Synthesis And Performance Of Grafted Polymerized Ionic Liquids For CO₂ Separation Membranes

It is very important to capture CO2 to remission global warming.Polymeric ionic liquid(PILs)is now attracting much attention with excellent CO2 solubility and mechanical and chemical stability of polymer.Traditional PILs is synthesized by polymerization of ionic liquid monomer,however,the ionic liquid which can be polymerizable is infrequent and expensive with bad film forming ability.In this work,polysulfones was a basic material,the cations with different chemical structures was grafted on it.Different polymerized ionic liquids is synthesized by ion exchange reaction.The membrane shows excellent CO2/N2 separation performance.First,In this work,imidazolium-functionalized polysulfones(PSf-g-[MIm][Cl])were synthesized by simple and controllable chloromethylation-Menshutkintwo-step method.And PSf-g-[MIm][Cl] membrane was made by imidazolium-functionalized polysulfones as a separation layer and polypropylene(PP)as the supporting layer.The factor on seperation performance of the membrane,concentration of casting solution of the membrane,solvent evaporation temperature,degree of imidazolium,the operation temperature and pressure was researched.The results show that proper casting solution concentration(11 wt.%)and moderate solvent evaporation temperature(60 ?)is favorable to get excellent perm-selectivity.CO2 permeability and CO2/N2 perm-selectivity increase in pace with the increasing of the degree of imidazolium.At 25 ?,0.4 MPa,degree of imidazolium 172%casting solution concentration 11 wt.%,and humid conditions,the membrane shows good CO2 permeability of 66.4 barrer and CO2/N2 perm-selectivity of 118.4.In order to study the influence of different anions on the separation performance of the polymeric membrane,PILs were made with different anions via ion exchange reaction with PSf-g-[MIm][Cl] as the basic material.The anions used are Ac-,BF4-and CO32-.The result is that the anion with proper alkalinity is favorable for the dissociation of CO2,which can get good separation performance.PSf-g-[MIm][Ac] shows the best performance of the tested membranes,At 25 ?,0.4 MPa,degree of imidazolium 172% casting,and humid conditions,the membrane shows good CO2 permeability of 100.9 barrer and CO2/N2 perm-selectivity of144.1.In order to further study the influence of the structure of the cations on separation performance,trimethylamine and triethylene diamine was used to make polymeric ionic liquids with quaternary ammonium,PSf-g-[TMA][Cl] and PSf-g-[EDA][Cl].PILs was prepared with PP as supporting layer and quaternary ammonium functionalized PSf as separating layer respectively.The results show that quaternary ammonium functionalized PSf has better separating performance than imidazolium.The temperature and pressure was study on the separation performance of PSf-g-[TMA][Cl].At 30 ?,0.4 MPa,degree of quaternization 156% casting,and humid conditions,the membrane shows good CO2 permeability of 64.9 barrer and CO2/N2 perm-selectivity of 96.9.