Capillary condensation and adsorption of binary mixtures

31 pagesThe adsorption of equimolar binary mixtures of hydrogen-carbon dioxide, hydrogen-methane and methane-carbon dioxide in porous material models is determined by Grand Canonical Monte Carlo simulations. The material models have an adsorbent surface similar to that of nanofibers with a herringbone structure. Our main result, which is relevant for hydrogen purification and carbon dioxide capture, is that the adsorption selectivities calculated for the mixtures can differ significantly from those deduced from simulations of the adsorption of pure gases, in particular when one of the adsorbed gases presents a capillary condensation induced by confinement within the pore network. A comparison of our data is also made with theoretical models used in the literature for predicting the properties of the mixture adsorption

Impact of the carbonisation temperature on the activation of carbon fibres and their application for hydrogen storage

Special issue: 2nd World Congress of Young Scientists on Hydrogen Energy Systems.Porous materials are gaining interest due to their potential for storing hydrogen via physisorption. In the present work, two carbon fibres, carbonised at 973 and 1273 K, have been chemically activated with KOH and NaOH, in order to obtain materials with optimised characteristics for hydrogen storage application. Highly microporous activated carbon fibres were obtained from both precursors, especially from the fibre carbonised at the lower carbonisation temperature, remarking its importance on its subsequent activation process. As activation agent, KOH is more effective for developing the narrow microporosity, and higher yields are obtained. H2 adsorption isotherms were measured at 298 K for pressures up to 20 MPa, and at 77 K up to 4 MPa. The maximum excess adsorption of hydrogen reached 1 wt% at 298 K and 3.8 wt% at 77 K. The total volumetric storage capacity is of 17 g/l at 298 K, and 32 g/l at 77 K.Financial help from the European Union (Marie Curie Research Training Network—HyTRAIN Project reference:512443), MEC (Accion complementaria; ENE2005-23824-E/CON), the Generalitat Valenciana (Accion complementaria; ACOMP06/089) and MEC-CTQ2006-08958PPQ. Samples supplied by Osaka gas Co., Ltd

Herringbone nanofiber CVD synthesis and high pressure hydrogen adsorption performance analysis by molecular modelling

In order to interpret adsorption results of hydrogen storage by adsorption in graphite nanofiber (GNF) materials at molecular scale and to propose optimized structures of graphitic materials, we have realized both experimental and numerical studies of gas adsorption in GNF. The porous materials have been synthesized by CVD method. The adsorption experiments were performed at 293 K by a volumetric method at high pressure until 40 MPa. We completed the surface reactivity analysis by performing structural characterizations of the samples using different structural techniques and numerical modelling computed in the grand canonical Gibbs ensemble. Within the cell, stacks of plans of graphite are arranged periodically using boundary conditions. The present numerical approach enables to interpret the results based on the solid-gas molecular interactions reactivity analysis. (c) 2008 International Association for Hydrogen Energy. Published by Elsevier Ltd. All rights reserved