胺类二氧化碳吸收剂的结构及性质研究

发布时间：2018-06-24 10:14

本文选题：碳捕集 + 多元胺　；参考：《北京化工大学》2015年博士论文

【摘要】：胺水溶液法是目前最有效、可行的大规模CO2捕集方法之一。为实现对烟道气中CO2的吸收分离,需要探求吸收能力高、能耗低的胺类吸收剂。本文从实验和理论两方面研究了吸收剂分子结构与吸收性能之间的构效关系。实验测定了吸收剂的CO2溶解度、酸碱度、混合热等热力学性质,并进行了相关的热力学模拟。理论研究方面,结合统计力学积分方程理论与密度泛函理论,对胺-水、胺-CO2及胺-N2O相互作用开展研究。主要工作包括：(1)测量了不同结构多元胺中CO2的溶解度及胺与水的混合热,确定了分子结构与CO2溶解度及混合热之间的对应关系；利用溶解度数据估算出胺与CO2的反应热,分析了吸收剂分子内不同官能团对反应热的影响；综合考虑CO2溶解度、混合热与反应热等热力学性质、吸收剂的物性及价格,筛选出了两种具有潜力的碳捕集吸收剂：二乙烯三胺与3,3'-二氨基二丙基胺,并采用酸碱滴定法测定了其酸解离常数(pKa)。(2)为得到高吸收量、低腐蚀与低能耗的吸收剂,在筛选出胺中添加了N-甲基二乙醇胺与二甘醇使其形成混合吸收剂,得到{二乙烯三胺+N-甲基二乙醇胺+水}及{二乙烯三胺+N-甲基二乙醇胺+二甘醇+水}两类混合吸收剂,测定了两种混合吸收剂在不同浓度时的CO2溶解度。结果表明：二乙烯三胺混合吸收剂不但提高了溶解度,降低了反应热,而且减小了由挥发导致的溶剂损失,降低了对设备的腐蚀性。二乙烯三胺与N-甲基二乙醇胺为3：7(摩尔比)时,综合性能最佳。(3)基于密度泛函理论构建了采用自由能泛函表述的桥函数,并将其应用到积分方程的三维参考作用点(3D-RISM)模型中进行能量校正,提高3D-RISM的自洽性,定量表征了H2O、CO2及N20在不同胺分子周围的三维密度分布,确定了胺分子中不同官能团对溶剂化效应及对C02密度分布的影响,从分子层面解释了溶剂化效应及构效关系。根据胺分子周围H2O、CO2及N20的密度分布,计算得到了胺分子的溶剂化自由能及Henry系数,计算结果与实验值基本吻合,表明该模型对胺吸收剂-C02相互作用而形成的空间结构描述是可靠的,为设计新型高效的吸收剂、改善吸收过程中的热力学与动力学性能提供了理论依据。(4)以非随机双流体电解质(e-NRTL)模型为基础,构建胺与C02反应体系的热力学模型,利用热容、混合热、汽液平衡、饱和蒸汽压以及CO2溶解度,通过e-NRTL模型获得了DETA、DETA-H2O、DETA-H2O-CO2及DETA-MDEA-H2O-CO2等体系的相关热力学参数,并计算了混合胺体系的CO2溶解度,模型计算值与实验值基本吻合,表明该模型可用于计算工业碳捕集过程中相关体系的汽液平衡、混合热、溶解度,为工艺流程设计提供重要的基础参数。
[Abstract]:Amine aqueous solution method is one of the most effective and feasible methods for CO 2 capture. In order to achieve the absorption and separation of CO2 in flue gas, the amine absorbent with high absorbability and low energy consumption is needed. In this paper, the structure-activity relationship between the molecular structure of absorbent and its absorption properties is studied from both experimental and theoretical aspects. The thermodynamic properties of CO _ 2 solubility, pH and mixing heat of absorbent were measured and the thermodynamic simulation was carried out. In terms of theoretical study, the interaction of amine-water, amine-CO2 and amine-N2O is studied in combination with the theory of statistical mechanical integral equation and density functional theory. The main works are as follows: (1) the solubility of CO _ 2 in polyamines with different structures and the heat of mixing between amine and water are measured, the corresponding relationship between molecular structure and solubility of CO _ 2 and heat of mixing is determined, and the heat of reaction between amine and CO _ 2 is estimated by solubility data. The influence of different functional groups in absorber on the reaction heat was analyzed, the thermodynamic properties of CO2 solubility, mixing heat and reaction heat, the physical properties and the price of absorbent were considered synthetically. Two potential carbon-trapping absorbents, diethylenetriamine and 3Aminodipropylamine, were screened out, and their acid dissociation constants (PKA). (2) were determined by acid-base titration to obtain high absorbency, low corrosion and low energy consumption. N- methyl diethanolamine and diethylene glycol were added to the screened amine to form a mixed absorbent. Two kinds of mixed absorbers {diethylenetriamine N-methyldiethanolamine water} and {diethyltriamine N-methyldiethanolamine diethylene glycol water} were obtained. The results show that the mixture of diethylenetriamine absorbent not only improves the solubility, reduces the reaction heat, but also reduces the solvent loss caused by volatilization and the corrosion to the equipment. When the molar ratio of diethylenetriamine and N-methyldiethanolamine is 3:7 (molar ratio), the comprehensive performance is the best. (3) based on density functional theory, a bridge function expressed by free energy functional is constructed. It is applied to the three-dimensional reference point model of the integral equation (3D-RISM) for energy correction, which improves the self-consistency of 3D-RISM, and quantitatively characterizes the three-dimensional density distribution of H _ 2O _ 2 and N _ (20) around different amine molecules. The effects of different functional groups on the solvation effect and the density distribution of CO2 were determined. The solvation effect and structure-activity relationship were explained at the molecular level. According to the density distribution of H _ 2O _ 2 and N _ (20) around amine molecule, the solvation free energy and Henry's coefficient of amine molecule are calculated. The calculated results are in good agreement with the experimental values. It is shown that the model is reliable for describing the spatial structure of the interaction of amine absorbent C02, and is used to design new and efficient absorbent. The thermodynamic and kinetic properties of the absorption process are improved. (4) based on the non-random two-fluid electrolyte (e-NRTL) model, the thermodynamic model of the reaction system of amine and CO2 is constructed, using heat capacity, mixing heat, vapor-liquid equilibrium. The thermodynamic parameters of DETA-DETA-H2O-DETA-H2O-CO _ 2 and DETA-MDEA-H2O-CO _ 2 were obtained by e-NRTL model, and the solubility of CO _ 2 in mixed amine system was calculated. The calculated values of the model were in good agreement with the experimental values. It is shown that the model can be used to calculate the vapor-liquid equilibrium, mixing heat and solubility of the relevant systems in the process of industrial carbon capture, which provides important basic parameters for the process design.
【学位授予单位】：北京化工大学
【学位级别】：博士
【学位授予年份】：2015
【分类号】：X701;TQ028.17

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