碳烟成核过程中萘到菲的生长路径研究

由于火焰中多环芳香烃(PAHs)的实验浓度与模拟浓度有较大差别,高温环境下PAHs的形成过程一直是研究热点.本文利用量化M06-2X方法和6-311++G(d,p)基组,计算得到基于CH3和C3H3基添加的由萘(C10H8)到菲(C14H10)详细PAHs生长路径的热力学参数,进一步计算以Arrhenius形式表达的反应速率常数,并对不同生长路径进行了比较.结果表明:环境中自由基参与的脱氢反应比直接脱氢反应更加容易进行,分子结构对脱氢反应、C3H3和CH3加成反应均有较大影响,反应位点处于甲基或亚甲基上的加成反应是无势垒的高放热反应,所有路径的限速步骤均为氢原子转移反应,路径a为反应最优路径.

Study on Growth-Pathway from Naphthalene to Phenanthrene in Soot Nucleation Process

The formation of polycyclic aromatic hydrocarbons(PAHs)in high-temperature environments is an ongoing area of research due to the mismatch between the experimental and simulated concentration profiles of PAHs in flames.In this paper,thermodynamic parameters of PAH growth pathways from naphthalene(C10H8)to phenanthrene(C14H10)via CH3 and C3H3 additions were obtained through quantitative calculations by using M06-2X with 6-311++G(d,p)basis set.In addition,the reaction rate constants of elementary reactions in the modified Arrhenius equation form were calculated,and different growth paths were compared.Results show that H-abstraction reactions via free radical occur more easily than direct hydrogen bonds break.The molecular structures of PAHs have great influences on H-abstraction reactions,as well as C3H3 and CH3 addition reactions.The addition reaction on a methyl or methylene group is highly exothermic without energy barriers.The limiting steps of all the reaction pathways are hydrogen transfer reactions,and the a-path is the optimal path relatively.