The shape selectivity of zeolites in isobutane alkylation: An investigation using CBMC and MD simulations

Loading-Driven Diffusion Pathway Selectivity in Zeolites with Continuum Intersecting Channels

“…In the presence of different extra-framework ions, the diffusion coefficient of SO 2 slightly decreases in cage-type LTA as the loading increases, whereas it rapidly slows in cage-type FAU, thereby demonstrating the loading effect varies as the extra-framework ions change . When considering the diffusion behavior of 2,2,4-trimethylpentane and 2,4-dimethylhexane molecules with different shapes in FAU or BEA zeolite, the diffusion coefficient of 2,2,4-trimethylpentane is smaller than that of 2,4-dimethylhexane at low loading; however, the reverse is true at high loading . This loading effect is mainly due to the entropy effect caused by the alkane isomer. , Unfortunately, the effect of loading on the anisotropic diffusion was not investigated in these examples.…”

“…31 When considering the diffusion behavior of 2,2,4-trimethylpentane and 2,4-dimethylhexane molecules with different shapes in FAU or BEA zeolite, the diffusion coefficient of 2,2,4-trimethylpentane is smaller than that of 2,4-dimethylhexane at low loading; however, the reverse is true at high loading. 32 This loading effect is mainly due to the entropy effect caused by the alkane isomer. 33,34 Unfortunately, the effect of loading on the anisotropic diffusion was not investigated in these examples.…”

“…Apart from the examples mentioned above, much work has revealed the effect of loading on the diffusion in zeolites, which can be influenced by many factors, such as topology, extra-framework ions, and molecular structure. − For example, the self-diffusion coefficient of methane first increases and then decreases as the loading increases in cage-type LTA zeolite, whereas it monotonically decreases in channel-type AFI or intersecting channel-type MFI zeolites, indicating that topology influences the loading effect . In the presence of different extra-framework ions, the diffusion coefficient of SO 2 slightly decreases in cage-type LTA as the loading increases, whereas it rapidly slows in cage-type FAU, thereby demonstrating the loading effect varies as the extra-framework ions change .…”