This study investigated the permeation behaviors of n-hexane and 2-methylpentane through two-types of silicalite-1 membranes that have different pore-connectivity. The permeation mechanisms of these hydrocarbons were able to be explained by the adsorption-diffusion model. In addition, the fluxes through silicalite-1 membranes could be expressed by the modified Fick's first law. The hydrocarbon fluxes through S-1S with better pore-connectivity were ca. 3-20 times larger than those through S-1M with poor pore-connectivity. For these membranes with different pore-connectivity, the activation energy of diffusion of n-hexane was 17.5 kJ mol-1 for the membrane with better pore-connectivity and 18.0 kJ mol-1 for the membrane with poorer pore-connectivity, whereas for 2-methylpentane it was 17.9 and 33.0 kJ mol-1, respectively. We concluded that the pore-connectivity in silicalite-1 membrane significantly influences the molecular diffusivities.
Keywords: adsorption; connectivity; diffusion; membrane; micropore; separation; silicalite-1.