Facilitated transport membrane with fixed and mobile carriers is essential yet challenging to improve the CO 2 capture. Herein, a facilitated transport membrane with continuous pathway was constructed by the in-situ interlinkage of mobile aniline with the fixed carriers distributing along electrospun polyacrylonitrile (PAN) nanofibers. In this membrane, fixed amine carriers are introduced through the alkalinous hydrolysis of PAN fibers (HPAN), and are distributed along the HPAN fibers to construct a long-range continuous transport pathway for CO 2 . The mobile aniline carriers are introduced into the interfibrous voids of the HPAN nanofibers mat (NFM) by in-situ polymerization of Poly (ethylene glycol) diacrylate (PEGDA), which interlink the fixed amine carriers to achieve the facilitated transport pathway continuous completely. And the fixed amine and mobile aniline carriers are demonstrated to co-exist in the An/PEO@HPAN membrane (NFCM) by the FTIR and XPS results. Meanwhile, the XRD and DSC results indicate that the introduction of aniline increases the free volume of PEO matrix, which is beneficial for enhancing CO 2 permeation. Therefore, the 10 wt% An/PEO@HPAN-3h NFCM presents 90.81 % and 13.15 % increases in CO 2 permeability and CO 2 /N 2 selectivity under mixed gas at 0.3 MPa in contrast with the membrane without mobile aniline carriers. Under mixed gas conditions, this NFCM exhibits CO 2 permeability of 202.93 Barrer and CO 2 /N 2 selectivity of 83.89 at 0.1 MPa, reaching the 2019 McKeown upper bound.
Amine-rich facilitated transport membranes (FTMs) attract great interest in intensifying the membrane-based CO 2 separation processes. The high-molecular-weight polyvinylamine (PVAm) polymers containing fixed-site carriers of the amino groups were used to prepare highly CO 2 -permeable membranes. The sterically hindered PVAm polymers of poly(N-methyl-N-vinylamine) and poly(N-isopropyl-N-vinylamine) were obtained by functionalization of PVAm to provide superior CO 2 solubility. By loading the mobile carriers of amino acid salt (AAS) and CO 2 -philic graphene oxide (GO), the prepared FTMs render enhanced CO 2 permeance and CO 2 /N 2 selectivity. The d-spacing of 8.8 Å and the ultramicropores of 3.5 Å from GO nanosheets provide the combination of both selective surface flow and molecular sieving mechanisms to achieve improved CO 2 permeance and CO 2 /N 2 selectivity. In addition, the intercalation of GO hinders N 2 transport through the membrane due to a longer pathway, while the mobile carriers of AAS introduced into the PVAm matrix facilitate CO 2 transport through the selective layer. Therefore, the CO 2 /N 2 selectivity of the prepared FTMs was significantly enhanced to 171 based on the intensified carrier-driving transport mechanism. It can be concluded that amine-rich membranes based on both fixed and mobile carriers of the amino groups together with intercalated GO can synergistically improve the CO 2 /N 2 separation performance, and be potentially applied for CO 2 capture from flue gas .
Lixinyu Wang,Yidan Zhou,Shangwen Zha,Shenxiang Zhang,Jian Jin
Membrane-based postcombustion carbon capture is a promising method for reducing carbon dioxide (CO2) emissions. Mobile carrier-facilitated transport membranes (FTMs) are receiving attention because they can simultaneously increase CO2 permeability and CO2/N2 selectivity. However, FTMs still face the challenge of carrier loss. Stable immobilization of mobile carriers is essential for achieving and maintaining superior separation performance of FTMs. Herein, we report an ionic covalent organic framework (COF) membrane with confined mobile carriers for stable and efficient CO2 separation. In this structure, a typical CO2 mobile carrier, 2,5-diethylenetriamine (DETA), is stabilized in the negatively charged nanochannels of the COF membrane. Thanks to the intrinsic CO2-facilitated transport of DETA, the COF membrane presents a CO2 permeance of 2347 GPU and a CO2/N2 selectivity of 191 under simulated flue gas conditions. Because the CO2 mobile carriers are firmly confined within the pores through electrostatic interactions, the membrane shows stable separation performance during the 310 h continuous test. The excellent performance and robust stability demonstrate the significant potential of this innovative membrane structure for practical use in the capture of CO2 from flue gas.
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