Advanced Solubility Selective Membrane Materials for CO2 Separation from Light Gases
MetadataShow full item record
Membranes offer an alternative approach for CO2 capture from coal power plants due to their high energy efficiency, small footprint, and simplicity of operation. In contrast to amine absorption technology (which is mature and dramatic improvements in efficiency are very unlikely), membrane technology has made significant improvements in CO2 removal efficiencies in the last decade. The impressive growth of membrane technology for this application is derived from novel membrane process designs and membranes with superior CO2/light gases separation properties (i.e., high CO2 permeability and CO2/light gases permeability selectivity). The ether oxygen moiety is the only functional group known that exhibits affinity towards CO2 but not other light gases (which leads to high CO2 solubility and CO2/light gases solubility selectivity), and simultaneously retains polymer chain flexibility and thus high gas diffusivity and permeability. This dissertation systematically investigated the enhancement by introducing ether oxygen functional groups and inorganic fillers to increase the gas solubility selectivity and gas permeability. Chapter 1 provides a general rationale for materials design and highlights polymers with promising CO2/N2 separation properties for CO2 capture from flue gas. Chapter 2 focuses on preparing a series of highly branched amorphous polymers containing poly(1,3-dioxolane), which has an O:C ratio of 0.67, higher than 0.5 in PEO. The length of the poly(1,3-dioxolane)-based branches are tuned to yield amorphous nature, and mobile ethoxyl chain end groups are introduced to provide high free volume and gas diffusivity. This work demonstrates that harnessing the interactions between polymers and CO2 may provide unprecedented opportunities in designing gas separation membranes with robust performance under practical conditions. In chapter 3 we designed novel polymer materials to further increase the ratio of ether/ester oxygen to carbon as high as 0.8 using 1,3-dioxolane and 1,3,5-trioxane. These polar groups are incorporated in short branches to yield amorphous and rubbery nature, leading to high gas permeability that is stable over time. A polymer with the O:C ratio of 0.71 (P71) shows mixed-gas CO2/CH4 separation properties independent of the hexane content in the simulated natural gas at 50 oC. Chapter 4 presents the mixed matrix materials for CO2/light gases separation based on the poly(ethylene glycol) diacrylate (PEGDA) and PDXLA as the polymer matrix and copper metal organic polyhydras (MOP-3) as inorganic fillers. The MOP-3 containing mixed matrix materials achieve the superior gas separation properties and surpass the CO2/N2 and CO2/H2 upper bound. Chapter 5 is a summary and several thinkings on the ongoing project.