Characterization of Amine-Functionalized Facilitated Transport Membranes for CO2 Separation
Amine functional groups in polymeric facilitated transport membranes (FTMs) selectively and reversibly facilitate the transport of CO2 over other gases, which results in rapid and selective CO2 separation from mixed gas streams, such as CO2/N2. However, the mechanisms of CO2 transport by amine functional groups across membranes are not well understood. Water vapor is known to enhance CO2 permeation rates through amine-functionalized polymeric membranes; however, it is unclear how exactly water influences the CO2 transport. To address the fundamental issues of CO2 facilitated transport, we have developed a novel operando transmission FTIR spectroscopic permeation tool to directly observe the formation of CO2 transport intermediates through amine-based FTMs under realistic operating conditions, including dry and humid CO2 gas mixtures, and simultaneously correlate the formation of these intermediate species with the CO2 permeation rates through the same sample. This work describes the development of this novel operando transmission FTIR spectroscopic tool, and first demonstrates its utility by probing the mechanism of water-enhanced CO2 transport through polyvinylamine (PVAm), a model primary amine that it a typical FTM used for CO2 separations. We show that water enhances CO2 permeation across PVAm by facilitating the conversion of CO2 to a reactive intermediate, which is most consistent with an ammonium carbamate species based on the infrared band positions. To further probe the fundamental issues of CO2 permeation, we will study the effect of water-enhanced CO2 permeation on poly(N-methyl-N-vinylamine) (PMVAm), poly(N,N-dimethyl-N-vinylamine) (PDVAm), polyvinylpyridine, and quaternized polyvinylpyridine materials to investigate the effect of amine structure on CO2 transport through membranes. Next, we will further investigate how the presence or absence of water influences CO2 transport through these same materials through exposure to dry CO2/N2 and humid N2. These investigations allow us to clarify the effect of amine structure and the role of water for CO2 transport through amine-functionalized membranes, which ultimately allows us to propose new CO2 transport mechanisms based on the direct observation of intermediate species. This work establishes a novel operando spectroscopy tool that can be used to further study a wide range of membrane systems to probe transport mechanisms, fouling mechanisms, and correlate any changes in membrane structure to its performance over time.
History
Date Modified
2023-05-03Defense Date
2023-03-24CIP Code
- 14.0701
Research Director(s)
Casey P. O`BrienCommittee Members
Jason Hicks Ruilan Guo Jennifer SchaeferDegree
- Doctor of Philosophy
Degree Level
- Doctoral Dissertation
Alternate Identifier
1378082178OCLC Number
1378082178Program Name
- Chemical and Biomolecular Engineering