氧化铝中空纤维上ZIF-8膜的制备及气体分离性能研究

发布时间：2018-03-18 04:37

本文选题：ZIF-8膜　切入点：中空纤维管　出处：《浙江大学》2015年硕士论文　论文类型：学位论文

【摘要】：金属有机框架(Metal Organic Frameworks, MOFs)是一类由金属离子与有机配体形成的有机无机复合多孔材料,因其优异的比表面积以及光学特性等功能,近几年来一直都是研究的热点。类沸石咪唑框架(Zeolitic Imidazolate Frameworks,ZIFs)作为MOFs的一个重要子类,是由过渡金属(如Zn、In等)和含N的咪唑类有机物相互交联形成的多孔材料,其骨架为类似沸石分子筛的空间网状拓扑结构,且具有极大的比表面积、特定的孔道结构以及优良的热稳定性和化学稳定性,因而在膜材料研究领域具有非常广阔的应用前景。目前ZIFs膜的研究已经经历一段高速的发展期,关于ZIFs成膜的研究层出不穷,然而主要是集中在片状载体上成膜或者分散于有机物中形成的复合膜,需要借助复杂的载体改性或者添加粘结剂等手段,并且得到的膜层普遍较厚,气体的通量不高,膜层性能受到制约,同时片状载体不适合制作膜组件,也不利于ZIF-8膜的大规模工业化应用。针对以上问题,本论文选用高孔隙率、大比表面积以及适合于工业化放大的氧化铝中空纤维管作为载体,研究其表面制备ZIF-8膜的影响因素。以自制的氧化铝中空纤维管作为载体,采用简便的晶种浸涂法在载体表面涂覆晶种层,通过二次生长法制备得到ZIF-8膜。重点考察了晶种大小、合成时间、合成配方等因素对成膜的影响。实验结果表明,由于ZIF-8晶体溶解现象的存在,虽然纳米级晶体的晶种层分布均匀,但晶体外表面积大,在合成过程中晶体溶解速度快,不能很好地起到成核位点的作用,未能得到连续的ZIF-8膜；而对于微米级的晶体,虽然晶种层不及纳米晶体均匀,但是由于外表面积小,在合成过程中溶解速度慢,晶体能够很好地发挥成核位点的作用,在短短的2小时内就诱导形成了连续致密的膜层,膜层厚度仅为7μm, H2渗透速率高达6.07×10-6mol·Pa-1·s-1·m-2,而H2与N2的理想分离因子达到了10.52,远远超过其努森分离因子。在不同的合成时间下研究了纳米晶种以及微米晶种诱导成膜的生长规律,为晶体溶解现象的存在提供证据。对比了不同合成配方中晶体溶解现象的存在情况,证明了含有甲酸钠的合成液中均存在晶体溶解现象。首次采用载体热处理与合成液预晶化相结合的方法,通过原位生长在氧化铝中空纤维管上制备ZIF-8膜。其具体步骤是(1)将氧化铝中空纤维管载体置于150℃的烘箱中加热4.0 h以上；(2)配置摩尔组成为ZnCl2:meIm:HCOONa: CH30H=1:1.5:1:250的合成液,并置于100℃的烘箱中预晶化一定的时间；(3)使合成液冷却后,将热处理过的载体趁热插入预晶化过的合成液中；(4)将合成釜置于100℃烘箱中完成晶化。研究了不同预晶化时间、合成时间以及载体热处理对成膜的影响。结果表明：合成液预晶化1.5 h、合成时间为4.0 h的条件下,制备得到了膜层厚度为6μm的ZIF-8膜,气体透过性能测试结果表明H2的渗透率达到了1.38×10-5mol·Pa-1·s-1·m-2,H2/N2的理想分离因子为5.27,超过其努森分离因子。
[Abstract]:Metal organic frameworks (Metal, Organic Frameworks, MOFs) is a kind of organic inorganic composite porous materials by metal ions and organic ligand, because of its excellent surface area and optical properties and other functions, in recent years has always been a hot research. (Zeolitic Imidazolate zeolite imidazolate frameworks Frameworks, ZIFs) as a an important subclass of MOFs, is composed of transition metal (Zn, In) porous materials and N containing imidazole organic cross-linking to form, its skeleton space mesh topology is similar to zeolite, and has a very large surface area, specific pore structure and excellent thermal stability and chemical stability, so it has very broad application prospects in the research field of membrane materials. At present the research of ZIFs film has experienced a rapid development period, the research on ZIFs film is mainly concentrated however emerge in an endless stream, The composite film in the sheet carrier or dispersed in organic form, need to use complex carrier modification or addition of binder and other means, and the film is generally thick, gas flux is not high, the film performance is restricted, and the sheet carrier is not suitable for making membrane, large-scale industrial application is not for the ZIF-8 film. To solve the above problems, this paper adopts high porosity, large surface area and suitable for alumina hollow fiber on the industrial pipe as the carrier, to study the influencing factors on the preparation of ZIF-8 film on the surface of the alumina. With self-made hollow fiber tube as the carrier, using simple seed dipping coating on the surface of the carrier the seed layer, the two growth were prepared. The ZIF-8 film focuses on seed size, synthesis time, effect of synthetic formula and other factors on the film. The experimental results show that the ZIF-8 crystal The dissolution phenomenon, although the nano crystal seed layer of uniform distribution, but the crystal appearance of large area, in the process of synthesis of crystal dissolution speed, can play very well to the nucleation sites, failed to get a continuous ZIF-8 film; and for micron crystal, although less than the seed layer nano crystal uniform, but because of the appearance of a small area, in the synthesis process, slow dissolution rate, crystal can play well the role of nucleation sites, the film formed by continuous dense in just 2 hours, the film thickness is only 7 m, the permeation rate of H2 is 6.07 * 10-6mol Pa-1. S-1, m-2, and the ideal separation factor H2 and N2 reached 10.52, far more than the Knudsen separation factor under different synthesis. In the study of nanocrystalline and microcrystalline film induced the growth of crystal dissolution phenomenon exists for comparative evidence. The presence of crystal dissolution phenomena of different synthetic formula, proved that the crystal dissolution phenomena are synthetic solution containing sodium formate. Carrier method of heat treatment and pre crystallization combination of synthetic fluid used for the first time, the growth in ZIF-8 film was prepared by in situ alumina hollow fiber tube. The specific steps are (1) oven alumina hollow fiber carrier in 150 DEG C in heating above 4 h; (2) the molar composition of the synthesis solution configuration ZnCl2:meIm:HCOONa: CH30H=1:1.5:1:250, and in the time of 100 DEG C in an oven for a pre crystallization; (3) the synthesis liquid cooled, carrier will heat treated while hot insert pre crystallization synthesis liquid the; (4) the synthesis reactor is put into 100 DEG C oven complete crystallization was studied. Different pre crystallization time, reaction time and the influence of heat treatment on the carrier film. The results show that the synthetic liquid pre crystallization synthesis of 1.5 h. Time is 4 h under the conditions of preparation of the ZIF-8 film thickness is 6 m, gas permeability test results show that the penetration rate of H2 reached 1.38 * 10-5mol - Pa-1 - S-1 - m-2, ideal separation factor of H2/N2 is 5.27, more than the Knudsen separation factor.

【学位授予单位】：浙江大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：TQ051.893

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