Preparation And Gas Separation Properties Of Ionic Hypercrosslinked Polymer Membranes And Derived Carbon Membranes

Gas separation is widely used in many fields such as chemical,energy,medical,food,pharmaceutical,etc.And the growing demand for gas separation technologies from the environmental point of view has made the development of efficient and cost effective gas separation technologies a focus of attention.Membrane technology is considered as a promising alternative method for separation and purification because membranes allow continuous and selective separation of different substances without phase separation.Compared with conventional gas separation technologies such as low temperature distillation,chemical absorption and adsorption separation,membrane technology is widely studied for its low energy consumption,flexible and simple operation,scalability and environmental friendliness.Therefore,the application of low energy consumption membrane technology to gas separation can achieve green and efficient separation.The development of high efficiency and low cost membrane technology for gas separation is indispensable.Thus,the development of materials with high permeability,high selectivity and long-term stability is essential for the widespread use of membrane separation technology.Based on this,this paper designs and prepares ionic hyper-crosslinked polymer membranes with novel chemical structures,and calcinates them into porous carbon membranes at high temperatures using them as precursors to further investigate the gas separation performance of the related materials.The specific research is divided into two parts as follows:（1）Based on Friedel-Crafts alkylation reaction and quaternization reaction,tris[4-（1H-imidazol-1-yl）-phenyl]amine（M₁）and 1,4-bis（bromomethyl）benzene(M_1-1)/4,4-dibromomethylbiphenyl(M_1-2)were selected as reaction monomers,and two new types of ionic hypercrosslinked polymers.The amount of catalyst was adjusted and the ionic hypercrosslinked polymer membranes A_M1-1-4 and A_M1-2-2 were prepared by vacuum assembly to obtain the optimum amount of material for membrane formation.Then,the chemical structures of the films were characterized by basic characterization means with a view to demonstrate the synthesis of the target structural products.The morphology and properties of the membranes were analyzed by scanning electron microscopy,thermogravimetric analysis,and tensile testing,indicating that the prepared membrane materials have smooth and dense surfaces,stable thermal properties,and good mechanical properties.In the gas separation test at35 ^oC,the hydrogen permeation factor of A_M1-1-4 membrane was 5.63 Barrer,and the ideal selectivity of H₂/N₂and H₂/CO₂were 8.16 and 3.13,respectively,indicating the potential of the material for gas separation applications.（2）With the polymer membrane as the precursor,the carbon membrane obtained by thermal decomposition has higher gas permeability and selectivity,and it is easy to break through the trade-off effect and achieve gas separation.Therefore,in this paper,the ionic hyper-crosslinked polymer membrane A_M1-1-4 prepared in the previous chapter was used as the precursor,and anhydrous cobalt chloride was used as the salt template to dope it into the precursor by immersion,and finally the porous carbon membrane was obtained by calcination at high temperature.The structure and morphology of the carbon films were analyzed by a series of tests.The final carbonization temperature of A_M1-1-700 at 700 ^oC had a Co metal content of 10.77 wt%,a microporous specific surface area of 122.1 m²g^-1,and a CO₂adsorption of 3.5 wt%at 298 K,which was significantly improved over the precursor.The H₂/CO₂selectivity of 5.30 at its H₂permeability factor of 3052 Barrer greatly exceeds the 2008Robeson upper bound,and the H₂/N₂selectivity of 7.18 is almost at the 2008 Robeson upper bound,indicating its promising application in gas separation.