Optimization Model And Molecular Simulation Of CO₂ Separation Mechanism In Ionic Liquid Composite Membrane

Carbon dioxide?CO₂?is one of the main greenhouse gases,and reducing its emissions is crucial.Carbon capture,utilization and storage technology is one of the effective methods to reduce CO₂ emissions,where CO₂ capture is a key step in the entire process.At present,ionic liquid blend membranes have a very good effect in the separation of CO₂.Researchers have carried out a large number of experimental studies,but the related mechanism research is relatively small.The study of the mechanism of CO₂ separation can improve the separation efficiency and provide very important guiding significance for the design of membrane materials.Therefore,in this paper,the ionic liquid blending membrane is taken as the research object,and the microscopic mechanism of the ionic liquid blending membrane and its interaction with CO₂ are studied by molecular dynamics methods.The research content and conclusions are as follows:?1?Molecular dynamics simulations were performed with different water contents?30%,55%,70%?and[Bmim][B?CN?₄]ionic liquid blend system,and ionic liquids containing different types of anions?[Bmim][B?CN?₄],[Bmim][Tf₂N],[Bmim][PF₆]?were simulated with a water blending system to investigate the microscopic mechanism of the blending system and its effect on CO₂ separation.From the results of the self-diffusion coefficient and the number of hydrogen bonds,it can be known that as the water content increases,the diffusion coefficient of anions and cations gradually increases.This is because the addition of water destroys the hydrogen bond network between the anions and cations and causes the interaction to gradually reduce.Compared with the two ionic liquids[Bmim][Tf₂N]and[Bmim][PF₆],the larger self-diffusion coefficient of[Bmim][B?CN?₄]may be due to the small interaction between anions and cations.With the increase of water concentration,the self-diffusion coefficient of ionic liquids gradually increases,and the diffusion coefficient of ionic liquids with higher water solubility increases significantly.The interaction between anions and water is stronger than the interaction between cations and water,and the interaction between anions and CO₂ is stronger than the interaction between cations and CO₂.?2?Molecular dynamics of[Bmim][Tf₂N]ionic liquids?10wt%,20wt%,30wt%,35wt%,40wt%,50wt%,and 100wt%?with 6FDA-TeMPD?PI?composite membrane simulation.The results show that as the concentration of[Bmim][Tf₂N]increases,the ionic liquid regions gradually connect and form continuous channels.The interaction between PI and anion is stronger than the interaction between PI and cation.As the concentration of ionic liquid increases,the number of hydrogen bonds between PI-cation and PI-anion gradually increases.Due to the shielding effect of the ionic liquid,the number of hydrogen bonds between the PI chains decreases as the concentration of the ionic liquid increases.The decrease of the self-diffusion coefficient of CO₂ is attributed to the decrease in the free volume fraction of the[Bmim][Tf₂N]/PI blend system with the increase of the ionic liquid,and the ionic liquid acts as a barrier to diffusion.The increase in CO₂ self-diffusion coefficient is due to the formation of continuous ion channels at higher ionic liquid concentrations,and[Bmim][Tf₂N]has played a role in promoting diffusion.The research contents and conclusions of this article explore the mechanism of CO₂separation by ionic liquid blend membranes at the molecular level,analyze the influence of the microstructure of the blend membrane on the separation effect,and provide a theory for designing more efficient separation membrane materials.support.