This technology features a polymer composed of a PI-PDMS backbone copolymer cross-linked with piperazinium, an ionic liquid-based salt, and a gas separation membrane utilizing it. A small amount of PDMS is introduced into a 6FDA-durene-based PI, and piperazinium is bonded to the brominated benzyl sites to form a side-chain cross-linked structure.
While polyimide membranes offer excellent CO2/CH4 separation performance and heat resistance, they suffer from reduced selectivity and permeability due to plasticization and aging in high-pressure or high-concentration CO2 environments. Introducing PDMS blocks significantly increases permeability, but it also leads to a sharp decline in selectivity due to increased free volume and weakens the mechanical strength of the membrane.
This technology optimizes the PI:PDMS ratio to a low PDMS composition of 350:1 to 150:1 and utilizes piperazinium, which has high CO2 affinity, as a cross-linking agent to boost both permeability and selectivity. Cross-linking occurs without modifying the polyimide backbone, suppressing plasticization. At a 243:1 composition, phase separation is minimized, achieving a CO2 permeability of 799.5 barrer and a CO2/CH4 selectivity of 36.03. Applicable to natural gas/biogas purification and flue gas CO2 capture, it extends membrane replacement cycles and maintains stable separation efficiency.
This invention was developed with support from the Ministry of Education for the development of blue carbon biomass-based source materials and the establishment of a marine resource recycling platform.
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