Diffusion of N 2 , O 2 , H 2 S and SO 2 in MFI and 4A zeolites by molecular dynamics simulations

At high loadings and temperatures, the order of self-diffusivity of guests in two zeolites is O 2 > N 2 > H 2 S>SO 2 . The diffusion behaviour is different in different zeolites at lower loadings, reflecting different influences from straight channels (MFI) and α-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.