期刊
AICHE JOURNAL
卷 69, 期 8, 页码 -出版社
WILEY
DOI: 10.1002/aic.18139
关键词
direct air capture of CO2 (DAC); metal cations; physisorbents; zeolite LTA
Direct air capture of CO2 (DAC) is a promising carbon-negative technology, and the key lies in effective sorbent materials. The research found that a large charge-to-size ratio of cations is critical to the high DAC capacity of LTA zeolites, while an excessively large ratio has a detrimental effect. Ca-LTA with an appropriate ratio exhibited the highest DAC capacity with fast kinetics and good reusability. These results provide valuable insights for the design of zeolite-based physisorbents for DAC.
Direct air capture of CO2 (DAC) has been increasingly recognized as a promising carbon-negative technology. The challenge in deploying energy-efficient DAC lies in effective sorbent materials. In this research, we comprehensively investigated the DAC behavior of LTA zeolites exchanged with different metal cations (Na+, K+, Mg2+, Ca2+, Mn2+, Co2+, Ni2+, Cu2+, Zn2+, Y3+, La3+, Ce3+, Eu3+, Tb3+, and Yb3+) by both static single-component gas adsorption and dynamic mixture gas adsorptive separation tests. We found that a large charge-to-size ratio of cations is critical to imparting a high DAC capacity of LTA zeolites, which is ascribed to the enhanced electrostatic interaction and/or p-back bonding toward CO2. Meanwhile, a detrimental effect is associated with an excessively large charge-to-size ratio, that is, a significant shielding effect of (pre-) adsorbed contaminants (e.g., H2O and CO2) on cations (e.g., Mn2+ and Mg2+) reduce the accessible CO2 capacity. Ca-LTA featuring Ca2+ with an appropriate charge-to-size ratio exhibits the highest DAC capacity (350 ppm CO2 in the air, 1.20 mmol/g) with fast kinetics and good reusability. These results provide valuable insights for the design of zeolites-based physisorbents for DAC.
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