【作者】 白立光；

【导师】 陈标华； 朱吉钦；

【作者基本信息】 北京化工大学 ， 化学工程与技术， 2011， 博士

【摘要】 相变材料是相变储能技术的核心和基础,其性质的好坏决定着能源利用效率的高低。传统的相变材料包括无机物和有机物两类,无机储能材料具有潜热大、导热系数高、相变时体积变化小的优点,但易出现过冷和相分离的现象,导致其蓄热能力大幅度降低,且具有腐蚀性。有机类相变材料几乎没有相分离的缺点、化学性能稳定,但易挥发、易燃烧、导热性能差。所以,研究可以克服二者缺陷的新型相变蓄热材料成为挑战性课题之一。本论文提出离子液体用作相变储能材料,通过量子化学计算分析离子液体分子结构对离子液体性质的影响规律,指导实验合成一系列性能良好的离子液体,并对其热力学性质进行研究,探索离子液体用于跨季节蓄热、工业废热、热泵等领域的可行性。首先对离子液体分子结构和熔化热性质进行了QSPR研究。分别采用PM3半经验算法和密度泛函(DFT)算法对离子液体分子结构进行了结构优化。得到如下量子化学结构参数：阴阳离子液体相互作用能(Ei)、偶极矩(μ)、分子轨道能(ELUMO和EHOMO)、前端离子电荷(Gcation和Canion)、分子体积(Vm)、表面积(S)、最短氢键距离(LH)等。结合熔化热实验数据,建立了针对44种离子液体的六参数模型、30种离子液体的四参数模型、22种咪唑盐类离子液体的五参数模型、10种卤代盐类离子液体的三参数模型和9种卤代咪唑盐离子液体的二参数模型。模型的相关系数均大于0.93,具有很好的内部相关性。对测试集的数据进行了外部验证,模型具有很好的外部预测性。当所选训练集中离子液体的阴离子或阳离子相同,或者属于同一类的衍生物时,模型的相关性和预测性较高。五个QSPR模型中,分子体积这一结构描述符对离子液体的相变热影响最大,是最显著参数。另外,分子量、偶极矩和最低分子未占轨道能等描述符对离子液体的熔化热影响也较大。通过对优化结果分析,得到了烷基侧链长度、甲基取代C2位H原子和阴离子变化对离子液体热力学性质的影响规律,用于指导离子液体的合成。通过增加烷基侧链长度、采用甲基取代C2位H原子和选取体积较小的卤族元素阴离子(如,Cl-和Br-)等方式,设计并制备了8种烷基咪唑卤代盐类离子液体和6种己内酰胺类离子液体。分别对上述两种离子液体的热力学性质进行了表征。表征结果表明[C16MIM]Br和口[C16MMIM]Br两种离子液体的相变热最高,分别为144.37J·g-1和123.68J·g-1。两种离子液体固态时的热容高于1.25J·g-1·℃-1,并且随着温度的升高而升高,液态时达到2.3J·g-1·℃-1左右,说明具有很好的显热存储能力。TG表征测得两种离子液体的初始分解温度分别为230℃和250℃,都具有较高的热稳定性。两种离子液体在10-50℃之间的的导热系数介于0.15～0.35W·m-1·℃-1之间。和商业用Therminol(?)VP-1导热流体相比,具有明显的优势。内酰胺类离子液体的熔点温度范围在60～75℃之间,相变潜热在120J·g-1以上,表现出良好的相变储热性能；它们的热容在固态和液态时分别在1.33J·g-1·℃-1和2J·g-1·℃-1以上,表现出良好的显热存储性能。利用离子液体过冷的性质,用于跨季节蓄热。离子液体以液体的形式存储热量,温度降至凝固点以下时,通过加入成核引发剂,激发其发生相变释放出热量。本文选取[C16MIM]Br和[C16MMIM]Br两种离子液体,添加质量比为0～25wt%的铜粉、石墨粉和十八醇作为成核引发剂,考察成核剂对离子液体升降温过程热力学性质的影响。结果表明,[C16MIM]Br+铜粉混合物体系具有合适的温度和稳定的过冷状态,可以用于跨季节蓄热系统。为解决离子液体相变材料相变体积变化、使用过程中的损失及与其周围环境界面的结合等问题,考虑将离子液体包裹进微胶囊。选取三聚氰胺-甲醛(MF)树脂为壁材,[C4MIM]PF6或[C16MIM]PF6为芯材,制备离子液体微胶囊材料。考察了制备工艺和壳材中三聚氰胺/甲醛摩尔配比的影响。当选择一步法制备工艺,三聚氰胺/甲醛配比为1：4.16时,成功制备了包裹[C4MIM]PF6离子液体的相变微胶囊材料。更多还原

