【作者】 刘庆岭；

【导师】 邱介山； 王同华；

【作者基本信息】 大连理工大学 ， 化学工艺， 2008， 博士

【摘要】 膜分离技术作为二十世纪发展起来的一种多学科交叉的新兴分离技术，已广泛应用工业生产的各个领域。尤其是气体分离膜在清洁能源（氢能）的开发利用、温室气体CO₂的捕集、分离及回收利用、天然气的纯化以及空气分离等诸多方面有广阔的应用前景。炭分子筛膜（简称“炭膜”）是一种新颖的具有分子筛分功能的炭基膜材料，因具有较高的气体分离选择性、良好的热和化学稳定性，引起了各国科学家的极大关注和研究热情。但目前炭膜的气体渗透性较低，并仍然存在着气体分离膜难以解决的难题即气体的分离选择性与渗透性之间的矛盾关系。如何突破这一矛盾关系，制备出高渗透通量、高分离选择性的气体分离炭膜，是实现炭膜大规模产业化应用的关键与前提。从材料的结构设计出发，通过在炭膜前驱体前体中引入纳米尺度的功能基团，利用纳米粒子的界面和尺度效应，在微介观层面上合理设计炭膜前驱体的微结构与组成；调控炭膜的极微孔尺度与分布；赋予炭膜功能化；提高炭膜的气体渗透通量；实现高渗透通量、高选择性的新型功能炭膜的可控制备；是解决气体的分离选择性与渗透性之间的矛盾关系，实现炭膜产业化应用的重要途径。基于上述思路与构想，本论文以制各具有高渗透通量、高分离选择性的新型气体分离功能炭膜为研究目标，在炭膜前驱体的结构设计、制备方法以及炭膜的气体分离机理，功能基团的作用机制等方面进行了有益研究探索。取得了如下的创新研究成果：以无机纳米氧化物粒子（SiO₂，TiO₂）为功能基团，采用“溶胶-凝胶”技术制备了纳米氧化物／炭功能膜（第三章）。利用无机粒子间的孔道以及无机粒子与炭母体间产生的微相分离所形成的超微孔，增加气体分子在炭膜中渗透、扩散通道，提高炭膜对气体的渗透能力。结果表明：纳米氧化物粒子及其无机网络结构增强了膜的气体渗透性能，所制备的TiO₂杂化炭膜对单组分O₂，渗透系数为520．30 Barrer，O₂／N₂分离系数达到8．4。该类材料的成功制备为发展新一代的功能炭膜材料提供了新思路。尽管无机纳米氧化物的引入明显地提高了炭膜的气体渗透能力，但并没有很好的改善气体的渗透性与分离选择性的矛盾关系，其原因是无机纳米氧化物不属多孔材料，纳米粒子本身无法提供气体的渗透通道。为此，在第四章中，我们以具有规则、有序孔道结构的纳米沸石分子筛（4A、ZSM-5、T）为功能基团，成功地设计制备出系列沸石分子筛／炭杂化功能炭膜。利用其发达有序的微孔通道及纳米粒子与炭母体间所形成的界面间隙（超微孔结构），实现气体在炭膜中的快速渗透，提高炭膜的气体渗透性。结果证明：沸石分子筛的引入，在保持较高的气体分离选择性的条件下，大幅度提高了炭膜的气体渗透性；并发现沸石分子筛的种类、含量、粒度以及炭化工艺条件对功能炭膜的气体分离性能有决定性影响。经工艺条件的优化设计，以纳米级ZSM-5为功能基团制备的ZSM-5杂化炭膜，对O₂的渗透系数达到671．23 Barrer，O₂／N₂分离系数达11．4。并实现了在温和可控的条件下，通过控制ZSM-5的含量、粒度及炭化工艺条件来调控炭膜的极微孔尺度和分布，制备高渗透通量、高分离选择性的功能炭膜。为了提高炭膜对特定气体分子的“分子识别”能力及渗透选择性能，实现其对气体混合物的有效分离，本论文试图在炭膜中引入了一些具有特殊作用的功能基团，以增强特定气体分子在炭膜中的渗透、扩散能力。如为了提高CO₂分子在炭膜中的渗透、扩散能力，选用对CO₂分子具有较强的吸附、扩散能力的T型分子筛为功能基团，成功地制备了T／C功能炭膜。结果表明：分子筛的晶体粒度和形态对所制备的T／C功能膜的气体分离性能有很大的影响，采用小晶体粒度的T型沸石分子筛制备的T／C功能膜对CO₂／CH₄混合气中CO₂的渗透系数达到1 532 Barrer，CO₂／CH₄分离系数达到179，功能炭膜的气体分离系数可以通过调整分子筛的晶体粒度和形态来控制。为了进一步的提高气体在功能炭膜中的渗透、扩散速率，我们对引入的功能基团进行了“扩孔”，设计并制备以有序介孔材料为功能基团的SBA-15／C和MCM-48／C功能炭膜，在炭膜母体中形成“介孔-微孔”复合孔结构体系。利用气体分子在介孔材料孔道中的快速传输作用，增加气体在炭膜中的渗透性能（第五章）。研究表明：有序介孔材料提供的宽阔、畅通的孔道体系，可以实现对小气体分子的快速扩散。并发现引入具有三维孔道体系的MCM-48功能炭膜对气体分子的输送能力要明显高于引入二维孔道体系的SBA-15功能炭膜，MCM-48／C功能膜对H₂，CO₂，O₂的平均渗透系数分别可达到3838．22，2508．01，527．12 Barrer，CO₂／CH₄，CO₂／N₂，O₂／N₂的理想分离系数分别达到：100．3，39．2，8．2。气体分子在炭膜中的分离机理是基于努森扩散辅助的“分子筛分”机理。这为进一步探索该类具有独特“介孔-微孔”复合孔道体系的功能膜材料的研究奠定了基础。碳纳米管与有序介孔炭材料是近年来出现的新型纳米炭材料，它们的特殊结构特征显示它们对气体分子具有很高的传输能力。在第六章，我们将碳纳米管和有序介孔炭CMK-3材料引入炭膜前躯体，制各了碳纳米管／炭和有序介孔炭／炭功能炭膜。研究发现：碳纳米管／炭功能炭膜的气体渗透性有明显提高，但其分离系数有所降低。有序介孔炭CMK-3的掺杂量以及恒温时间对所制备的CMK-3／C功能膜气体渗透性能有重要影响。CMK-3含量增加，气体渗透系数增大，理想分离系数减小；而炭化恒温时间的则与其相反。本论文对对新型的炭／炭复合型炭膜的探索将进一步拓宽功能炭膜的的研究领域，对构建新型的炭膜结构，对实现高渗透、高选择性功能炭膜的可控制备具有重要意义。更多还原

