C168 schwarzite.

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