| Polycyclic aromatic hydrocarbons（PAH）are endothermic hydrocarbon fuel coking precursors,which can be produced by the dehydrogenation of cyclic olefins.In this paper,the method of Quantum Chemical calculation and RRKM/master equation is used to analyze the ring formation mechanism between 1,3-butadiene and ethylene,isoprene and ethylene,2-naphthyl and 1,3-butadiene,and dynamics of ring growth for them are simulated.Using M062X/MG3S,B2PLYP/TZVP,B2PLYPD/TZVP and B2PLYPD3/TZVP quantum chemistry calculations to study the cycloaddition reaction of 1,3-butadiene with ethylene,the results show that the synergistic path is a thermodynamically favorable path.The second stable conformation of the butadiene is the twisted conformation,and the energy is 11–13 k J mol-1higher than the trans conformation.The micro-canonical transition state theory shows that the cooperative path is also a dynamic favorable path in the research scope.The results of the RRKM/master equation method show that 1,3-butadiene and ethylene have a strong pressure dependence on temperature and pressure within the temperature range of 800 K–2000 K and the pressure range of 0.01 atm–10 atm.Ethylene and isoprene can generate 1-methyl-1-cyclohexene through a cooperative path and a non-cooperative path.The results of quantitative calculation and RRKM/master equation method indicate that the cooperative path is a kinetic and thermodynamically favorable path.The influence of methyl makes the energy change of isoprene C=C-C=C when the dihedral angle is twisted is higher than that of 1,3-butadiene.As the temperature of the system increases,the pressure to reach the high-pressure limit rate constant also increases.When the system pressure is higher than 1 atm,the reverse reaction rate constant is only temperature dependent in the temperature range of 700 K-1500 K.When the system pressure is higher than 10 atm,the forward and reverse reaction rate constants are independent of pressure.Calculating the potential energy surface of 2-naphthyl and 1,3-butadiene at the level of DLPNO-CCSD（T）/M062X,the entry energy barrier of the path to 1,4-dihydrophenanthrene is the lowest,followed by vinyl naphthalene,naphthalene energy barrier is the highest.The kinetic calculation shows that the intermediates W1 and W2 are the main products at low temperature,and 1,4-dihydrophenanthrene is formed from the intermediate W3 in the late stage of the reaction.The total reaction rate constant is calculated in the range of 0.03 atm-100 atm.The rate constant below 1000 K is related to temperature and pressure.Naphthalene and free radicals are the main products above 1000 K,and the rate constant is only related to temperature.These results indicate that the production and growth of polycyclic aromatic hydrocarbons are heavily dependent on the environment in which the system is located.Quantitative and kinetic simulations can provide theoretical guidance for the actual fuel coking process. |
