Thermal Hydrogenation and Degradation of Quinoline from Reactive Force Field Simulations

Abstract

AbstractCatalytic hydrogenation is a convenient approach for converting Poly Aromatic Hydrocarbons (PAH) to several small fragments or useful chemicals. In the current study, quinoline is taken as model PAH compound where reactive force field (ReaxFF) simulation is adopted to study its degradation and pyrolytic behavior. To confirm the intermediate and final products, ReaxFF molecular dynamics (MD) simulations at five different temperatures ranging from 2500–4500 K for a total duration of 700 ps were implemented which allows the chemical reactions to be observed at a computationally affordable time scale. Other than 2500 K, all the temperatures provided a pyrolysis scan on the entire quinolone molecule. We have found a qualitative agreement between the previously reported experimental results and our simulation results concerning initiation step of the quinoline hydrogenation along with the formation of major intermediate products such as tetrahydroquinoline (THQ), propylaniline (PA) and decahydroquinoline (DHQ). Further degradation of quinoline with time gives smaller stable products, which include ammonia, ethylene, methane, ethane and acetylene with many intermediates. Most of the intermediate reactions are found to be intramolecular while intermolecular reactions dominate at higher temperatures. Finally, a kinetic analysis was made to obtain the rate constants and activation energies for quinoline hydrogenation.