Diffusion of N-2, O-2, H2S and SO2 in MFI and 4A zeolites by molecular dynamics simulations
YX Sun and S Han, MOLECULAR SIMULATION, 41, 1095-1109 (2015).
This paper presents diffusion data of N-2, O-2, H2S and SO2 in MFI and 4A zeolites obtained by molecular dynamics simulations, especially its dependence on temperature and loading. At high loadings and temperatures, the order of self-diffusivity of guests in two zeolites is O-2 >N-2 >H2S>SO2. The diffusion behaviour is different in different zeolites at lower loadings, reflecting different influences from straight channels (MFI) and -cages (4A). Furthermore, with increasing loading, the self-diffusivity of guest molecules decreases in MFI but generally increases in 4A. The centre of mass (COM) probability densities and diffusion trajectories of guests give insight into molecular-level diffusion process. The simulation results reveal that with increasing loading, the diffusion mechanism would change from the inter-pore to intra-pore diffusion in MFI. However, in 4A, the intra- pore diffusion is predominant at low and high loadings, but inter-pore diffusion is more important at moderate loadings.
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