Purification of Hydrogen from CO with Cu/ZSM-5 Adsorbents.

The transition to a hydrogen economy requires the development of cost-effective methods for purifying hydrogen from CO. In this study, we explore the possibilities of Cu/ZSM-5 as an adsorbent for this purpose. Samples obtained by cation exchange from aqueous solution (AE) and solid-state exchange with CuCl (SE) were characterized by in situ EPR and FTIR, H-TPR, CO-TPD, etc. The AE samples possess mainly isolated Cu cations not adsorbing CO. Reduction generates Cu sites demonstrating different affinity to CO, with the strongest centres desorbing CO at about 350 °C. The SE samples have about twice higher Cu/Al ratios, as one H is exchanged with one Cu cation. Although some of the introduced Cu sites are oxidized to Cu upon contact with air, they easily recover their original oxidation state after thermal treatment in vacuum or under inert gas stream. In addition, these Cu centres regenerate at relatively low temperatures. It is important that water does not block the CO adsorption sites because of the formation of Cu(CO)(HO) complexes. Dynamic adsorption studies show that Cu/ZSM-5 selectively adsorbs CO in the presence of hydrogen. The results indicate that the SE samples are very perspective materials for purification of H from CO.