Study On Synthesis And Membrane Separation Properties Of Novel Polyimide

Nowdays,the adverse effects on the environment and human health by large amounts of CO₂produced by human production activities have attracted widespread attention,which is one of the greatest global issues we face currently.Thus,the capture and storage of CO₂ is an effective way to prevent the rapid rise of CO₂ concentration.The membrane-based gas separation technique is recognized as an effective method for the selective removal of CO₂ compared with other technologies due to its advantages of facile operation mode high energy efficiency,green and energy saving,small carbon footprint.At present,the type of farmiliar membrane material is polymer materials（such as polyimide）,which frequantly possess high selectivity and low gas permeability.So this topic from the perespective of molecular design,firstly,a novel diamine was designed and synthesized and to prepare a series of polyimide.Then we prepared three types of mixed matrix membranes based on MOF and COF with abundant organic structure,which improve the CO₂ permeability and maintain the the high selectivity of CO₂.The work paly a exploring role in industrial application of membrane speparation of CO₂.The main contents are as follows:（1）A series of novel polyimide was prepared via diamine monomer 3FDPA with varieties of commercial dianhydride monomers.Then polyimides were tested and cpmpared with each other about thermostability,hydrophobic performance,solubility and gas separation performance.The results show that the polyimides have excellent thermal properties,high hydrophobic performance,good solubility.（2）In this work,the UiO-66-NH₂ nanometer materials was synthesized via a facilely hydrothermal synthesis method,which shows the high CO₂ uptake capacities.Then the prepared UiO-66-NH₂ was dispresed in the matrix with excellent comprehensive properties（PI-1）to synthesis a series of PI-1/UiO-66-NH₂（x）MMM with different content of UiO-66-NH₂.The large specific surface area of UiO-66-NH₂ combined with matrix PI-1 to enhance CO₂ permeability.Compared with pure PI-1,the MMM consists of 10wt%UiO-66-NH₂ filler show the highest CO₂ permeability increased by 99.4%and get to 19.72 Barrer.Meanwhile,the CO₂/CH₄ selectivity is 53.4 and remain unchanged.（3）The UiO-66-NH₂ was functionalized with melamine to obtained UiO-66-NH₂@Me nanoparticle.Which still maintain good thermal properties,large specific surface area,unique pore structure and more amino groups and nitrogen sites compared with UiO-66-NH₂.Then UiO-66-NH₂@Me was dispresed in the PI-1 matrix to prepare the MMM.The CO₂ permeability and CO₂/CH₄ selectivity is 16.83 Barrer and 57.12,the MMM enhanced 70.17%and 9.17%respectively.（4）This paper was the preparation of Schiff-base covalent organic frameworks（COF）GDX-1.The various filler content PI/GDX（x）mixed matrix membranes were prepared.The results showed that GDX-1was well dispersed in the PI-1 matrix and the addition of fillers had essentially no effect on the structure and thermal properties of PI-1,Meanwhile,with the increase of GDX-1,the permeability coefficients of CO₂ and CH₄ gases increase.Compared with the pure PI-1 membrane,PI-1/GDX（x）showed an increment of 19.07%in ideal selectivity of CO₂/CH₄ and an enhancement of 130%in CO₂ permeability at 10 wt%GDX-1.