铝与氮氧化物高温均相反应机理的量子化学计算研究

为了研究Al粉在氮氧化物中的燃烧特性,采用量子化学密度泛函理论ωB97X方法,研究了Al与3种氮氧化物(NO₂、NO和N₂O)的反应机理。首先,使用ωB97X-D3方法在def2-SVP基组水平上优化了各反应物、中间体、过渡态和产物的几何构型,通过频率分析证实中间体和过渡态的真实性,并通过内禀反应坐标(IRC)计算以进一步确定过渡态,得到了详细反应路径和机理。同时,使用双杂化泛函PWPB95结合DFT-D3校正和def2-TZVPP基组获得了各结构的单点能,并使用变分插值过渡态理论计算了相关反应的反应速率常数,得出每个反应的阿伦尼乌斯表达式。结果表明,Al与NO和NO₂的反应过程为Al与O氧原子连接形成复合物中间体后通过三元环状过渡态破坏N-O键生成产物;Al与N₂O的反应时则为Al与N原子形成复合物后通过四元环状过渡态发生消除反应生成产物。通过分析各反应动力学参数得到Al与NO₂、NO和N₂O反应活化能分别为:4.3,249 kJ·mol^-1<...

Quantum Chemical Caculation Study on the Mechanism of Homo⁃ geneous Chemical Reaction of Aluminum and Nitrogen Oxides at High Temperature

In order to investigate the combustion characteristics of Al powders in NOx， the reaction mechanism of Al with three nitrogen oxides （NO₂， NO and N₂O） was studied by means of density functional theory ωB97X. Firstly， the geometries of reactants， intermediates， transition states and products were optimized with all parameters. The authenticity of intermediates and transition states was confirmed by frequency analysis. The transition states were further determined by intrinsic reaction coordinates （IRC） calculation， and then the detailed reaction paths and mechanisms were obtained. High precision single-point energy of each structure was obtained by using the double hybrid functional PWPB95 combined with DFT-D3 correction and def2-TZVPP basis set. The rate constants of the related reactions were calculated by using the variational interpolation transition state theory， and the Arrhenius expressions for each reaction are obtained. The results show that the reaction process of Al with NO and NO₂ is that Al and O atoms join together to form the intermediate of the complex， and then break the N─O bond through the ternary ring transition state to form the product. When Al reacts with N₂O， Al reacts with N atoms to form a complex and then the elimination reaction takes place through the ring transition states. The activation energies of the reaction of Al with NO₂， NO and N₂O are 4.3 kJ·mol^-1，249 kJ·mol^-1 and 13.4 kJ·mol^-1， respectively. From 2400 K to 4100 K， the reaction rate of Al with NO₂ and N₂O is higher than 106 m³·mol^-1·s^-1， which indicates that the reaction is easy to take place and the reaction rate is very fast， and the reaction rate of Al with NO is about 1/10000 of that of Al with NO₂ and N₂O.