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Carbon Dioxide Capture and Separation with Membranes or Sorbents Based on Selective Porous Materials
Abstract
Global warming has been one of the human beings' main concerns. It’s urgent and desired to realize carbon capture and storage (CCS), as an important portion of the sustainability blueprint. Mixed matrix membranes (MMMs) are considered as competitive materials in the treatment of post-combustion flue gas, especially for the CO2/N2 separation. However, one challenge of MMMs is the poor compatibility between the inorganic fillers and the organic matrix, which leads to nonselective pores or pore blockage.
Herein, I proposed a method of utilizing soluble CO2 selective metal-organic polyhedra (MOPs) as the fillers to fabricate MMMs for CO2/N2 separation. The solubility of MOPs endows them the potential to be molecularly dispersed into the MMM and thus achieve products of homogeneous MMMs. One kind of CO2 selective MOP, UMC-1, was selected as the filler and one commercially available polymer, poly(ethylene glycol) diacrylate (PEGDA), was chosen as the matrix. Several technical processes were taken to obtain UMC-1@cross-linked PEGDA (XLPEGDA) MMMs with flexibility, uniformity and controlled loading ratio and thickness. The addition of MOPs improved the gas separation performance and only a small portion of filler is needed. To be detailed, UMC-1@XLPEGDA membrane with only 3 wt% of UMC-1 exhibited a permeability of CO2 at 64.0 Barrer and selectivity of CO2/N2 at 112.6, which exceeds the Robeson upper bound.
Besides membrane separation, sorbent is another vital and commercially used approach in CCS. Amine-functionalized sorbents are of great interest since the affinity to CO2 increases capture ability greatly, especially under low concentrations. I used porous polymer networks (PPNs) that surface was modified by amine groups as sorbents and fabricate them into hollow fibers to achieve continuous adsorption and desorption processes. Several kinds of PPNs were selected as potential candidates and exhibited very promising carbon capture performance, like up to 5 wt% adsorption ability under dry conditions and 18 wt% under humid conditions. Now it has been scaled up for hollow fiber spinning with high potential remaining high capture ability due to the good compatibility with hollow fiber matrix.
Citation
Chen, Fan (2023). Carbon Dioxide Capture and Separation with Membranes or Sorbents Based on Selective Porous Materials. Doctoral dissertation, Texas A&M University. Available electronically from https : / /hdl .handle .net /1969 .1 /199181.