DIFFUSION OF OXYGEN, NITROGEN AND THEIR MIXTURES IN CARBON MOLECULAR-SIEVE

Diffusivities of oxygen, nitrogen and their mixtures in carbon molecul ar sieve are measured under conditions used for kinetic separation of air by adsorption (elevated pressures). In binary diffusion, codiffusi on enhances fluxes for both components, whereas counterdiffusion has t he opposite effects; for both cases, the effects are significantly mor e pronounced for the fast diffusing component. The multicomponent diff usion theory developed earlier in this laboratory for surface diffusio n is reformulated for diffusion in molecular sieves. Multicomponent di ffusivities can be predicted from the following pure-component informa tion: concentration-dependent diffusivities and diffusional activation energies. Predicted binary diffusion results agree fairly with the ex perimental data for oxygen and nitrogen in carbon molecular sieve.