N-烷基吡啶型离子液体的热力学性质研究

发布时间：2018-06-18 12:09

本文选题：吡啶基离子液体 + 密度　；参考：《辽宁大学》2017年硕士论文

【摘要】：离子液体凭借自身独特的优良性能,诸如饱和蒸气压低,液态温度范围宽以及功能可设计性等,不仅在化学化工研究领域是环境友好的绿色溶剂、高效催化剂和萃取剂,而且在医学领域中药物增溶方面也有广泛的的用途,此外,作为电解质在电池体系中的应用也有所突破。可见,离子液体作为一种潜在的新兴产业,已经在人们与日俱增的需求和日新月异的生产中显示出了卓越的潜在价值,旨在绿色发展、可再生能源的难题上迎接新的机遇和更大的挑战。本文采用中和法设计并合成两类吡啶基离子液体:N-烷基吡啶醋酸型离子液体[CnPy][OAc](n=2-6)和N-烷基吡啶三氟乙酸型离子液体[CnPy][TFA](n=2-6),共十种离子液体,以核磁共振氢谱(1H NMR)、差示量热扫描(DSC)对其进行表征。由于这两类离子液体中阴离子CH3COO-和CF3COO-与极性溶剂水易形成氢键且利用常规方法难以除去,因此在本文的热力学性质测定中,均采用标准加入法(SAM)来消除杂质水的干扰,线性拟合之后经过外推得到纯离子液体的各项性质数据。在(293.15-343.15)±0.1 K温度范围内,每隔5 K测定了不同含水量的这两类离子液体的密度、表面张力和折光率。在此实验数据基础上,利用半经验方法估算了这两类离子液体的体积性质和表面性质。首先,计算了离子液体的分子体积并考察了分子体积随温度和烷基链中碳原子数的变化情况;根据Glasser理论得到标准熵(298)和晶格能的数值,并分析了标准熵随烷基链中碳原子数的线性变化情况,得到了每个亚甲基对标准熵的贡献值;通过比较离子液体与无机熔融盐的晶格能的大小,解释了离子液体被称为室温熔融盐的原因;此外,计算了离子液体的表面熵和表面能,发现离子液体的表面能相较无机熔融盐是很小的,解释了离子液体在室温仍能保持液体状态的原因。以Kabo和Rebelo的经验方程分别计算了离子液体的汽化焓并分析了导致结果存在差异的可能性。利用摩尔表面Gibbs自由能的概念对传统的E?tv?s方程进行改进,在所得的修正E?tv?s方程中,其斜率和截距都有明确的含义,分别代表摩尔表面熵和摩尔表面焓。结合摩尔表面Gibbs自由能和折光率对这两类离子液体的表面张力进行估算,结果与相应的实验值吻合。根据空隙理论计算所得的两类离子液体的热膨胀系数,在数量级上与相应的实验值一致。经过对空隙理论的延伸,本文提出空隙摩尔表面Gibbs自由能的概念,通过推导发现其值是一个与离子液体的种类无关的常量。最后,利用液体的溶解性参数这一新标度对两类离子液体的极性进行了估算,用极性大小判断其亲、疏水性,结果与我们的日常经验判断相一致。
[Abstract]:Ionic liquids are not only environmentally friendly green solvents, efficient catalysts and extractants, but also have excellent properties such as low saturated vapor, wide range of liquid temperature and functional designability. In addition, the application of electrolyte in battery system is also breakthrough. It can be seen that ionic liquids, as a potential emerging industry, have shown remarkable potential value in increasing demand and rapid production, aiming at green development. Renewable energy challenges to meet new opportunities and greater challenges. In this paper, two kinds of pyridyl ionic liquids, [CnPy] [OAC] (CnPy) and [CnPy] [TFA] [CnPy] [TFA], have been designed and synthesized by neutralization method. It was characterized by 1H NMR and differential scanning calorimetry (DSCS). Since the anions CH3COO- and CF3COO- in these two kinds of ionic liquids are easy to form hydrogen bonds with polar solvent water and are difficult to be removed by conventional methods, the standard addition method (SAM) is used to eliminate the interference of impurity water in the determination of thermodynamic properties of these two kinds of ionic liquids. After linear fitting, the properties of pure ionic liquids were extrapolated. In the temperature range of 293.15-343.15) 卤0.1 K, the density, surface tension and refractive index of the two kinds of ionic liquids with different water content were measured every 5 K. Based on the experimental data, the volume and surface properties of the two kinds of ionic liquids were estimated by semi-empirical method. Firstly, the molecular volume of ionic liquids is calculated and the variation of molecular volume with temperature and the number of carbon atoms in alkyl chain is investigated. The linear variation of standard entropy with the number of carbon atoms in alkyl chain is analyzed, the contribution of each methylene to standard entropy is obtained, and the lattice energy of ionic liquid and inorganic molten salt is compared. The reason why ionic liquids are called room temperature molten salts is explained. In addition, the surface entropy and surface energy of ionic liquids are calculated. It is found that the surface energy of ionic liquids is smaller than that of inorganic molten salts. The reason why ionic liquids can remain liquid at room temperature is explained. The enthalpy of vaporization of ionic liquids was calculated by the empirical equations of Kabo and Rebelo and the possibility of difference in the results was analyzed. By using the concept of Gibbs free energy of molar surface, the traditional Etvsof equation is improved. The slope and intercept have clear meanings in the modified Etotvs equation, which represent the molar surface entropy and the molar surface enthalpy, respectively. The surface tension of these two kinds of ionic liquids is estimated by combining the Gibbs free energy and refractive index of the two kinds of ionic liquids, and the results are in agreement with the corresponding experimental values. The thermal expansion coefficients of the two kinds of ionic liquids calculated according to the void theory are in agreement with the corresponding experimental values in the order of magnitude. Through the extension of the void theory, the concept of Gibbs free energy on the void molar surface is proposed in this paper. It is found that its value is a constant independent of the species of ionic liquids. Finally, the polarity of two kinds of ionic liquids is estimated by using the new scale of solubility parameter of liquid. The hydrophobicity and hydrophobicity of the two kinds of ionic liquids are judged by the size of polarity. The results are in agreement with our daily experience.
【学位授予单位】：辽宁大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：O645.1

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