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Adsorption and Separation of CO2 on KFI Zeolites: Effect of Cation Type and Si/Al Ratio on Equilibrium and Kinetic Properties

Remy, Tom, Peter, Sunil A., Van Tendeloo, Leen, Van der Perre, Stijn, Lorgouilloux, Yannick, Kirschhock, Christine E. A., Baron, Gino V., Denayer, Joeri F. M.
Langmuir 2013 v.29 no.16 pp. 4998-5012
adsorption, aluminum, calcium, carbon dioxide, cations, chemical industry, lithium, magnesium, methane, nitrogen, silicon, sodium, strontium, zeolites
Selective separation of CO₂ is becoming one of the key technologies in the (petro-) chemical industry. This study focuses on the adsorption and separation of CO₂ from CH₄ on a new low-silica (LS) type of the eight-membered ring KFI zeolite. A series of alkali (Li, Na, K) and alkaline-earth (Mg, Ca, Sr) exchanged samples of the new LS KFI were synthesized and characterized. LS Li-KFI showed the largest pore volume, whereas LS Na-KFI and LS K-KFI were inaccessible for Argon at 87 K. Adsorption of CO₂ at 303 K demonstrated the dominant quadrupolar interaction on alkali-exchanged LS KFI samples. LS Li-KFI showed the largest capacities upon high pressure isotherm measurements of CO₂ (4.8 mmol/g), CH₄ (2.6 mmol/g), and N₂ (2.2 mmol/g) up to 40 bar at 303 K. The performance of the new LS KFI was compared to a KFI sample (ZK-5) with a higher Si/Al ratio. Isotherm measurements and dynamic breakthrough experiments demonstrated that ZK-5 samples show larger working capacities for CO₂/CH₄ separations at low pressure. Li-ZK-5 and Na-ZK-5 show the highest capacities and high selectivities (similar to benchmark 13X).