【作者】 于云武；

【导师】 姜振华；

【作者基本信息】 吉林大学 ， 高分子化学与物理， 2014， 博士

【摘要】 随着对聚合物气体分离膜研究的深入进展，透过性和选择性之间的矛盾关系逐渐被人们意识到。单纯从改变聚合物链自由体积的角度出发，提高聚合物膜的气体分离性能，很难同时提高其透过性和选择性，透过性的提高，通常是以牺牲选择性为代价的。本论文工作主要是围绕如何提高气体分离膜整体性能展开。首先，通过分子设计引入分别可以增大自由体积和促进传递的基团，改善聚芳醚的气体分离性能，期望达到透过性和选择性的最有平衡；其次，采用二氧化钛纳米粒子和多壁碳纳米管为分散相制备混合基质膜，综合无机分散相和聚合物基体的优势，进一步提高气体分离性能；最后，以含氟聚醚醚酮为制膜材料，采用干湿相转化法制备具有致密皮层和多孔支撑层的非对称膜，与均质膜相比，非对称膜具有更好的透过性，而致密皮层的存在保持了良好的选择性。更多还原

【Abstract】 Energy and environmental issues have become two major problems that thepeople all over the world have to face—it is also an important issue during theeconomic and social development of our country, especially the crisis of globalwarming caused by CO2and other greenhouse gases. So it is imminent that reducingenvironmental pollution, improving energy efficiency and shifting the way ofproduction and life. Compared to the traditional method—cryogenic and pressureswing adsorption process for gas separation, membrane technology has been subjectto widespread attention, owing to no phase change, low energy consumption, simpleequipment, convenient and flexible operation, etc. Gas membrane separationtechnology has been used in air separation for oxygen and nitrogen enrichment,hydrogen recovery, CO2separation and adsorption, natural gas dehydration,olefins-paraffin separation, etc. Commercialized gas separation membrane materialsare silicone rubber, cellulose, polysulfone and polyimide. Compared togeneral-purpose plastics, poly(aryl ether) could be adapted in high temperature andpressure environment and may be used for separation and adsorption CO2, SO2, H2Sand other acidic gases because of its outstanding chemical stability, thermal stabilityand mechanical properties, and resistance to plasticizing properties and resistance toacid.Taking the design idea of this thesis as the starting point, the trifluoromethyl(-CF3) and amino (-NH2) were introduced into polyethersulfone to improve the gasseparation performance. The three series of polyethersulfone containingtrifluoromethyl and amino were gotten by changing the type and proportion of thefluorine-containing bisphenol and amino polyether sulfone. Chemical structure ofpolymers was characterized by IR and NMR. DSC and TGA results indicated that each polymer in three series had a high glass transition temperature and good thermalstability. These polymers exhibited higher tensile strength and Young’s modulus butlower elongation at break. The high electron density of the fluorine atom made thebulk density of polymer chains decreased, so that the fractional of free volume of thepolymer increased. The fractional of free volume decreased with the introducing ofamino group and the decreasing of trifluoromethyl, and then the permeabilitycoefficients of N2and O2decreased. Lewis acid-base interaction between-NH2andCO2molecules in the polymer could improve the solubility coefficient of CO2,thereby increasing the CO2transmission rate through the membrane. The promotionof-NH2to CO2permeation offset the CO2permeation rate decreasing caused by thereduced free volume, so that the permeability coefficient P(CO2) reduced slightly,even increased with increasing of the amino segment ratio. However there was nosuch a interaction between-NH2and O2, N2and other non-polar gases, so the impacton gas separation was limited. Because the ideal separation factor is ratio ofpermeability coefficients of the fast gas and the slow gas, the gas separation factor ofCO2to other gases were improved.Preparation of the mixed matrix membrane (MMM) and the asymmetricmembrane has been an effective way to improve the gas separation performance. Asintroducing of the mixed inorganic particles into the polymer matrix, the MMMpossesses the advantages of both the polymer matrix and the inorganic particles. Dueto the diversity of inorganic particles, we have more choices in improvement of theperformance of gas separation membranes, and the permeability and separation factorcould be improved simultaneously. In this thesis, the titanium dioxide nanoparticlewas used as inorganic dispersed phase to improve the gas separation performance ofmembranes. The interaction between inorganic particles and the polymer chains willreduce the entanglement between polymer