【作者】 张颖；

【导师】 王世昌；

【作者基本信息】 天津大学 ， 化学工程， 2003， 博士

【摘要】 CO₂等酸性气体的膜分离技术研究已成为最受世界瞩目的关于能源和环境问题的重大课题之一。固定载体膜是一类很有发展前景的新型分离膜，而分离CO₂的固定载体膜尚属一崭新的研究领域，无论是膜材料的开发还是传递机理的探索都是亟待解决的问题。本文正是以此为背景，在高透过选择性CO₂固定载体膜材料的开发以及CO₂在膜内的传递机理等方面进行了一些新的探索和尝试。通过分析待分离气体、高分子基材、活性载体以及水的相互作用，本文从促进传递体系的选择、高分子基材的选择以及载体的选择等几个方面提出了一些原则以指导CO₂固定载体膜的研制。基于这些原则，本文研制成功三种CO₂固定载体膜材料，聚N-乙烯基-γ-氨基丁酸钠（PVSA），N-乙烯基-γ-氨基丁酸钠-丙烯酸钠的共聚物（VSA-SA）以及羧甲基壳聚糖（CM-CS）。分别以上述三种材料为表层，以聚砜（PS）、聚醚砜（PES）、聚丙烯腈（PAN）超滤膜为支撑体制成复合膜。利用红外光谱（FTIR）、X射线衍射（XRD）、X-射线光电子能谱（XPS）、核磁共振（1H NMR）、元素分析、环境扫描电子显微镜（ESEM）以及化学滴定法等对三种材料以及制成的复合膜的物理化学结构和形态结构进行了分析，结果证明三种材料均含有仲胺或伯胺和羧基，复合膜表层致密光滑，与支撑层紧密结合。以CO₂/CH4体系为研究对象，考察了各种复合膜的透过选择性能，系统研究了各种因素如耦合效应、支撑膜材料及其平均截留分子量、铸膜液中杂质、不同的交联剂、交联时间、载体含量等对膜结构和性能的影响。结果表明，所研制的膜极具开发前景。PVSA/PS，VSA-SA/PS，CM-CS/PES三种复合膜表现出优异的CO₂透过选择性，其综合性能指标远高于国外报道的其它同类固定载体膜。如CO₂压力为5.1cmHg时，PVSA/PS复合膜的CO₂渗透速率和理想分离因子分别为1.47(10-4 cm3 （STP）cm-2 s-1 cmHg-1和155.9；CO₂压力为5cmHg时，VSA-SA/PS复合膜的CO₂渗透速率和理想分离因子分别为8.0(10-5 cm3 （STP）cm-2 s-1 cmHg-1和406.2；CO₂压力为5.3cmHg时，CM-CS/PES复合膜的CO₂渗透速率和理想分离因子分别为5.79(10-5 cm3 （STP）cm-2 s-1 cmHg-1和84.6。其原因在于膜内引入了可与CO₂进行可逆反应的载体—胺基和羧基，从而促进了CO₂在膜中的传递。以PVSA/PS膜为考察对象，对膜内传递机理进行了探索，提出CO₂在干膜的情况下，膜内同时发生两个过程，即一部分CO₂通过自由扩散，另一部分以溶质-载体反应物（RNH（CH2）3COO-·CO₂）的方式扩散，在加湿膜的情况下，一部分复合物转变成了易于移动的HCO3-。红外光谱和拉曼光谱的测试结果证实了上述机理。三种复合膜的性能稳定性良好。在进料气压力约57cmHg下，连续运行一周，仍能维持较好的分离因子和渗透速率。更多还原

【Abstract】 Separation and removal of CO₂ using membrane technology is one of the most important subjects about energy and environment. Fixed carrier membrane is a kind of promising separation membrane. However, CO₂ fixed carrier membrane is a new research field in which both the development of membrane material and the exploration of transport mechanism are urgent. This study made attempts to develop fixed carrier membranes with high performance for CO₂ removal and explore transport mechanism of CO₂ in the membranes.In view of the interactions of gases, polymeric membrane, carrier and water, the principles of selecting facilitated transport system, polymeric material and carrier were proposed. On the basis of these principles, three kinds of CO₂ fixed carrier membrane materials were prepared successfully, they are poly（N-vinyl-γ-sodium aminobutyrate）, poly（N-vinyl-γ-sodium aminobutyrate-co-sodium acrylate） and carboxymethyl chitosan. The composite membranes were developed respectively with the above three kinds of materials as active layers and polysulfone, polyethersulfone, polyacrylonitrile ultra-filtration membranes as the supports. FTIR（Fourier Transform Infrared Spectroscopy）, XRD（X-ray diffractions）, XPS（X-ray Photoelectron Spectroscopy）, 1H NMR（Nuclear Magnetic Resonance）, elemental analysis, ESEM （Environmental Scanning Electron Microscope） and titration were employed to characterize the physical and chemical structure of the polymer and the morphology of the composite membrane. The results show that all of the materials contain secondary amine or primary amine and carboxyl groups and the active layers of the composite membranes are dense and smooth. The permselectivities of different composite membranes were measured with pure CO₂ and CH4 gas as well as binary mixture of CO₂ and CH4. The effects of many kinds of factors such as "coupling effects", material and molecule weight cut-off of the support membranes, the impurities in the dope solution, cross-linker, cross-linking time and carrier content were discussed in detail. The encouraging results were achieved. PVSA/PS，VSA-SA/PS and CM-CS/PES composite membranes present excellent comprehensive performances which are better than that of other fixed carrier membranes reported in literatures. For example, at 5.1cmHg of CO₂ pressure，PVSA/PS composite membrane displays a CO₂ permeation rate of 1.47(10-4 cm3 （STP）cm-2 s-1 cmHg-1 and CO₂/CH4 ideal separation factor of 155.9, at 5cmHg of pressure, VSA-SA/PS composite membrane displays a permeation rate of<WP=5>8.0(10-5cm3 （STP）cm-2 s-1 cmHg-1 and ideal separation factor of 406.2, at 5.3cmHg of pressure, CM-CS/PES composite membrane displays a permeation rate of 5.79(10-5cm3 （STP）cm-2 s-1 cmHg-1 and ideal separation factor of 84.6. The main reason is the introduction of the carrier, amine group and carboxyl group which can react reversibly with carbon dioxide in the membranes. The transport mechanism of CO₂ in PVSA/PS composite membrane was explored. In dry membrane CO₂ was transported in two ways, dissolved CO₂ and the complex （RNH（CH2）3COO-·CO₂）of CO₂ and carriers. While in humidified membranes, part of complex was transformed into small and easy to move ion HCO3-. The above mechanism was further characterized by FTIR using attenuated total reflectance techniques and FT-Roman spectrum.The stability of three kinds of membranes performance is good. The membranes can keep good separation factor and CO₂ permeation rate for one week at the feed gas pressure 57cmHg.更多还原