Preparation And Properties Of Gas Separation Membranes Based On Amino-poly(aryl Fluorenyl Ether Ketone)

During the past years,large amounts of CO₂ emissions mainly from industrial production and anthropogenic fossil fuels combustion.Excessive carbon dioxide poses a huge threat to our global health and environment.Thence,capturing and separating CO₂ are global problem that require to be solved urgently.Hence,the environmentally sensitive and energy-saving CO₂ separation technology is becoming essential giving it high prospects on large-scale industrial applications.Compare to other methods,membrane separation has plenty of advantages used for CO₂separation,such as high level of flexibility,low amount of energy used,as well as cheaper cost of operation.For this reason,it is urgent to develop a gas separation membrane having excellent permeability and selectivity.In this paper,we use poly?aryl ether ketone?polymers as the substrate material for gas separation membranes,because they have good mechanical properties,thermal stability and chemical resistance,which meet the conditions of use of gas separation membranes.In view of the poor gas permeability of the poly?aryl ether ketone?polymer itself,we chose to use a compound blending method to separately add inorganic carbon nanotubes and organic PIM-1 polymers to prepare a composite film or blend the membrane that has both advantages to improve the gas separation performance of the polymer membrane.In this paper,4-aminophenyl hydroquinone monomer was first prepared,and then poly-arylene ether ketone copolymer?Am-PAFEK?containing amino and fluorenyl groups was synthesized by the method of quaternary condensation polymerization.Mixed matrix membranes?MMMs?were fabricated by incorporating carboxylated multi-walled carbon nanotubes?MWCNTs?into a poly?arylene fluorene ether ketone?that contained amino groups?Am-PAFEK?matrix to improve CO₂separation performance.The combination of MWCNTs and Am-PAFEK exerted a favorable synergistic effect on the permeability and selectivity of membranes.The extraordinary smooth wall of MWCNTs acts as a highway through which gas passes,providing better permeability.The Am-PAFEK matrix itself has a dense internal structure that provides high gas selectivity.MWCNTs particles evenly distributed among the Am-PAFEK membrane due to the non-covalent bond interaction between the amino and carboxyl group.Efficient CO₂ transport pathways were constructed by homogeneous dispersion of MWCNTs with in MMMs,leading to maintained good selectivity and enhanced permeability.When the amount of carbon nanotubes added was 3 wt.%,that increased by above 60%in comparison to the Am-PAFEK membrane permeability,the CO₂/CH₄ and CO₂/N₂ selectivity of the Am-PAFEK/MWCNTs-3%membrane achieved 35.02 and 30.09,respectively.Therefore,the strategy of blending MWCNTs with Am-PAFEK exhibited a promising approach for improving gas permeability.In order to further improve the permeability of polyarylene ether ketone polymer film,PIM-1 polymer was synthesized by polycondensation reaction.The structure of PIM-1 was characterized by ¹H NMR and FT-IR spectral analyses.A series of flexible and transparent blending membranes were prepared by solution blending with different ratios of PIM-1 and Am-PAFEK.DSC and SEM analyses showed good compatibility between them.PIM-1 and Am-PAFEK in the blending membrane perform their respective functions.The former provides excellent permeability;the latter provides high selectivity for CO₂.Addition of 20%Am-PAFEK into the blending membrane increased the gas separation selectivity of CO2/CH4 and CO₂/N₂by 75%and 65%,respectively.The optimum separation performance was achieved by blending membrane with a CO₂ permeability of 752.4 Barrer and a CO₂/N₂ selectivity ratio of 26.7,extremely close to the Robeson upper bound?2008?.After 140-days aging test,the blending membranes still maintained above 70%CO₂ permeability,indicating that it has good antiaging properties.Consequently,the new type of membranes have great potential applications in industries.