Molecular insights into butane isomer separation by MFI zeolite membrane: Intersection channel effect on the orientation of fluid molecules

MFI zeolite membranes are widely used for separating butane isomers, however, MFI zeolite membranes show significantly different separation performance in butane isomers under different conditions. In this study, molecular simulation combined with the Solution-Diffusion model is used to study the mechanism of MFI zeolite membrane separation on butane isomer. Results demonstrate that the n/i-butane selectivity along the zig-zag channel of MFI zeolite membranes is higher than that along the straight channel and separation performance difference is mainly due to the diffusion contribution. Intersection channel plays an important role in butane isomer diffusion selectivity. The integration of the unfavorable molecular orientation of i-butane at intersections can reflect the change of diffusion coefficient. The diffusion coefficient containing molecular microstructural information combined with the Solution-Diffusion model is further extended to understand the selectivity by highly oriented MFI zeolite membranes under different temperatures (298–373 K) and feed side pressures (101–201 kPa).