【作者】 曾秀琳；

【导师】 刘家骢； 陈网桦；

【作者基本信息】 南京理工大学 ， 工程力学， 2007， 博士

【摘要】 本论文以量子化学理论方法和实验方法，对硝酸正丙酯（NPN）、硝酸异丙酯（IPN）、硝酸异辛酯（EHN）、二缩三乙二醇二硝酸酯（Tri-EGDN）和三缩四乙二醇二硝酸酯（Tetra-EGDN）的热安定性进行了综合分析研究。用从头计算（ab initio）、密度泛函理论（DFT）和半经验分子轨道（MO）等方法研究了五种硝酸酯和对应自由基的平衡几何构型、电子结构、IR光谱、生成热等其它热力学性质和热分解机理。利用常压DSC、高压DSC、加速量热仪（ARC）对硝酸酯的热分解性能进行了研究。主要内容如下：使用DFT-（U）B3P86/6-31+G^*方法，优化计算五种硝酸酯和对应自由基的平衡几何构型，分析了几何参数在硝酸酯分子和自由基中的变化规律。在优化的基础上，分析了硝酸酯和自由基的电子结构，如电荷分布、Mulliken布居、前线轨道能(E_HOMO、E_LUMO)、前线轨道能级差(△E=E_LUMO-E_EHOMO)和偶极矩。运用DFT-B3LYP方法，在6-31G^*基组水平下，计算了五种硝酸酯和对应自由基的IR频率和298～800K温度范围的热力学性质(H°_m、C°_p，m和S°_m)。分别使用HF、B3LYP和B3P86方法，结合6-31G^*和6-31+G^*基组，经等键反应设计；半经验方法（AM1、MINDO/3和PM3）；基团加和法和键能加和．法计算了五种硝酸酯的生成热，通过与可得的实验数据比较可知，由B3P86/6-31G^*方法，通过等键反应计算得到物质的生成热最接近真实值，所以NPN、IPN、EHN、Tri-EGDN和Tetra-EGDN可取的标准生成热分别是-169.52kJ·mol^-1、-184.08 kJ·mol^-1、-240.36 kJ·mol（-1）、-576.88 kJ·mol^-1和-793.91 kJ·mol（-1）.分别在B3LYP/6-31G^*、B3LYP/6-31+G^*、B3P86/6-31G^*、B3P86/6-31+G^*、HF/6-31G^*、HF/6-31+G^*的水平下，根据热化学理论和Morokuma方法，计算得到五种硝酸酯的O-NO₂键离解能（BDE）。阐明了五种物质的热分解机理。采用常压DSC和高压DSC实验方法研究了NPN、IPN、EHN和Tri-EGDN的热分解特性，获得了热分解反应动力学参数。研究结果表明，常压下四种硝酸酯的热分解反应发生在气相区，当压力增大到2MPa时，四种物质直接发生了液相分解反应，并且分解放热峰的峰温后移。使用加速量热仪研究了NPN、IPN和EHN的热安定性。得到了热分解温度随时间的变化曲线、自放热速率随温度的变化曲线、分解压力随温度的变化曲线以及分解压力随升温速率的变化曲线，分析了在绝热条件下热分解反应动力学和热分解过程，计算了表观活化能、指前因子和反应热等参数。由NPN、IPN和EHN的O-NO₂键离解能在很大程度上符合由加速量热仪测试得到的活化能，推知三种硝酸酯的热分解反应只是单分子O-NO₂键的均裂反应。根据NPN、IPN和EHN热分解的起始温度和反应热数据，给出了三种物质在反应危险度等级中的分类，由三种硝酸酯在75℃时的反应风险指针，分析得到三种物质的热失稳风险度。更多还原

