ReaxFF molecular dynamics study on pyrolysis of bicyclic compounds for aviation fuel

• Determination of temperature-dependent decomposition mechanisms for novel polycyclic alkanes. • We identify and investigate two major reaction classes- the central bond breaking and ring opening responsible for the initial pyrolysis. • Key atomistic insights on the high-temperature chemistry of these polycyclic alkanes. In this paper, we investigate the initial fuel pyrolysis of four bicyclic compounds, which are potential alternative jet fuels, using ReaxFF force field based molecular dynamics (MD) simulations. These fuels can be separated into two categories, (a) cyclic alkanes attached through a 4-membered ring and (b) cyclic alkanes attached through a single C–C bond. We use a systematic procedure to investigate the reaction chemistry of all these fuel molecules. Global Arrhenius parameters, such as activation energies and pre-exponential factors, are calculated and used to analyze the overall decomposition kinetics of the fuels. The bicyclic fuels have a faster or comparable decomposition rate compared to some existing jet-fuels, such as JP-10. These fuels decompose through two main reaction classes. One pathway is the cleavage of the central bond leading to the formation of two cyclic radicals or species. Second class of reactions involves ring opening leading to the formation of small alkene molecules. The importance of these reactions in fuel decomposition process is found to be highly temperature dependent. This work demonstrates that ReaxFF can be used to investigate pyrolysis and combustion chemistry of existing or future fuels and to potentially contribute to the development of their chemical kinetic models without any a priori input and chemical intuition.