chains and hinder the movement of thepolymer segments, so that the bulk density decreases, the diffusion coefficient ofMMM will increase, thus the gas permeation rate will be improved; on the other hand,the interaction between the hydroxyl groups on TiO2nanoparticles and CO2moleculescould promote the transfer of CO2. Scanning electron micrographs of MMM observed that TiO2nanoparticles dispersed even in the polymer matrix, it could be attributed tothe good affinity between hydrophilic TiO2nanoparticles and a water soluble solventNMP. The hydrogen bonds between the hydroxyl groups on TiO2nanoparticles and-NH2groups were beneficial to TiO2dispersion. EDX test results for AmFPES-TiO2mixed matrix membranes obtained a signal of element Ti; three peaks reflectingdifferent TiO2crystal types appeared in XRD test results. Since the introduction ofTiO2nanoparticles to the MMMs led to decreasing of tensile strength and breakingelongation of mixed matrix membranes compared with the dense films. The gasseparation performance analysis showed that the introduction of TiO2nanoparticlesreduced bulk density of the polymer chains and the gas permeation coefficientincreased obviously. The interaction between hydroxyl groups on TiO2nanoparticlesand CO2molecules improved the permeability coefficient while improved CO2separation factor with respect to other gases.We selected Am-6FDA-PES-20and Am-6FDA-PES-60as polymer matrix,acidification modified multi-walled carbon nanotubes as dispersed phase, andprepared AmFPES-MWNT mixed matrix membranes by solution blending method.The acidulated MWCNTs were characterized by IR spectroscopy, and we couldobserve enhancement of carboxyl characteristic absorption peak indicating that thecarboxyl content increased after acid treatment. The microstructure of the mixedmatrix membranes were characterized by scanning electron micrograph. At lowaddition amounts, MWNT-COOH dispersed well in the polymer matrix and contactedclosely with the substrate. When the addition amount of increased to5wt%, a largeamount of carbon nanotube clusters appeared. The gas separation performanceanalysis for AmFPES-MWNT mixed matrix membranes, showed that as theMWNT-COOH was added into the mixed matrix membrane, the gas permeabilitycoefficients improved significantly. This is because carbon nanotubes withsize-controllable one-dimensional hollow structure provid a good channel fordiffusion of gas molecules.Preparation of asymmetric membrane by dry-wet phase inversion is an importantway to improve the gas separation performance of membrane materials. Asymmetric membranes generally consisted of a dense skin and a porous support layer thatproviding the separation performance and supporting respectively. The gaspermeability of the asymmetric membrane could be improved by the porous structureof the support layer. In this thesis, we used3FPEEK to prepare asymmetricmembranes, dichloromethane as solvent and alcohol as additive. The cross-sectionmorphology of asymmetric membranes was characterized by SEM. When the additiveof n-butanol was at a low amount, the support layer was a sponge-like structure. Themacroporous layer appeared at a lower amount when isobutanol, t-butanol andisopropanol were used as non-solvent addition. The surface morphology androughness of asymmetric membranes were characterized by AFM. The porosity ofasymmetric membranes obtained by gravimetric method showed that in the case ofthe same type of alcohol additive, the porosity increases with increasing of additiveamount. Compared with the dense3FPEEK membrane, the tensile strength andYoung’s modulus of asymmetric membranes with a porous support layer decreased,but the elongation at break increased obviously, the maximum could increase from8.13%to49.93%. Mechanical properties of asymmetric membranes prepared in thisthesis could meet the strength requirement in the gas separation process. Since theporous support layer promoted a substantial increase in gas permeation rate ofasymmetric membranes comparing with the dense film and it could be attributed tothe porosity increase. The presence of dense skin of asymmetric membranesmaintained a good separation performance, CO2/O2separation factor significantlyincreased.更多还原