ZK-5: a CO₂-selective zeolite with high working capacity at ambient temperature and pressure.
The increased carbon dioxide concentration in the atmosphere caused by combustion of fossil fuels has been a leading contributor to global climate change. The adsorption-driven pressure or vacuum swing (PSA/VSA) processes are promising as affordable means for the capture and separation of CO₂. Herein, an 8-membered-ring zeolite ZK-5 (Framework Type Code: KFI) exchanged with different cations (H⁺, Li⁺, Na⁺, K⁺, Mg²⁺, Ca²⁺) was synthesized as novel CO₂ adsorbent. The samples were characterized by SEM, energy-dispersive X-ray spectroscopy (EDAX), XRD, and gas adsorption (CO₂ and N₂). The Toth adsorption model was used to describe the CO₂ adsorption isotherms, and the isosteric heats of adsorption were calculated. CO₂ capture adsorbent evaluation criteria such as working capacity, regenerability and CO₂/N₂ selectivity were applied to evaluate the zeolite adsorbents for PSA/VSA applications. The in situ FTIR CO₂ adsorption spectra show that physisorption accounts for the largest fraction of the total CO₂ adsorbed. The CO₂ adsorption analysis shows that Mg-ZK-5 is the most promising adsorbent for PSA applications with the highest working capacity (ΔN(CO₂)=2.05 mmol g⁻¹), excellent selectivity (α(CO₂/N₂)=121), and low isosteric heat. Li-, Na- and K-ZK-5 with good working capacity (ΔN(CO₂)=1.55-2.16 mmol g⁻¹) and excellent selectivity (α(CO₂/N₂)=103-128) are promising CO₂ adsorbents for the VSA working region.
Department of Chemical and Biomolecular Engineering, Center for Catalytic Science and Technology, University of Delaware, 150 Academy St., Newark, DE 19716, USA.
Qingling
Q
Liu
Trong
T
Pham
Marc D
MD
Porosoff
Raul F
RF
Lobo
D000327:Adsorption; D002245:Carbon Dioxide / Q000737:chemistry*; D008958:Models, Molecular; D008968:Molecular Conformation; D009584:Nitrogen / Q000737:chemistry; D011312:Pressure; D017550:Spectroscopy, Fourier Transform Infrared; D013696:Temperature; D014618:Vacuum; D017641:Zeolites / Q000737:chemistry*
D017641:Zeolites; D002245:Carbon Dioxide; D009584:Nitrogen