【作者】 张建生；

【导师】 贺高红；

【作者基本信息】 大连理工大学 ， 膜科学与技术， 2009， 硕士

【摘要】 膜法制备富氧空气进行助燃可以极大的降低工业生产中的能耗,减少废气的排放,符合节能减排战略,具有较好的经济效益和社会效益,已成为膜分离领域研究的重点之一。实际生产中一般要求富氧量大,但氧气浓度要求不高,一般为25.0%～35.0%左右,这就要求这类富氧膜具有较高的氧气渗透速率,而对分离系数要求不严。富氧膜材料硅橡胶（PDMS）由于其极高的氧气渗透系数可以满足该种要求,从而得到广泛应用,但因其机械强度不高,一般将其复合在多孔支撑基膜上制备成复合膜使用。复合膜的性能除了和膜材料本身有关之外,还受到基膜结构的重要影响,因此,制备合适孔结构的基膜是制备高性能富氧复合膜的关键之一。论文以聚丙烯腈（PAN）为基膜材料,N、N-二甲基甲酰胺（DMF）为溶剂,水为凝胶介质,通过浸入沉淀相转化法制备基膜,以PDMS为选择层涂覆制备复合膜。通过使用有机添加剂聚乙烯吡咯烷酮（PVP）、不同分子量（400、600、1000、2000 g/mol）的聚乙二醇（PEG）和无机添加剂氯化锌（ZnCl₂）来调节基膜结构,制备具有合适孔径、孔隙率结构的多孔支撑基膜,保证涂覆后PDMS可以在基膜表面形成均匀、无缺陷的超薄致密膜,并提高PDMS/PAN复合膜的氧气渗透速率。首先对PAN浓度、涂膜方法、PDMS浓度等基本制膜条件进行了考察。结果表明,当PAN浓度为19.0%,PDMS浓度为4.0%（wt.%以后未加说明均为质量分数）时,可以制备性能较好的复合膜,其氧气渗透速率为292GPU,氧氮选择性为2.07。其次考察了添加剂对铸膜液热力学性质和凝胶动力学的影响。研究了铸膜液体系的相分离行为,测试了其浊点数据,进行（linearized cloud point,简称LCP）回归,计算制膜体系的理论双节线。结果表明,该体系热力学相行为符合LCP理论,随着添加剂PVP、PEG浓度及PEG分子量的增大,铸膜液的凝胶值减小,热力学稳定性减弱,分相加快。同时,随着添加剂PVP、PEG、ZnCl₂浓度及PEG分子量的增大,铸膜液粘度增大,成膜时透光率曲线起始部分的斜率绝对值逐渐减小,铸膜液凝胶速率减小,分相减缓。两种作用共同影响膜的结构。最后,通过扫描电镜对添加剂对基膜结构的影响进行了表征,并利用氧、氮纯气对复合膜的性能进行了测试。当添加分子量为400、600、1000、2000 g/mol的PEG浓度为6.0%、4.0%、2.0%、2.0%,PVP浓度为3.0%,ZnCl₂浓度2.0%时,复合膜均显示出优良的富氧性能,其氧气渗透速率分别为:407、352、377、521、410、490 GPU,其氧氮选择性分别为:2.07、2.10、2.09、2.07、2.01、2.03。(1GPU=10^-6cm³（STP）/cm²·s·cmHg)更多还原

【Abstract】 The oxygen-enriched air for combustion-supporting produced by the membrane separation,can reduce the energy consumption and the exhaust emission in the industry,which is to the great interest of energy-saving and emission-reduction strategy in our days.Therefore, it has brought considerable social and economic benefits,and thus,become a focus to the investigators.For oxygen-enrichment membranes to produce combustion air with low oxygen concentration of 25.0%to 35.0%,the oxygen permeation rate is more important than the selectivityof oxygen/nitrogen,which can be satisfied easily by poly（dimethylsiloxane）（PDMS） membranes.Therefore,it has been widely used to prepare oxygen-enrichment membranes for its excellent oxygen permeability coefficient.Nevertheless,its membrane-forming ability is so poor that its direct applications are limited.Consequently,PDMS has often been coated as the selective layer on porous polymeric substrates to form oxygen-enrichment composite membranes in practical applications.Moreover,not only the membrane material but also the structure of the substrate plays an important role in the performance of the composite membrane.As a result,to prepare the substrates with proper morphology is the key to the composite membrane with excellent performance.The composite membranes were prepared by coating PDMS on the surface of porous polyacrylonitrile（PAN） substrates,which were prepared via phase inversion process using PAN as the substrate material,N,N-dimethyl-formamide（DMF） as the solvent and water as the coagulant.To prepare the PAN substrate with proper pore size and porosity,which is helpful to form a thin defect-free PDMS dense membrane coated on the substrate surface,and to improve the oxygen permeation rate of the composite membranes,the organic additive of polyvinylpyrrolidone（PVP） and polyethylene glycol（PEG） with different molecular weight （400、600、1000、2000 g/mol） as well as the inorganic additive of zinc chloride（ZnCl₂） were used to control the structure of the substrate.Firstly,the membrane preparation conditions of the concentration of PAN,the coating method and the concentration of PDMS were investigated.It was shown that the composite membranes formed by coating PDMS solution of 4.0%on the substrates of 19.0%（wt.% following the same without any sepecial notes） PAN,exhibited good performance with the oxygen permeation rate of 292GPU,and the selectivity of oxygen/nitrogen of 2.07. Secondly,the effects of the additives on the thermodynamics properties and precipitation kinetics of the casting system were investigated.The cloudy points were measured and the experimental data were linearly regressed with the linearized cloud point（LCP） relation,by which,the theoretical binodal line was calculated.All the results showed that the systems in this study were in accord with the LCP relation and were suitable for membrane preparation. Moreover,the casting system became less thermodynamically stable for that the coagulation value decreased,with the increase of the concentration of PVP,PEG and the molecular weight of PEG,which improved the phase separation.However,when the concentration of the PVP, PEG,ZnCl₂ and the molecular weight of PEG increased further,the viscosity of the casting solution increased,and the precipitation rate decreased from the light transmittance curve, which delayed the phase separation.The structure of the membrane was the result of the both properties.Thirdly,the effects of the additives on the cross-section structure of the substrate membrane were characterized by scanning electron microscope（SEM）,and the gas permeation performaces were measured with the oxygen and nitrogen pure gas.It was shown by the results that the composite membranes with 6.0%of PEG 400,4.0%of PEG 600,2.0%of PEG 1000, 2.0%of PEG 2000,3.0%of PVP,2.0%of ZnCl₂ as the additives exhibited good oxygen-enrichment performance,such as the oxygen permeation rate of 407,352,377,521, 410,490 GPU as well as the selectivity of oxygen/nitrogen of 2.07,2.10,2.09,2.07,2.01,2.03, respectively.(1GPU=10^-6cm³（STP）/cm²·s·cmHg)更多还原