Abstract
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, H2-TPR, CO-TPD, etc. The AE samples possess mainly isolated Cu2+ 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 Cu2+ 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)(H2O)x 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 H2 from CO.
Highlights
One of the strategic priorities of the future is the transition to a hydrogen economy
The conditions of solid-state exchange suggest the removal of excess CuCl, the data from the analysis show a certain content of chlorine in the samples
Cu/ZSM-5 zeolites obtained by solid-state exchange using CuCl are perspective materials for the purification of H2 from CO
Summary
One of the strategic priorities of the future is the transition to a hydrogen economy. Hydrogen is considered the main fuel of the future, with a wide range of applications: stationary and mobile. Significant difficulties in some practical applications of hydrogen are related to its purification and storage. The purity of hydrogen is an essential requirement for its effective sorption and for its subsequent use. In order to prevent catalyst poisoning in fuel cells, it is necessary that the CO content in hydrogen does not exceed 10 ppm [3,4]. Hydrogen purification is an important technological step before its storage. Pressure swing adsorption (PSA) is used to effectively purify H2 from CO2 [5–9], and catalytic oxidation is used to remove oxygen impurities [10]. In order to purify from CO, catalysts for the preferential oxidation of CO in the presence of H2 have been developed [11,12]. Membranes are often used to remove various gas impurities, while metal hydrides are effective in separating H2 from inert components [4,6,13]
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