【Abstract】 The base and core of phase change energy storage technology is Phase Change Materials (PCMs), of which the quality determines the level of energy efficiency. PCMs, mainly indicating solid-liquid PCMs, include inorganic PCMs and organic PCMs. Inorganic PCMs possess high fusion heat, high thermal conductivity and small volume change. While they are prone to get supercooling and phase separation, which can decrease their thermal storage capacity severely. At the same time inorganic PCMs are usually corrosive. Organic PCMs have not the disadvantage of phase separation and are stable. While organic PCMs are highly volatile and flammable, this represents a considerable safety concern for many applications. Also their thermal conductivities are generally low. Therefore new PCMs overcoming the defects of inorganic and organic PCMs are urgently needed. In this work, ionic liquids (ILs) were supposed to be used as PCMs. Quantum chemistry calculation methods were used to recognize the structure effects of ionic liquids to their properties and used for directing the experimental preparation of novel ionic liquids with good performances. Thermodynamic properties of the synthesized ILs were characterized, and their applications in seasonal heat storage, industrial waste heat, and heat pump were investigated.QSPR methods were firstly adopted to study the relationship between structures and heat of fusion of ionic liquids. The geometries of ILs were optimized by PM3semi-empirical calculation and Density Function Theory (DFT) separately. Then, Quantum chemistry parameters were obtained from the output file:cation-anion interaction energy (Ei), Dipole moment (μ), energy molecular orbital (ELUMO and EHOMO), electric charge of front atom (Ccation and Canion), molecular volum (Vm), surface area (S) and shortest hydrogen bond distance (LH).6-parameters model for44ILs,4-parameters model for30ILs,5-parameters model for22imidazolium ILs,3-parameters model for10halide ILs and2-parameters model for9halide imidazolium ILs were constructed. The correlation coefficients were greater than0.93which showed satisfactory internal consistency. The predictabilities of QSPR models were evaluated by external datasets. It was concluded that the validity of the correlation models were greatly depending on the consistency of cation and anion structures of ILs. Besides, the most effective descriptor for heat of fusion was molecular volume. The other descriptors, such as MW,μ and ELUMO, were also important factors. The influencing rules of alkyl side chain length, methyl substitution at C2, and variations of anion on the thermodynamic properties of ILs were obtained and were used for directing the preparation of ILs. Eight kinds of imidazolium halide ILs and six kinds of caprolactam ILs were prepared by changing the length of alkyl side chain, methyl substitution at C2, and selecting small volum anion (ie, Cl-and Br-).Thermodynamic properties of ILs prepared in this work were characterized. The results indicated that the heat of fusion of [C16MIM]Br and [C16MMIM]Br were144.37J·g-1and123.68J·g-1, respectively.[C16MIM]Br and [C16MMIM]Br performed good sensible heat storage. The heat capacities of two ILs at solid state were higher than1.25J·g-1·℃-1and increased with increasing temperature. The heat capacities of two ILs at liquid state were about2.3J·g-1·℃-1. The initial decomposition temperatures for two ILs are230℃and250℃. When temperature ranges from10℃to50℃, thermal conductivities of imidazolium ILs are between0.15～0.35W·m-1·℃-1which are higher than that of Therminol(?) VP-1heat transfer fluid.Melting points, heat of fusions and heat capacities6kinds of caprolactam halide ILs were characterized. They performed comparatively good latent heat and sensitive heat storage properties. The thermodynamic properties of caprolactam halide ILs are below:melting points are in the range of60～75℃, heat of fusions are above120J·g-1, heat capacities at solid state and liquid state are above1.33J·g-1·℃-1and2.0J·g-1℃, respectively.The active use of supercooling of ionic liquids for seasonal solar energy storage was proposed, which means that the thermal energy is stored in a supercooled liquid state and released by nucleating agents when needed.[C16MIM]Br and [C16MMIM]Br are selected in this work, copper powder, graphite powder and1-octadecanol as nucleating agents are added with different mass ratios (0-25wt%) and their effects on the thermodynamic properties of two ionic liquids are investigated. The result indicates that the [C16MIM]Br+copper powder behaves proper melting points and stable supercooling state that are more suitable for seasonal thermal energy storage.In order to solve the problems of IL-PCMs, such as the volume changes during phase change, loss during the using process and combination with the surroundings, ILs were supposed to be packaged into microcapsule. Using melamine-formaldehyde resin (MF) as wall materials and [C4MIM]PF6or [C16MIM]PF6as inner materials, the microencapsulated ILs were prepared. The effects of preparation method and the molar ratio of melamine/formaldehyde were studied. The microencapsulated [C4MIM]PF6were successfully prepared by one step method when the molar ratio of melamine/formaldehyde was1:4.16.更多还原