Prediction of Binary Gas Diffusion in Carbon Molecular Sieves at High Pressure

Abstract

A dual-resistance model, in which a barrier resistance confined at the micropore mouth is assumed to act in series with pore diffusional resistance distributed in the micropore interior, has been proposed for multicomponent transport of gases in carbon molecular sieves (CMS). Excellent predictive power of the model has been thoroughly validated by means of extensive unary/binary integral uptake and breakthrough measurements involving large pressure steps on Takeda and Bergbau Forschung (BF) CMS samples. Quantitative agreement between the experimental and predicted results is truly remarkable considering the fact that all the predictions are strictly based on independently measured single-component equilibrium and kinetic parameters. Impact of two mixture isotherms, namely ideal adsorbed solution (IAS) theory and extended Langmuir (E-L) model, on mixture uptakes has also been investigated. This study undeniably establishes the following: (1) effectiveness of a dual-resistance approach for gas transport in CMS micropores, and (2) much stronger concentration dependence of the transport parameters than that predicted from the use of a chemical potential gradient as the driving force for diffusion with constant intrinsic mobility. © 2004 American Institute of Chemical Engineers.