超临界水氛围下萘开环机理  

Naphthalene rings cleavage mechanism in supercritical water

作　　者：赵浩 张英佳[1] 黄佐华[1] ZHAO Hao;ZHANG Yingjia;HUANG Zuohua(State Key Laboratory of Multiphase Flow in Power Engineering,Xi′an Jiaotong University,Xi′an710049,China)

机构地区：[1]西安交通大学动力工程多相流国家重点实验室,陕西西安710049

出　　处：《洁净煤技术》2023年第10期91-97,共7页Clean Coal Technology

基　　金：国家自然科学基金资助项目(51888103)。

摘　　要：超临界水气化技术是一种煤炭高效清洁低碳利用的新型技术,可以将煤直接转化为氢气、二氧化碳等产物,并将煤中的氮、硫、重金属等污染物以固体无机盐的形式沉淀。芳香烃开环反应是超临界水煤炭气化过程的关键速控步之一,运用分子动力学模拟软件LAMMPS对最简单的多环芳香烃萘,在超临界水氛围、不同温度和当量比下对开环反应过程进行模拟,结合自编程分析了原子键级变化并提取了基元反应,实现了定量化的反应动力学分析。模拟结果表明,萘分子数在高温下呈指数下降,反应速率与当量比呈弱相关。反应路径分析显示,萘的开环路径主要包括热解反应、脱氢反应和OH自由基加成反应,脱氢反应和OH自由基加成反应的通道分支比随着温度降低线性增加。物种通量分析结果表明,氢原子和水分子生成OH自由基和氢气分子反应是OH自由基的主要生成通道,萘分子的热解是氢原子生成的主要通道;水分子热解生成氢原子和OH自由基反应接近平衡,对OH自由基贡献有限。开环反应的定量分析结果可以在超临界水氛围芳香烃详细反应动力学机理上提供参考。Supercritical water gasification technology is a new type of technology for efficient,clean,and low-carbon utilization of coal,which can directly convert coal into products such as hydrogen and carbon dioxide,and precipitate pollutants such as nitrogen,sulfur,and heavy metals in coal in the form of solid inorganic salts.The ring opening reaction of polycyclic aromatic hydrocarbons is one of the rate-determining steps in the supercritical water coal gasification process.The molecular dynamics simulation software(LAMMPS) were performed to study the ring opening reaction process of the simplest PAH naphthalene under supercritical water atmosphere,the different temperatures and equivalence ratios.Combined with self programming analysis of atomic bond level changes and extraction of elementary reactions,the quantitative reaction kinetics analysis was achieved.The simulation results indicate that the number of naphthalene molecules decreases exponentially at high temperatures,and the reaction rate is weakly correlated with the equivalence ratio.The reaction path analysis shows that the ring opening path of naphthalene mainly includes pyrolysis,H atom abstraction,and OH radical addition reactions.The channel branching ratio of dehydrogenation reaction and OH radical addition reaction increases linearly with the decrease in temperature.The species flux analysis indicates that OH radical is mainly from the reaction of ■,while the pyrolysis of naphthalene molecules is the main pathway for hydrogen atom generation.The reaction between hydrogen atoms generated by water molecule pyrolysis and OH radicals is close to equilibrium,rarely contributing to the source of OH radical.The quantitative analysis results of ring opening reactions can provide reference for the detailed reaction kinetics mechanism of aromatic hydrocarbons in supercritical water atmosphere.

关 键 词：分子动力学 多环芳烃 超临界水 反应动力学 反应力场 

分 类 号：TQ53[化学工程—煤化学工程] TK16[动力工程及工程热物理—热能工程]