Direct air capture of CO2 by metal cation-exchanged LTA zeolites : Effect of the charge-to-size ratio of cations

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Detail(s)

Original languageEnglish
Article numbere18139
Journal / PublicationAIChE Journal
Volume69
Issue number8
Online published17 May 2023
Publication statusPublished - Aug 2023

Abstract

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 π-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. © 2023 American Institute of Chemical Engineers.

Research Area(s)

  • direct air capture of CO2 (DAC), metal cations, physisorbents, zeolite LTA, MONTE-CARLO-SIMULATION, CARBON-DIOXIDE, ORGANIC FRAMEWORK, PI-COMPLEXATION, ION-EXCHANGE, ADSORPTION, CH4, SEPARATION, N-2, WATER