【Abstract】 Membrane separation technology is a new and interdisciplinary separation technology developed in the 20th century, which has been widely investigated and used in the world. Especially, membrane-based gas separation technology has attracted much attention in various fields such as the developing and utilization of clean energy （H₂）, the greenhouse gas carbon dioxide separation and recovery, the natural gas purification and oxygen/nitrogen separation. Carbon molecular sieving membrane （Carbon membrane） is a novel inorganic membrane material with molecular sieve ability, and it has attached more attention owing to its high selectivity, thermal stability and good chemical stability. However, the strong trade-off relationship between the gas permeability and selectivity make it impossible to satisfy the industry requirement. How to solve the trade-off bottleneck problem and to prepare high performance carbon membranes is a key point for its industrialization.One important approach to solve the challenging task mentioned above is to design the structure of the precursor by incorporating functional groups and to tune the ultramicropores distribution using the "interface effect" formed between the membrane matrix and the functional groups.In this dissertation, in order to prepare high performance carbon membranes with high gas permeability as well as high permselectiviy, valuable explorations have been carried out on designing the structure of the precursor, developing new synthetic strategies and investigating the gas separation mechanism of the as-synthesized membranes. The main results are summarized as below:A novel nano-oxide/polyimide organic precursor is designed and prepared based on the "sol-gel" technique, which is used to produce nano-oxide / carbon composite membrane （Chapter 3）. The interfacial gaps between inorganic particles and the carbon phase are believed to help to increase the gas diffusion ability and to improve the gas permeability. As such the gas permeability of the as-synthesized composite membrane is significantly improved. For single gas test, the composite membrane has an intrinsic O₂/N₂ selectivity of 8.4 with O₂ permeability of 520.30 Barrers. The fabrication of this kind of membrane material provides a new impetus to developing new generation of "inorganic-inorganic" composite membranes. In order to improve the gas permeability without decrease the selectivity of the synthesized membrane material, novel carbon/zeolite membrane materials are designed and prepared by incorporating zeolites （4A, ZSM-5, T） into the membrane precursors （Chapter 4）. The micropores of the zeolite and the interfacial pores between zeolite and carbon will help the gas diffusion and increase the gas permeability. The results show that the membrane separation performance is affected by the zeolite type, zeolite loadings, the particle size and the pyrolysis parameters. The permeability of O₂ in ZSM-5/carbon membrane （10wt. %, 700℃） is 671.23 Barrer with the O₂/N₂ selectivities of 11.4. This kind of functional membrane can be able synthesized by tuning the zeolite loadings and the pyrolysis temperatures.In order to separate CO₂/CH₄ gas pairs, zeolite T/carbon membranes were prepared by incorporating zeolite T into the carbon matrix. The gas selectivity （CO₂/CH₄） of the membranes for both single gas and mixed-gas （CO₂/CH₄: 50/50 mol. %） can be controlled in a wide range by changing the zeolite T particle size and morphology without altering the final pyrolysis temperatures and zeolite loadings.In chapter 5, mesoporous material/carbon membranes are designed and prepared by incorporating SBA-15 and MCM-48 into the polyamic acid. The results show that the as-prepared membranes show excellent gas separation performance compared to pure carbon membranes, which indicated that the wide pore size of the mesoporous materials help improve gas diffusion rate in the membranes. The MCM-48/carbon membrane shows higher gas permeability than that of SBA-15/carbon membrane. The permeabilities of pure gas H₂, CO₂, O₂ in MCM-48/carbon membrane are 3838, 2508, 527 Barrer, and the selectivity of CO₂/CH₄, CO₂/N₂, O₂/N₂ are 100.3, 39.2, 8.2, respectively. The main gas separation mechanism of the functional membrane is "Knudsen Diffusion assisted molecular sieving mechanism". These kinds of membrane materials are expected to bring new opportunities for preparation of unique "mesoporous - microporous" composite membranes.Carbon nanotubes （CNTs） and ordered mesoporous carbon are novel carbon materials; however, they cannot separate gas molecules effectively. In chapter 6, multi-walled carbon nanotubes （MCNTs） and ordered mesoporous carbon CMK-3 are chosen as fillers to prepare MCNTs/C and CMK-3/C membranes. The results show that the loading of CMK-3 and the holding time at final pyrolysis temperature significantly affect the gas separation performance of the CMK-3/C membranes. The gas permeabilities of the CMK-3/C functional membranes increase with the CMK-3 loading increase as well as decrease the holding time. This research is expected to broaden the research field of carbon membranes and it is helpful for controlled synthesis of high performance carbon membrane materials.更多还原