Surface effects and CO/CO2 influence in the H2 permeation through a Pd-Ag membrane: A comprehensive model

The permeability of a 0.175 mm thick Pd-Ag tubular membrane to pure H2 and binary mixtures of H2/CO or H2/CO2 was studied. The tests were performed in a wide range of temperature (523-723 K) and pressure (200-800 kPa). Pure H2-permeation through a dense metal membrane is described by the Sieverts' law. However, it was already found that the H2 permeation does not follow the Sieverts' law when other components are present in the feed and namely CO or CO2. In this work, it is proposed a new permeation model based on the Sieverts' law considering: i) the mass transfer resistance due to the surface effects and ii) the barrier effect due to the presence of either CO or CO2. The model was successfully validated against experimental data of hydrogen permeation for binary (H2/CO and H2/CO2) experiments for every working temperature and pressure. Copyright © 2015, Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights reserved.