金属—有机骨架材料气相分离性能的分子模拟研究

发布时间：2018-03-19 14:28

本文选题：金属-有机骨架材料　切入点：离子液体　出处：《北京化工大学》2016年博士论文　论文类型：学位论文

【摘要】：近十年来,由无机金属簇与有机配体通过配位键构筑而成的金属-有机骨架材料(Metal-Organic Frameworks, MOFs)是纳微结构新材料领域研究的热点之一。MOF材料具有比表面积和孔隙率高、种类多样、功能性强和孔道可设计性强等特点,在能源气体储存、气/液相吸附分离、膜分离、催化、传感和药物控释等领域表现出了良好的应用前景。目前已合成的MOF材料超过两万种,单纯的实验测试方法不能满足MOF材料快速发展的需求。计算化学,作为实验测试方法的有效辅助手段,在获得微观机理、探索新现象、构建结构-性能关系、快速筛选材料和新材料搭建及设计等方面具有极大的优势。计算化学方法与实验测试方法相结合,大大促进了MOF材料的进步与发展。本工作中,采用分子模拟方法对MOF材料和离子液体/MOF复合物在气相吸附分离和膜分离方面的性能进行了系统研究,主要工作内容如下：1、针对151种不同类型的MOF材料,采用分子模拟手段,系统地研究了变温吸附(Temperature Swing Adsorption,TSA)过程中材料对CO_2/CH4混合体系的吸附分离性能。本工作率先将脱附能耗引入到材料工业应用评价标准中,并与常见的评价标准相结合,对材料的吸附分离性能进行了全面评价。通过构建材料对CO_2/CH4混合体系分离性能的构效关系,发现,吸附度差与材料的脱附能耗、吸附选择性、CO：工作容量和再生率之间存在良好的关联性,但是变化趋势不同。在一定范围内,吸附度差可以作为材料快速筛选和高性能材料设计的标准。同时,筛选出了分离性能优异的MOF材料,分析了其结构特点,给出了设计高性能材料的依据和策略。2、针对天然气中痕量H2S的脱除过程,采用分子模拟方法,研究了离子液体(Ionic Liquds, ILs)在Cu-TDPAT孔道内的分布规律和IL/Cu-TDPAT复合物对H2S/CH4混合体系的分离性能。本工作中选择了四种阳离子相同而阴离不同的离子液体与Cu-TDPAT进行复合。研究结果表明,离子液体中阴离子体积的大小和添加量会影响其在孔道内的填充过程,进而影响材料对H2S/CH4混合体系的分离性能。添加离子液体提高了材料与H2S之间的相互作用力,且相比于Cu-TDPAT材料,IL/Cu-TDPAT复合物对H2S/CH4的分离选择性有了明显提高。其中,IL的添加量为25 IL分子/晶胞时,[BMIM][Cl]/Cu-TDPAT复合物的H2S/CH4的分离选择性在1 bar和10 bar时分别达到了1302和715,远远超过了目前已报道的材料。此外,结合工业实际中的变压吸附和真空吸附工艺,发现,添加离子液体在提高材料吸附选择性的同时还可以提高材料对H2S的工作容量。上述结果表明,向MOF材料孔道内添加离子液体是一种可以快速提高材料对H2S/CH4混合体系分离性能的策略。3、提出了向MOF材料中加入离子液体,在材料中形成新的狭窄扩散通道的“空穴占据”策略,以提高MOF材料的膜分离性能。针对结构稳定的ZIF-8材料,采用分子模拟方法,通过添加离子液体对其孔道进行修饰,研究了离子液体对材料的CO_2/N_2吸附分离性能和膜分离性能的影响,并进一步研究了IL/ZIF-8复合物与聚合物膜形成的混合基质膜的分离性能。结果表明,加入离子液体提高了材料对CO_2/N_2混合体系的吸附选择性；作为膜材料,IL/ZIF-8复合物表现出了较高的渗透选择性和CO_2渗透率,跨过了Robeson制约关系,且其膜分离选择性高于常见的MOF材料。对具有中等渗透选择性和CO：渗透通量的聚合物膜来说,添加IL/ZIF-8复合物可以同时提高聚合物膜的渗透选择性和CO_2渗透通量。上述结果说明,向MOF材料孔道内添加离子液体进行孔道调控和修饰是一种有效地获得高分离性能吸附剂和膜材料的策略。4、因烟道气中含有H2O和SO_2等微量杂质,故采用分子模拟方法探究了H2O和SO_2分子对IL/UiO-66复合物的CO_2/N_2分离性能的影响规律。结果表明,添加离子液体后,材料的CO_2/N_2分离性能有了大幅提高且离子液体添加越多,材料的选择性越高。在湿润环境中,H2O与CO_2分子在材料内部存在竞争吸附,而H2O分子又会提供CO_2吸附位,增强材料对CO_2分子的相互作用,两种效应共同作用影响材料的分离选择性。在[BMIM][Cl]/UiO-66和[BMIM][PF6]/UiO-66复合物中,竞争吸附作用明显,使得材料选择性下降。因SO_2含量很少,其存在对UiO-66的CO_2/N_2分离选择性影响不大。在IL/UiO-66复合物中,随着SO_2含量的上升,增强了被吸附分子之间的相互作用,进而提高了复合物的CO_2/N_2分离选择性。
[Abstract]:In the past ten years, from inorganic metal clusters and organic ligands through coordination bonds form metal organic frameworks (Metal-Organic, Frameworks, MOFs) is one of the hot spots of.MOF nano micro structure research field of new materials with specific surface area and high porosity, species diversity, functional characteristics and design of channel can be so, the energy stored in the gas, gas / liquid adsorption separation, membrane separation, catalysis, sensing and drug control field has a good application prospect. At present more than twenty thousand kinds of MOF materials have been synthesized, experimental testing method alone can not meet the rapid development of MOF material demand. Computational chemistry, as an effective the auxiliary means of experimental testing method, in micro mechanism, explore new phenomena, construct the relationship between structure and properties, has great advantages to build a rapid screening materials and new materials and design. The calculation and real chemical method Test method of combining, greatly promoted the progress and development of MOF materials. In this work, using molecular simulation methods on the properties of MOF materials and ionic liquid /MOF complexes in the gas phase adsorption and membrane separation were studied. The main contents are as follows: 1, according to the 151 different types of MOF the material, by means of molecular simulation, studied the temperature swing adsorption (Temperature Swing, Adsorption, TSA) adsorption and separation performance of CO_2/CH4 hybrid system in the process of material. This work will be the first desorption energy consumption into the industrial application of materials evaluation criteria, and combined with the common evaluation criteria, comprehensive evaluation of adsorption and separation the properties of the material. By constructing the structure-activity relationship, the separation performance of CO_2/CH4 hybrid material system, adsorption desorption degree difference of material consumption, selective adsorption capacity and regeneration work: CO There is good correlation between the rate of