Preparation And Gas Separation Properties Of Polyether Copolyamide CO₂ Separation Membrane

The problem of global warming caused by excessive emissions of greenhouse gases has attracted the attention of all countries in the world.As a big emitter of greenhouse gases,China has realized the importance of CO2 capture and storage(CCS)technology in Controlling CO2 emissions.Gas membrane separation technology is widely concerned because of its low cost,environmental protection and other advantages.According to different materials,membrane separation technology can be divided into organic membranes,inorganic membranes and blend membranes.The permeability and selectivity of organic membrane are restricted by each other;inorganic membrane materials have the disadvantages of high cost and high brittleness,which limit the application of organic membrane and inorganic membrane in industry to some extent.In order to overcome the shortcomings of organic membranes and inorganic membranes,the researchers explored and found the blend membranes,by mixing different materials to play the advantages of each material.According to the different materials,blend membrane can be divided into polymer blend membranes,mixed matrix membranes and other system blend membranes.Because polyethylene oxide(PEO)has a good affinity for CO2,Pebax 1657 with high PEO content is selected as the polymer substrate,and the appropriate polymer materials and inorganic fillers are selected to prepare the blend membrane.The study on the preparation of Pebax blend membrane shows that the polymer blend membrane is prepared by blending Pebaxl657 with high selectivity and Pebax2533 with high permeability,and Pebax 1657 and Pebax2533 are composed of Polyether Segment and polyamide segment,which greatly avoids the generation of interface defects.The experimental results show that the CO2 permeability and CO2/N2 selectivity of the blend membrane with 10%,30%and 50%Pebax2533 content are located in the upper right of the pure Pebax membrane line,closer to the upper limit of Robeson,so its comprehensive performance is improved compared with that of the single membrane.Using the adhesion of dopamine(DA)and polyethyleneimine(PEI)to modify the surface of halloysite nanotubes(HNTs),using the modified HNTs(PDH)as inorganic filler and pebax1657 as polymer substrate to prepare mixed matrix films,the results show that the hydrogen bond between PDH and pebax1657 has a limited effect on the movement of molecular chains to some extent.As the tubular structure of PDH is conducive to gas permeability,the CO2 permeability coefficient of hybrid membrane increases from 73.8 to 111 Barrer;the CO2 permeability coefficient and CO2/N2 separation coefficient are gradually close to the upper boundary of Robeson,and the gas separation performance is improved.The EPDH obtained by etching and surface modification of HNTs was used as inorganic filler,and Pebax1657 was used as polymer substrate to prepare mixed matrix membrane.The further study showed that the hydrogen bond between EPDH and Pebax1657 restricted the movement of molecular chain to a certain extent;and the CO2 permeability coefficient of the membrane increases from 73.8 to 101.5Barrer due to the gas transport pathway added by the surface channel of epdh The CO2 permeability coefficient and CO2/N2 separation coefficient moved to the right,close to the upper limit of Robeson,and the gas separation performance was improved.