Metal cation-exchanged LTA zeolites for CO2/N2 and CO2/CH4 separation : The roles of gas-framework and gas-cation interactions

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Author(s)

  • Aamir Hanif
  • Vienna Chan
  • Qinfen Gu

Detail(s)

Original languageEnglish
Article number100126
Journal / PublicationCarbon Capture Science and Technology
Volume8
Online published18 Jun 2023
Publication statusPublished - Sept 2023

Link(s)

Abstract

Selective CO2 adsorption for efficient carbon capture from flue gas (CO2/N2 - 15/85, v/v) and biogas (CO2/CH4 - 50/50, v/v) is important for achieving global energy and climate goals but remains a challenge due to the lack of effective adsorbents. To address this issue, we attempted to develop zeolite adsorbents by systematically investigating the effect of different extra-framework metal cations (i.e., Na+, Ca2+, Mn2+, and Ce3+-exchanged in LTA zeolites) on selective CO2 adsorption from CO2/N2 and CO2/CH4. Analyzing the isosteric heat of adsorption results showed that CO2 adsorption at moderate pressure (e.g., 15 and 50 kPa relevant to the compositions of flue gas and biogas, respectively) is governed by the gas-framework interaction. On the other hand, the adsorption of N2 and CH4 was found to be dominated by the gas-cation interaction. Therefore, we concluded that metal cations with a small charge-to-size ratio are beneficial for selective CO2 adsorption from flue gas and biogas because they tend to induce strong CO2-framework interaction (due to the enhanced charge induction to zeolite framework O) and weak N2 or CH4-cation interaction (due to the weakened gas-cation electrostatic interaction). Specifically, LTA zeolites in the form of Na+, with the smallest charge-to-size ratio of cation in this study, exhibit the highest CO2 uptake and separation factor of CO2/N2 and CO2/CH4, as demonstrated by both static single-component adsorption and dynamic binary adsorption results. In addition, the potential of metal cation-exchanged LTA zeolites for VSA and PSA processes was evaluated. Our study provides valuable insights for designing small-pore zeolites as adsorbents for carbon capture. © 2023 The Authors. Published by Elsevier Ltd on behalf of Institution of Chemical Engineers (IChemE).

Research Area(s)

  • Biogas, Carbon capture, Flue gas, Gas framework interaction, Gas-cation interaction, Metal cation-exchanged LTA zeolites

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