Influence of segregated adsorption on mixture diffusion in DDR zeolite

Abstract

Grand Canonical Monte Carlo simulations for adsorption of CO₂/CH₄, CH₄/N₂, and CO₂/Ar mixtures in DDR zeolite show that the window regions contain practically no CH₄ or Ar; these molecules are predominantly adsorbed within the cages. CO₂and N₂ molecules adsorb both within the cages and at the window regions. Due to segregated adsorption, the ideal adsorbed solution theory is unable to predict the mixture loadings accurately. Molecular dynamics simulations show that CO₂ molecules that are strongly adsorbed at the windows hinder the inter-cage diffusion of partner molecules in mixtures; this effect is not described by the Maxwell-Stefan theory.