ASSESSMENT OF THE EFFECT OF IMPURITY GASES ON THE STORAGE CAPACITY OF HYDROGEN ON ACTIVATED CARBON USING THE CONCEPT OF EFFECTIVE ADSORBED PHASE MOLAR VOLUME

Hydrogen storage on activated carbon appears to be a viable method for either mobile or stationary applications. Impurity gases in the H-2 delivery system can affect the storage capacity of the activated carbon. Thus, reliable procedures must be developed to assess the extent of such decreases in storage capacity. The Ideal Adsorbed Solution (IAS) model, the Grant and Manes model and the model by Doong and Yang were applied to high pressure adsorption data for a dilute N2 in H-2 mixture on an activated carbon. These theories, though applicable to a wide number of binary systems, failed to predict total adsorbed amounts of the hydrogen/nitrogen system at a relatively low concentration of nitrogen. The concept of effective adsorbed phase molar volume, which empirically takes into account inter-species interaction and the effect of affinity coefficients is introduced. This concept is incorporated into a model for predicting binary gas adsorption on the basis of adsorption data for the pure components. The results are found to work well for this system. It is shown that, using superactivated carbon as the adsorbent, the reduction in adsorbed amounts of hydrogen due to the presence of amounts of nitrogen in the 500 ppm range will not exceed 30%.