change, but the trend is different. In a certain range, the adsorption degree difference can be used as materials for rapid screening standards and design of high performance materials. At the same time, selected MOF material with excellent separation performance, analyzes its structure characteristics, gives the basis and strategy for the design of high performance materials.2. For the removal of trace H2S in natural gas, using molecular simulation method, studied the ionic liquids (Ionic Liquds, ILs) distribution and separation properties of IL/Cu-TDPAT complexes in the Cu-TDPAT channel of H2S/CH4 hybrid system. This work chose four kinds of Cation Anion same and different ionic liquids with Cu-TDPAT composite. The results show that the volume of the anion in ionic liquids and the size of amount will affect the filling in the pores, thereby affecting the material on the separation performance of H2S/CH4 mixture Tim. With the increase of ionic liquid interaction between materials and H2S, and compared to the Cu-TDPAT material, the separation selectivity of IL/Cu-TDPAT complex on H2S/CH4 has been significantly improved. Among them, the content of IL was 25 IL molecules / cell, [BMIM][Cl]/Cu-TDPAT complexes of H2S/CH4 separation selectivity at 1 bar and 10 bar respectively. 1302 and 715, far more than the reported materials. In addition, it was found that the combination of vacuum pressure swing adsorption and adsorption process in industrial practice, adding ionic liquid in improving the adsorption selectivity can also improve the working capacity of H2S material. The results show that adding ionic liquid to material pore is MOF one can quickly improve the material strategy.3 on the separation performance of the hybrid H2S/CH4 system, put forward the ionic liquid is added to the MOF material, forming a narrow diffusion channel new "holes in the material Take "strategy to improve the MOF membrane separation performance. According to the structural stability of ZIF-8 materials by molecular simulation method, by adding ionic liquid is used to modify the pore, the effects of CO_2/N_2 adsorption and membrane separation performance of ionic liquid material, the separation performance of mixed matrix membranes and further study of the IL/ZIF-8 composite with the formation of the polymer film. The results show that the ionic liquid is added to improve the adsorption selectivity for CO_2/N_2 mixtures; as membrane material, IL/ZIF-8 composites showed higher permeation selectivity and CO_2 permeability across the Robeson restricted, and its membrane separation selectivity is higher than that of common MOF of materials. The middle permeable selectivity and CO polymer membrane, adding IL/ZIF-8 compound can improve the polymer membrane selectivity and permeability CO_2 The flux. The results showed that adding ionic liquid to MOF material pore channel regulation and modification is an effective way to obtain high separation performance of the adsorbent and membrane materials for policy.4, containing H2O and SO_2 trace impurities such as flue gas, the influence of molecular on separation performance of H2O and SO_2 molecules CO_2/N_2 the IL/UiO-66 complex simulation method. The results showed that adding ionic liquid, CO_2/N_2 separation properties of materials has been greatly improved and the ionic liquid added more material selectivity is higher. In the wet environment, H2O and CO_2 into the competitive adsorption existed inside the material, but also will provide CO_2 H2O molecular adsorption, enhance interaction materials of CO_2 molecules, the interaction between the two effects of selective separation material. In the [BMIM][Cl]/UiO-66 and [BMIM][PF6]/UiO-66 complexes, the competitive adsorption significantly, making the The selectivity of materials decreases. Because the SO_2 content is very small, its existence has little effect on the selectivity of UiO-66 CO_2/N_2 separation. In the IL/UiO-66 complex, with the increase of SO_2 content, the interaction between the adsorbed molecules is enhanced, and the CO_2/N_2 separation selectivity of the composite is enhanced.

【学位授予单位】：北京化工大学
【学位级别】：博士
【学位授予年份】：2016
【分类号】：O641.4;TQ028

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