ZK‐5: A CO₂‐Selective Zeolite with High Working Capacity at Ambient Temperature and Pressure

Abstract

Abstract 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 CO 2 . Herein, an 8‐membered‐ring zeolite ZK‐5 (Framework Type Code: KFI) exchanged with different cations (H + , Li + , Na + , K + , Mg 2+ , Ca 2+ ) was synthesized as novel CO 2 adsorbent. The samples were characterized by SEM, energy‐dispersive X‐ray spectroscopy (EDAX), XRD, and gas adsorption (CO 2 and N 2 ). The Toth adsorption model was used to describe the CO 2 adsorption isotherms, and the isosteric heats of adsorption were calculated. CO 2 capture adsorbent evaluation criteria such as working capacity, regenerability and CO 2 /N 2 selectivity were applied to evaluate the zeolite adsorbents for PSA/VSA applications. The in situ FTIR CO 2 adsorption spectra show that physisorption accounts for the largest fraction of the total CO 2 adsorbed. The CO 2 adsorption analysis shows that Mg‐ZK‐5 is the most promising adsorbent for PSA applications with the highest working capacity (Δ N =2.05 mmol g −1 ), excellent selectivity ( α =121), and low isosteric heat. Li‐, Na‐ and K‐ZK‐5 with good working capacity (Δ N =1.55–2.16 mmol g −1 ) and excellent selectivity ( α =103–128) are promising CO 2 adsorbents for the VSA working region.