On the Structure-Property Relationships of Cation-Exchanged ZK-5 Zeolites for CO ₂ Adsorption

Journal Article · Thu Feb 16 00:00:00 EST 2017 · ChemSusChem

DOI:https://doi.org/10.1002/cssc.201601648· OSTI ID:1347013

Pham, Trong D. ^[1]; Hudson, Matthew R. ^[2]; Brown, Craig M. ^[3]; Lobo, Raul F. ^[1]

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1. Department of Chemical and Biomolecular Engineering, University of Delaware, Newark Delaware 19716 USA
2. Center for Neutron Research, National Institute of Standards and Technology, Gaithersburg Maryland 20899 USA
3. Department of Chemical and Biomolecular Engineering, University of Delaware, Newark Delaware 19716 USA; Center for Neutron Research, National Institute of Standards and Technology, Gaithersburg Maryland 20899 USA

The CO₂ adsorption properties of cation-exchanged Li-, Na-, K-, and Mg-ZK-5 zeolites were correlated to the molecular structures determined by Rietveld refinements of synchrotron powder X-ray diffraction patterns. Li-, K-, and Na-ZK-5 all exhibited high isosteric heats of adsorption (Qst) at low CO₂ coverage, with Na-ZK-5 having the highest Qst (ca. 49 kJ mol^-1). Mg2+ was located at the center of the zeolite hexagonal prism with the cation inaccessible to CO₂, leading to a much lower Qst (ca. 30 kJ mol-1) and lower overall uptake capacity. Multiple CO₂ adsorption sites were identified at a given CO₂ loading amount for all four cation-exchanged ZK-5 adsorbents. Site A at the flat eight-membered ring windows and site B/B* in the γ-cages were the primary adsorption sites in Li^- and Na-ZK-5 zeolites. Relatively strong dual-cation adsorption sites contributed significantly to an enhanced electrostatic interaction for CO₂ in all ZK-5 samples. This interaction gives rise to a migration of Li⁺ and Mg²⁺ cations from their original locations at the center of the hexagonal prisms toward the α-cages, in which they interact more strongly with the adsorbed CO₂.

• Research Organization: Argonne National Lab. (ANL), Argonne, IL (United States). Advanced Photon Source (APS)
• Sponsoring Organization: USDOE Office of Science (SC), Basic Energy Sciences (BES)
• OSTI ID: 1347013
• Journal Information: ChemSusChem, Vol. 10, Issue 5; ISSN 1864-5631
• Publisher: ChemPubSoc Europe
• Country of Publication: United States
• Language: ENGLISH

Related Subjects

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY