Knowledge Management System Of Institute of process engineering,CAS
|Alternative Title||Preparation and CO2 Performance of Ionic Liquids Based Composite Membranes|
CO2的有效分离与捕集对于环境、能源、化工都有非常重要的理论意义和实用价值，因此设计开发出高效低能耗的CO2分离技术迫在眉睫。膜分离技术因其高效低能耗、环境友好等特点成为研究的热点。针对目前聚合物膜材料存在渗透性与选择性相互制约的问题，将离子液体与膜分离技术相结合，既能提高膜材料的分离性能，又能克服离子液体粘度大、成本高的问题。本文设计合成了一系列离子液体共混膜，同时引入了ZIF-8多孔材料来提高共混膜的分离性能及物理稳定性，并对其进行表征分析，研究不同材料之间的构效关系。本论文的主要研究内容和成果如下：（1）设计合成了一系列嵌段聚醚酰胺（Pebax）+离子液体（[Bmim][BF4]、[Bmim][DCA]、[Bmim][NTf2]）共混膜。物化性质表征结果表明：3种咪唑类离子液体与Pebax之间均是物理共混，且都具有较好的热稳定性；离子液体在共混膜中起到了增塑剂的作用，随着离子液体加入，膜的结晶度减少，自由体积增加。（2）研究了3种阴离子不同离子液体Pebax/IL共混膜的CO2分离性能。随着离子液体含量的增加，CO2渗透系数均大幅度提升，如在[Bmim][NTf2]含量为100%时，CO2渗透系数达到了157 Barrer，不同种类离子液体共混膜CO2渗透规律为：Pebax/[Bmim][NTf2]>Pebax/[Bmim][DCA]>Pebax/[Bmim][BF4]，与CO2在纯离子液体中的溶解规律一致，但是由于离子液体自身选择性较低使得膜选择性下降。（3）考察了ZIF-8的含量对Pebax/ZIF-8膜的结构及分离性能的影响。ZIF-8的加入使得膜的结晶度下降，且随着其含量的增加而在膜中出现团聚现象，形成无选择性“空穴”，促进气体在膜中的扩散。随着ZIF-8加入，共混膜对CO2的溶解系数及扩散系数都大幅度提升，但对于N2和CH4具有一定的“阻碍”作用。 （4）制备了一系列Pebax/ZIF-8/[Bmim][NTf2]三元共混膜，探究不同材料之间的构效关系。研究发现IL的加入对气体在共混膜中的分离具有两方面作用：少量的离子液体加入填充了ZIF-8与Pebax之间的无选择性“空穴”，阻碍气体扩散，CO2/N2选择性增加；较多含量的IL使得膜的结晶度减少，膜的自由体积增加，促进气体扩散，CO2/N2选择性减小。;Effective separation and capture of CO2 play a significant role in environment, chemical industry and energy. Thus a CO2 separation technology with high performance and low energy is imminent. Membrane separation technology has good application prospects due to its advantages on lower energy consumption, high efficiency, and environmental friendly. In view of the trade-off between permeability and selectivity for polymeric membranes, combination of ionic liquid (IL) and membrane separation technology can improve the gas separation performance of the membrane materials meanwhile overcome the high viscosity and consumption of the IL. In this paper, a series of IL-based composite membranes have been designed and prepared, and ZIF-8 porous materials have been introduced to improve the separation performance and physical stability of the composite membranes. The relationships between different materials have been also studied. The main research contents and achievements were summarized as follows:(1) A serious poly(ether-b-amide-6) (Pebax 1657) + IL composite membranes have been successfully synthesized and characterized. The IL are [Bmim][BF4]、[Bmim][DCA]、[Bmim][NTf2]. The results showed that the imidazolium IL were physically blended with Pebax and have good thermal stability. It reveals that IL acted as a plasticizer in the composite membranes. With an increasing IL content, the crystallinity of the membranes decreased and the polymer chain became more relaxed, resulting in a more amorphous structure and a higher FFV (fractional free volume) of membranes.(2) The CO2 separation performance of Pebax/IL composite membranes with different ionic liquids has been investigated. The results showed that CO2 diffusivity coefficients increased significantly with the addition of IL. The CO2 permeability of different composite membranes were in the order of [Bmim][NTf2] > Pebax/[Bmim][DCA] > Pebax/[Bmim][BF4], which were consistent with the solubility of CO2 in pure IL. While CO2/N2, CO2/CH4 selectivity decreased due to the intrinsically lower selectivity of IL itself(3) The influence of ZIF-8 addition on the structure and separation performance of Pebax/ZIF-8 membranes has been studied. The results showed that the crystallinity of membranes decreased with an increasing ZIF-8 content, and agglomeration occurred resulting in forming non-selective "voids". The addition of ZIF-8 increased the CO2 solubility coefficients and diffusion coefficientsof membranes, but it blocked the diffusion of N2 and CH4.(4) A series of Pebax/ZIF-8/[Bmim][NTf2] three-component composite membranes have been prepared and the relationships between different materials have been also investigated. It was found that the addition of IL had two effects on the gas diffusion: a small amount of IL could fill the non-selective "voids" between ZIF-8 and Pebax, hindering gas diffusion while CO2/N2 selectivity increased. And with the IL increased, IL could decrease crystallinity and increase the fractional free volume of membrane, facilitating gas diffusion while CO2/N2 selectivity decreased.
|李梦蝶. 离子液体复合膜材料的制备及其CO2分离性能的研究[D]. 中国科学院大学,2017.|
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