MFI zeolite is one of the most attractive molecular sieve materials for selective adsorption and separation of C4 hydrocarbon isomers. Grand Canonical Monte Carlo and molecular dynamics simulations were used to explore the correlation between the channel structure, adsorption thermodynamics, and kinetic behavior of butane isomers. The results of single component and binary competitive adsorption isotherms of n-butane/i-butane at 273 K, 303 K, 343 K, and 373 K showed excellent low pressure loading and adsorption selectivity for n-butane on MFI zeolite. Density distribution maps and Radial Distribution Function data revealed different preferential adsorption sites for n-butane and i-butane molecules in MFI zeolite. Because of van der Waals repulsion, the adsorption energy of i-butane is less than that of n-butane, making i-butane less apt to be adsorbed in the sinusoidal and straight channels but preferentially in the cross channel of MFI zeolite. Additionally, the mean square displacement and the calculated diffusion coefficient showed that the diffusion rate of n-butane is faster than that of i-butane by more than two orders of magnitude. These findings clarify the molecular mechanism of selective adsorption and separation of n-butane/i-butane on rationally designed MFI zeolite-based materials.

MFI沸石是用于选择性吸附和分离C4烃异构体最有吸引力的分子筛材料之一。使用大正则蒙特卡罗和分子动力学模拟来探索丁烷异构体的通道结构、吸附热力学和动力学行为之间的相关性。正丁烷/异丁烷在273 K、303 K、343 K和373 K的单组分和二元竞争吸附等温线的结果表明，MFI沸石对正丁烷具有优异的低压负载和吸附选择性。密度分布图和径向分布函数数据揭示了 MFI 沸石中正丁烷和异丁烷分子的不同优先吸附位点。由于范德华排斥作用，异丁烷的吸附能小于正丁烷，使得异丁烷不易吸附在MFI沸石的正弦孔道和直孔道中，而优先吸附在交叉孔道中。此外，均方位移和计算的扩散系数表明，正丁烷的扩散速率比异丁烷快两个数量级以上。这些发现阐明了合理设计的 MFI 沸石基材料上正丁烷/异丁烷选择性吸附和分离的分子机制。