Preparation And Gas Permeation Properties Of IL@ZIF-8/PVIM/PI Mixed Matrix Membranes

CO₂ capture,separation and removal are important issues in the fields of environmental protection and energy.Membrane separation technology has the advantages for CO₂ separation with low energy consumption,simple process and easy amplification.However,traditional polymer membranes exist trade-off effect.In recent years,the mixed matrix membranes doped inorganic porous materials has become a research hotspot,and it provides a new way for the construction of high-performance separation membrane.Zeolite imidazolate frameworks（ZIFs）as a new type of inorganic porous materials,it offer an important opportunity and possibility for the development of high-performance mixed matrix membranes.In this paper,the functional latex containing imidazole ionic liquids and ZIF-8 was synthesized in-situ based on microemulsion,then the latex was doped into polyimide（PI）to prepare a mixed matrix membrane.Utilize the compatibilization and affinity of imidazole ionic liquids,and the affinity and porosity of ZIF-8,to realize CO₂preferential adsorption and rapid permeation in the mixed matrix membranes.The main research contents and results are as follows:had a certain the compatibilization,improvingZIF-8 nanoparticles were synthesized by solvothermal method,and ZIF-8/PVIM latex was prepared by solution polymerization of 1-vinylimidazole（VIM）,and then the latex was doped into PI to prepare ZIF-8/PVIM/PI mixed matrix membrane.The morphology,gas adsorption and permeability of IF-8/PVIM/PI mixed matrix membranes were study,and the result shown that the compatibilization of PVIM could promote the dispersion of ZIF-8 nanoparticles in the mixed matrix membrane.Based on the framework pore structure of ZIF-8,CO₂ affinity of PVIM and ZIF-8,which effectively enhances CO₂ preferential adsorption and permeability of ZIF-8/PVIM/PI mixed matrix membrane.The CO₂ permeability coefficient(P_CO2)of ZIF-8/PVIM/PI mixed matrix membrane was greater than 480 Barrer,the permeability selectivity of CO₂/N₂（α_P（CO₂/N₂））and CO₂/CH₄（α_P（CO₂/CH₄））were more than 30,which were more than 4.5,2.0 and 2.0 times higher than that of pure PI membrane respectively.Because the compatibilization of PVIM was finite,when the amount of ZIF-8/PVIM latex doping was large,ZIF-8 nanoparticles still had a serious agglomeration in the mixed matrix membrane.On the other hand,ZIF-8/PVIM latex was synthesized by solvent method combined with polymerization process,and there were not enough means to regulate the morphology and structure of ZIF-8 nanoparticles,and ZIF-8/PVIM doping to improve CO₂ preferential adsorption and permeability of the mixed matrix membrane was limited.Aiming at the shortcomings of the above ZIF-8/PVIM doped mixed matrix membrane,based on the excellent CO₂ affinity of imidazole ionic liquids,and can promote the compatibilization between ZIF-8 nanoparticles and PI.The characteristics of microreactor of microemulsion,and can be used for the synthesis of inorganic nanoparticles,and the means of regulating nanoparticles are simple and diverse.In this chapter,polymerizable 1-vinylimidazole（VIM）was used as the oil phase,1-butyl-3-methylimidazolium trifluoromethanesulfonate ionic liquid（IL）as the surfactant,and zinc nitrate and methyl-imidazole aqueous solutions were used as the water phase to construct the inverse microemulsion system.ZIF-8 nanoparticles were synthesized by aqueous micelles of microemulsion,and IL@ZIF-8/PVIM latex were prepared by microemulsion polymerization,then IL@ZIF-8/PVIM latex doped into PI to prepare IL@ZIF-8/PVIM/PI mixed matrix membrane.The influence of the composition of the microemulsion on the morphology of ZIF-8nanoparticles,dispersion of ZIF-8 in IL@ZIF-8/PVIM/PI mixed matrix membrane,permeability P_CO2,P_N2,P_CH4 and permeability selectivityα_P（CO₂/N₂）,α_P（CO₂/CH₄）of the membrane were investigated,as well as effect of doping amount of IL@ZIF-8/PVIM latex on P_CO2,P_N2,P_CH4 andα_P（CO₂/N₂）,α_P（CO₂/CH₄）of the membranes were discussed.Research findings:（1）The particle size distribution of ZIF-8 synthesized by microemuision was between10-50 nm,and the average particle size was below 30 nm.（2）C_Zn（NO3）2 and C_{Me IM} in water phase of microemulsion have great influence on the permeability of IL@ZIF-8/PVIM/PI mixed matrix membranes.With the increase of the proportion of C_Zn（NO3）2 and C_{Me IM} in water phase,the number and size of IF-8 nanoparticles increased,The IL@ZIF-8/PVIM/PI mixed matrix membrane had more molecular diffusion mass transfer channels,better CO₂ affinity.And P_CO2of IL@ZIF-8/PVIM/PI mixed matrix membrane was also greatly increased,α_P（CO₂/N₂）,α_P（CO₂/CH₄）showed a trend of first increasing and then decreasing,but the degree of variety was small.（3）The mole ratio of H₂O,VIM and IL in microemulsion M_H2O/M_VIM/M_IL have a great influence on the permeability of IL@ZIF-8/PVIM/PI mixed matrix membranes.When the relative amount of VIM in M_H2O/M_VIM/M_IL increased,the relative amount of H₂O and IL would decreased,and the size of the synthesized ZIF-8 nanoparticles would decreased,The prepared IL@ZIF-8/PVIM/PI mixed matrix membrane had fewer molecular mass transfer channels,lower CO₂ affinity.And P_CO2 andα_P（CO₂/N₂）,α_P（CO₂/CH₄）of IL@ZIF-8/PVIM/PI membrane were decreased.（4）With the increase of IL@ZIF-8/PVIM latex doping amount in IL@ZIF-8/PVIM/PI membrane,P_CO2 of the membrane increased significantly,andα_P（CO₂/N₂）,α_P（CO₂/CH₄）appeared a trend of large increase at first and then decrease.（5）P_CO2 of IL@ZIF-8/PVIM/PI membrane was greater than 550 Barrer,α_P（CO₂/N₂）,α_P（CO₂/CH₄）reached about 45in the optimized composition of microemulsion and the latex doping amount.