Preparation And CO₂Separation Property Of Modified Polyimide Membranes

Aiming at improving the gas separation performance of polymer membranes,three kinds of modified polyimide (PI)membraneswere prepared by doping andblending methods, and then utilized for CO2/CH4and CO2/N2separation. To bespecific, organic imidazole microcapsules (IMCs), sulfonated polyether ether ketone(SPEEK), and inorganic SiO2sphere were selected as additives. The interactionsbetween PI andthe aforementioned additives,the effects of additives onmembranestructures, physicchemical properties, and gas separation performance of themembranes were studied systematically.Inspired by structure and water retention ability of natural biological cells,organic imidazole microcapsules (IMCs) were prepared via distillation-precipitationpolymerization, and then were incorporated into polyimide (PI) to fabricate highperformance PI/IMCs mixed matrix membranes for separation CO2/CH4.The effectsof different PI/IMCs ratio and different operation conditions (humidity, pressure,temperature) on performance of membranes were studied systematically.The resultsshowed uniform dispersion of the embedded IMCs within membraneand goodcompatibilitybetween IMCs and the polymer matrix.The incorporation of IMCssignificantly reduced the crystallinity of polyimide membrane, improvedhydrophilicty of membranes surface, promoted the dissolution and transport of CO2inmembranes, and thus greatlyenhanced the performance of membranes. Among them,PI/IMCs-5membrane with5wt.%imidazole microcapsules exhibited the highestperformance with CO2permeability of193.3Barrer and a CO2/CH4selectivity of50.8.Sulfonated polyether ether ketone(SPEEK) was prepared by concentrated sulfuricacid sulfonating, and then were blended with polyimide (PI) to fabricate highperformance blending membranes PI/SPEEK for separation CO2/CH4and CO2/N2.The effects of different PI/SPEEK ratio and different operation conditions (pressure,temperature) on the structure, physicchemical properties and gas separationperformance of membranes were studied systematically.The results showedmembraneshaving the microphaseseparation behavior, increased hydrophilicty ofmembranes surface, improved water uptake of membranes, promoted the dissolutionand transport of CO2in membranes, and thus enhanced the permeability of membranes. Among them, PI/SPEEK6-80membrane exhibited the highest perfrmance469.8Barrer and CO2/CH4selectivity of47.3for separating CO2/CH4; with CO2permeability of456.25Barrer and CO2/N2selectivity of41.37for separating CO2/N2.Silicon dioxide(SiO2)was prepared by method of St ber, and then wereincorporated into PI and SPEEK blend polymer matrix to fabricate high performancePI/SPEEK-SiO2blend-hybrid membranes for separation CO2/CH4and CO2/N2.Theeffects of different polymer ratio, SiO2content and different operation conditions(pressure, temperature) on the structure, physicchemical properties and gas separationperformance of membranes were studied systematically. The results showed that, theembeded SiO2improved crystallinity of membrane, increased hydrophilicty ofmembranes surface, improved water uptake of membranes, promoted the dissolutionand transport of CO2in membranes and enhanced the performance of membranes.Among them, PI/SPEEK6-80-8%membrane exhibited the highest perfrmancewithCO2permeability of109.04Barrer and CO2/CH4selectivity of85.10forseparating CO2/CH4; withCO2permeability of116.32Barrer and CO2/N2selectivityof85.02for separating CO2/N2...