Simulating Adsorption and Transport in Hierarchical Zeolites

Hierarchical zeolites are advanced materials possessing the catalytic and adsorption properties of conventional zeolites while potentially eliminating their transport limitations through the introduction of mesopores. Recent experiments comparing the adsorption and transport in hierarchical self-pillared pentasil (SPP) zeolites (SPP) to microporous silicalite-1 (MFI) revealed an interesting crossover in sorbate loading and significantly slower than expected diffusion for alkanes, but explanation for these observations are not readily available through experimental probes due to the complications arising from the presence of multiple adsorption sites and blocked pore entrances. In this talk, we will present results from Gibbs ensemble Monte Carlo and canonical ensemble molecular dynamics simulations to unravel the peculiar properties of SPP zeolites. Computed isotherms for argon, hydrogen, alkanes, ethanol, and water demonstrate striking differences in the adsorption behavior for these adsorbates. Depending on the loading, diffusion can proceed via the micropores, on the mesopore walls, or through the mesopore interior.