Diffusion in Carbon Molecular Sieves

Abstract

Kinetic data are reported for sorption of O₂, N₂, Ar, CH₄ and CO₂ in Bergbau-Forschung carbon molecular sieve. It is shown that for O₂, N₂ and Ar the data are consistent with internal diffusion control whereas the data for CH₄ are consistent with surface resistance control. CO₂ shows a transition from surface rate control at lower temperatures to diffusion control at higher temperatures. The data (particularly for CO₂) are consistent with a dual resistance model. The relative importance of the two resistances depends on the ratio of their time constants which is affected by changes in temperatures or pressure as well as by subtle differences in sample pre-treatment.