Reactive molecular dynamics of pyrolysis and combustion of alternative jet fuels: A ReaxFF study

The current work presents the simulation of the pyrolysis and combustion of alternative jet fuels by reactive force field molecular dynamics methods. A comparison has been done between saturated hydrocarbon farnesane and two unsaturated compounds, alpha-farnesene and beta-farnesene, all of them obtained by the fermentation of sugars present in sugarcane juice. The pyrolysis and combustion mechanisms were elucidated for all the three species at a specified temperature. Significant differences have been observed among the compound reactions during the decompositions. Using a first-order approach, the Arrhenius parameters of the global process were obtained with three different temperatures, held constant over time. For the pyrolysis, the obtained activation energies for farnesane, alpha-farnesene, and beta-farnesene were 132.55, 117.28, and 112.88 kJ mol-1, respectively, and for the combustion, the obtained activation energies were 71.63, 37.99, and 37.98 kJ mol-1, respectively. These data are compatible with the results found in the literature for hydrocarbon fuels. A detailed computational study of all three compounds was performed using the B3LYP/6-311 + G(d,p) approach in the gas phase. Analysis of structures, NBO charges, FMOs, MEP plots, and global reactivity parameters unequivocally supports the simulation results obtained using the ReaxFF code, proving noticeably higher potential reactivity of alpha- and beta-farnesenes compared to farnesane, and furthermore higher reactivity of beta-farnesene compared to alpha-farnesene.