Highly Polar Polymers with Superior Membrane CO2/N2 Separation Properties for Carbon Capture

Greenhouse gas CO2 emissions to the atmosphere are believed to be the primary reason for the global warming. One effective way to mitigate CO2 emissions is to capture CO2 from post-combustion flue gas in coal-fired power plants. Membrane technology has been widely explored for this application due to its high energy-efficiency. Current membrane materials are often based on poly(ethylene oxide) (PEO) because the ether oxygens in PEO interact favorably with CO2, leading to high CO2 solubility, and thus high CO2/N2 selectivity. In this study, we demonstrate that polymers with higher ether oxygen content than PEO exhibit enhanced CO2/N2 separation performance. Specifically, a family of polymers containing poly(1,3dioxolane) (with an O:C ratio of 2:3, compared to 1:2 in PEO) were synthesized by photopolymerization of two macromonomers, poly(1,3-dioxolane) acrylate (PDXLA) and poly(1,3-dioxolane) ethyl ether acrylate (PDXLEA). The macromonomers and polymers were systematically characterized for chemical structures and physical properties using NMR, DSC, FTIR, XRD, etc. Pure-gas solubility and pure‐ and mixed-gas permeability were determined as a function of pressures and temperatures. These highly polar polymers exhibit CO2/N2 separation properties above the upper bound in the Robeson’ plot. For example, a copolymer prepared from PDXLA and PDXLEA (1:1) exhibits a CO2 permeability of 840 Barrers with a CO2/N2 selectivity of 54 at 35oC, which are the best among those reported in the literature. The relationship between polymer structure and gas transport properties will also be discussed in this presentation.