Surface diffusion in microporous media

Abstract

Abstract The surface diffusion of He, Ne, H 2 , Ar, O 2 , N 2 and CO 2 through Vycor microporous glass was analyzed theoretically and experimentally in the low pressure range as a function of temperature. A statistical‐mechanical treatment was carried out in terms of partition functions to derive a general equation of surface flow. It was possible to separate the surface diffusion from the total flow using a simplified working equation. The conventional method which assumes that there is no adsorbed flow for helium should be discarded, because the fraction of surface diffusion for helium ranges from 0.133 to 0.247. It is also illustrated how to predict the permeability of a new gas for the same porous medium.