Diffusion behaviors of binary mixtures of alkanes and aromatics through ZSM-5 zeolite: A kinetic Monte Carlo study

Diffusion of hydrocarbon species in an MFI-type zeolite was investigated using a coarse-grained approach combined with Kinetic Monte Carlo (KMC) simulations. The model was employed to capture and isolate the essential characteristics of hydrocarbon diffusion such as molecular pushing, passing, and blocking. A modified Lennard-Jones type forcefield was used to approximate interactions between molecules, and molecules with the oxygen in the zeolite lattice. The basis for the rate expressions is configurational diffusion theory, which has been adjusted to account for an accurate representation of the motions of hydrocarbon molecules trapped in the zeolite. Diffusion coefficients were estimated for low and high loading of single hydrocarbons as well as binary mixtures. In all cases studied, reasonable agreement was achieved with reported experimental data and molecular dynamics simulations. The model is conceptualized as an analytical tool that may be used to address key engineering topics such as applications of zeolites as size-selective barriers.