Crosslinkable Polyimide Mixed Matrix Membranes for Natural Gas Purification
Hillock, Alexis Maureen Wrenn
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Crosslinkable mixed matrix membranes represent an attractive technology that promises both outstanding separation properties and swelling resistance for the purification of natural gas. This approach relies upon dispersal of a CO2/CH4 size-discriminating zeolite in a crosslinkable polymer, which is resistant to CO2 swelling when crosslinked. The resulting membrane has the potential to separate CO2 from CH4 more effectively than traditional pure polymer membranes, while also providing needed membrane stability in the presence of aggressive CO2-contaminated natural gas streams. Control studies are conducted using the pure crosslinkable polymer to observe the separation properties and swelling resistance. Initial crosslinkable mixed matrix membrane experiments are then performed and result in an increase in membrane productivity, instead of the expected increase in selectivity. Traditionally, this is caused by material incompatibility at the polymer/zeolite interface, so the crosslinkable mixed matrix membranes are characterized to examine this issue. During the material characterization, a new non-ideal transport phenomenon is discovered in the zeolite phase. A model is developed to better understand the transport and predict subsequent experimental results. Once the independent materials are proven to be viable, crosslinkable mixed matrix membranes that show enhancements in both efficiency and productivity and exhibit stability in the presence of aggressive CO2 feeds are created.