Selective Adsorption of CO2on Zeolites NaK-ZK-4 with Si/Al of 1.8-2.8
Artikel i vetenskaplig tidskrift, 2020

Zeolites with appropriately narrow pore apertures can kinetically enhance the selective adsorption of CO2 over N2. Here, we showed that the exchangeable cations (e.g., Na+ or K+) on zeolite ZK-4 play an important role in the CO2 selectivity. Zeolites NaK ZK-4 with Si/Al = 1.8-2.8 had very high CO2 selectivity when an intermediate number of the exchangeable cations were K+ (the rest being Na+). Zeolites NaK ZK-4 with Si/Al = 1.8 had high CO2 uptake capacity and very high CO2-over-N2 selectivity (1190). Zeolite NaK ZK-4 with Si/Al = 2.3 and 2.8 also had enhanced CO2 selectivity with an intermediate number of K+ cations. The high CO2 selectivity was related to the K+ cation in the 8-rings of the α-cage, together with Na+ cations in the 6-ring, obstructing the diffusion of N2 throughout the zeolite. The positions of the K+ cation in the 8-ring moved slightly (max 0.2 Å) toward the center of the α-cage upon the adsorption of CO2, as revealed by in situ X-ray diffraction. The CO2-over-N2 selectivity was somewhat reduced when the number of K+ cations approached 100%. This was possibly due to the shift in the K+ cation positions in the 8-ring when the number of Na+ was going toward 0%, allowing N2 diffusion through the 8-ring. According to in situ infrared spectroscopy, the amount of chemisorbed CO2 was reduced on zeolite ZK-4s with increasing Si/Al ratio. In the context of potential applications, a kinetically enhanced selection of CO2 could be relevant for applications in carbon capture and bio- and natural gas upgrading.

Författare

O. Cheung

Uppsala universitet

Arrhenius Laboratory

Zoltán Bacsik

Arrhenius Laboratory

Nicolas Fil

Arrhenius Laboratory

Panagiotis Krokidas

Arrhenius Laboratory

Demokritos National Centre for Scientific Research

Dariusz Wojciech Wardecki

Uniwersytet Warszawski

Chalmers, Kemi och kemiteknik, Energi och material, Oorganisk miljökemi 2

Arrhenius Laboratory

Niklas Hedin

Arrhenius Laboratory

ACS Omega

24701343 (eISSN)

Vol. 5 39 25371-25380

Ämneskategorier

Materialkemi

Annan kemiteknik

Organisk kemi

DOI

10.1021/acsomega.0c03749

PubMed

33043217

Mer information

Senast uppdaterat

2020-11-13