Investigating the effect of water vapor on CO2/CH4 separations in primary- and hindered-amine-functional microporous polymers
Name
2025_PAD_humidified manuscript.pdf
Description
Accepted version
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744.45 KB
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Name
2025_PAD_humidified manuscript SI.pdf
Description
Supporting information
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638.8 KB
Format
Adobe PDF
Checksum (MD5)
4a2ed3d6061ab5df8262f566076426ce
Author(s)
Dean, Pablo A
Gleason, Kristofer L
Smith, Zachary P
Date Issued
September 2025
Journal
Journal of Membrane Science
Publisher
Elsevier BV
Version
Author's final manuscript
Abstract
“Competitive sorption” between CO2 and co-permeating lighter gases can be leveraged in amine-functional materials, such as PIM-NH2, to improve CO2-based mixed-gas selectivity relative to pure-gas selectivity. In this work, competitive sorption effects were investigated for amine-functional microporous polymers in the presence of water vapor, an understudied yet common impurity in natural gas and biogas. Mixed-gas CO2 transport is reported for dry and humid conditions for PIM-NH2 and a PIM-1 control. Additionally, a novel hindered-amine-functional analog, PIM-NHiPr, was synthesized and tested for comparison. Multi-temperature permeation experiments were conducted to recover dry and humidified permeation energetics, and water vapor and single-gas sorption isotherms were collected to evaluate fundamental transport behavior. Our results show that the activation energies of permeation for CO2 in PIM-NH2 and PIM-NHiPr significantly increase (by over 2-fold) in humid conditions relative to the dry case, while the activation energy in PIM-1 shows no significant change, highlighting the strong effect of water vapor on gas transport in membranes with hydrophilic functional groups. Additionally, single-to-mixed-gas CO2/CH4 selectivity improvements in PIM-NH2 (more than 8-fold) and PIM-NHiPr (more than 3-fold) are maintained in both dry and humid conditions, indicating strong CO2–amine interactions despite the presence of water vapor. This study provides a systematic analysis of dry and humidified CO2-based transport in amine-functional polymer films, with fundamental insights regarding permeation energetics and sorption to connect separation performance to sorption–diffusion-based transport theory.
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Creative Commons Attribution-NonCommercial-NoDerivatives
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DOI of Published Version
https://doi.org/10.1016/j.memsci.2025.124336
