超临界水氛围下萘开环机理

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 H + H₂O =OH + H₂,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.