(211c) Modeling Gas Permeation in Nanopores

An analytical theory for permeation in a pressure gradient is described and applied to the separation of a gas mixture in a nanopore. The theory is based on the solution of a novel transport equation for the probability distribution used to calculate non-equilibrium system properties. The interactions between gas molecules and with the tube walls modify simple diffusive transport in the mean field approximation of density functional theory and cause large variations in the adsorption and the permeance with applied pressure[1]. The density and average velocity profiles of the molecules can be followed as a function of position within the pore. Large separation occurs in particular in a tube of radius close to the molecular size. Similar to equilibrium capillary condensation[2], nonlocal contributions in an expansion in the density gradient cause the tube to fill when one of the components nears condensation. [1] A. ten Bosch, Separation and Purification Technology 47 (2006)156 [2] F. Celestini, Phys. Lett. A 228 (1997)84