Synthesis Of Amino Acid Functionalized Ionic Liquids And Its Modification For Gas Separation Membranes

The increase of CO₂concentration in the atmosphere will lead to the greenhouse effect,which will cause sea level rise and unpredictable extreme weather.And CO₂is also an important source of carbon,so the capture and utilization of CO₂becomes one of the important initiatives to achieve carbon neutrality.Among various CO₂separation methods,membrane separation technology stands out with its advantages of high efficiency,environmental protection and low cost.In this thesis,we firstly synthesized1-butyl-3-methylimidazolium lysine ionic liquid（[Bmim][Lys]）,and prepared[Bmim][Lys]by ion exchange method using 1-butyl-3-methylimidazolium hexafluorophosphate and lysine as raw materials.The characters of infrared and ¹H NMR spectra,UV spectra,and X-ray diffraction analysis have been done,and the analysis results showed that amino acid ionic liquid（AAIL）has been successfully synthesized.Next,the synthesized AAIL was added to polyether block polyamide（Pebax 1657）as a blending additive to improve the relationship between gas permeability and selectivity by preparing blended membranes containing different amino acid ionic liquid（AAIL）contents.Since amino acid ionic liquids contain bis-amino groups,they can improve the performance of gas separation membranes by promoting the transfer of CO₂in the membrane through the interaction of bis-amino groups with CO₂acid-base.The AAIL/Pebax blended membranes were first characterized by FT-IR,XRD and TGA.The effects of AAIL content,feed pressure and operating temperature on the performance of the gas separation membranes were also investigated.The results of FT-IR analysis showed that physical co-blending of AAIL and Pebax membranes occurred without chemical reaction.The results of gas separation performance of CO₂showed that the addition of amino acid ionic liquid led to the enhancement of both CO₂permeability and CO₂/N₂selectivity.When the mass fraction of AAIL was 0.8 wt%,the permeability coefficient of CO₂was 101.03 Barrer and CO₂/N₂selectivity was 91.84,which reached the optimum.Compared to Pebax 1657 pristine membrane CO₂permeability coefficient increased to 66.47%and CO₂/N₂selectivity increased to 86.14%,breaking through the 2008 Robeson upper bound.The AAIL was added to polyimide(Matrimid^?5218),and the AAIL/PI blended membrane was first characterized by FT-IR,XRD and TGA.The gas separation performance test was performed to investigate the effects of AAIL content,feed pressure and operating temperature on the gas separation membrane performance.The results of FT-IR analysis showed that AAIL/PI membranes were physically co-blended,and the gas separation performance test results indicated that the AAIL/PI co-blended membrane had better separation performance compared with the PI pure membrane.When the mass fraction of AAIL is 0.6 wt%,the permeability coefficient of CO₂is 10.89 Barrer and CO₂/N₂selectivity is 65,which is 44.63%and 62.17%higher than the permeability coefficient of CO₂and CO₂/N₂selectivity of PI pristine membrane,respectively.The Robeson’s upper bound of 1991was exceeded.In summary,it shows that the addition of AAIL to polymer membrane matrix is an effective method to improve the gas separation performance of membranes.