Self-diffusivities in multicomponent mixtures in zeolites

Using the Maxwell–Stefan formulation for diffusion in zeolites as a basis, we develop a general analytic expression for the self-diffusivity of a component in a multicomponent mixture. Correlation effects are accounted for by the introduction of particle–particle “exchange” coefficients. Various formulae for estimation of these exchange coefficients have been postulated. The developed procedure for estimation of the self-diffusivity is verified by comparison with kinetic Monte Carlo simulations for binary and ternary mixtures in MFI zeolite and in a square lattice. Additional verification of the analytic model is obtained using published molecular dynamics simulations and experimental data.