【Abstract】 In this paper, both quantum chemical calculations and experimental methodshave been comprehensively carried out on thermal stability of five nitrates: n-propylnitrate （NPN）, isopropyl nitrate （IPN）, 2-ethylhexyl nitrate （EHN）, tri-ethyleneglycol dinitrate （Tri-EGDN）, and tetraethylene glycol dinitrate （Tetra-TEGDN）. Thequantum chemical methods such as ab initio, density functional theory （DFT） andseveral semiempirical MO methods were employed to study them and theircorresponding radicals’ equilibrium geometries, electronic structures, infraredvibrational spectra, heats of formation and the other thermodynamic properties,pyrolysis mechanism. Thermal decomposition properties of some nitrates were alsoinvestigated with Ambient-Pressure DSC, High-Pressure DSC, and AcceleratingRate Calorimetry （ARC）. The main contents were as follows:The DFT-（U） B3P86/6-31+G^* method was employed to investigate theequilibrium geometries of five nitrates and their corresponding radicals. Thevariational rules of geometrical parameters in molecules and radicals were analyzed.Based on the optimized equilibrium geometry, the electronic structures such ascharge distribution, Mulliken population, frontier orbital energy (E_HOMO, E_LUMO) andenergy gap (△E=E_LUMO-E_HOMO) as well as dipole moments were also analyzed.The IR frequencies, and thermodynamic properties (H°_m, C°_{p, m} and S°_m) in thetemperature range 298～800 K were calculated for five nitrates and theircorresponding radicals, using the DFT method at the B3LYP/6-31 G^* level.The heats of formation （HOFs） were calculated for five nitrates by usingHartree-Fock and Density Functional Theory （B3LYP and B3P86 methods）, with6-31 G^* and 6-31+G^* basis sets via isodesmic reactions, semiempirical MO methodsas well as two additivity schemes. Compared with experimental values available,HOFs from B3P86/6-31 G^* level can be referred to as criteria for five nitrates. On thebasis of our calculations, we recommend HOF values for NPN, IPN, EHN,Tri-EGDN and Tetra-EGDN, are-169.52 kJ·mol^-1, -184.08 kJ·mol^-1, -240.36kJ·mol^-1, -576.88 kJ·mol^-1 and -793.91 kJ·morl^-1, respectively.Under B3LYP/6-31G^*, B3LYP/6-31+G^*, B3P86/6-31G^*, B3P86/6-31+G^*,HF/6-31G^*, and HF/6-31+G^* levels, the bond dissociation energies （BDEs） of O-NO₂ bond in five nitrates were calculated by using the thermo-chemical schemesupplied by Gaussian and Morokuma methods. The pyrolysis mechanism of five titlecompounds is also elucidated.The thermal decomposition characteristics of NPN, IPN, EHN, and Tri-EGDNwere investigated by means of Ambient-Pressure DSC and High-Pressure DSC.Kinetic parameters of thermal decomposition were obtained. The results show thatthe thermal decomposition process of four nitrates under Ambient-Pressure wasoccurred in gas phase. When the pressure increased up to 2MPa, their decompositionprocess was occurred in liquid phase, and the peak temperature of exothermicdecomposition process increased.The thermal stabilities of NPN, IPN, and EHN were investigated using anadiabatic calorimeter called ARC （Accelerating Rate Calorimetry）. The curves ofthermal decomposition temperature versus time, self-heating rate versus temperature,pressure versus temperature, and pressure versus self-heating rate were obtained.The thermolysis kinetics and decomposition process under adiabatic condition wereanalyzed, and kinetics parameters such as apparent activation energy,pre-exponential factor and reaction heat were calculated.From the finding that the calculated results of O-NO₂ BDEs in NPN, IPN, andEHN are well coincident with the experimental results of apparent activationenergies from ARC,. we can draw a conclusion that the experimental thermolysis ofthree nitrates is only unimolecular homolytical cleavage of the O-NO₂ bonds.According to the onset temperature (T_onset) and heat of reaction （—△H） of NPN,IPN, and EHN, their levels in hazard classification for thermal reactivity wereobtained. Based on the reactivity risk index （RRI） at 75℃of three nitrates, theirthermal instability were also gained.更多还原