Inhibition mechanism of electric field on polycyclic aromatic hydrocarbon formation during n-decane pyrolysis: A ReaxFF MD and DFT study

Abstract

Polycyclic aromatic hydrocarbon (PAH) is the soot precursor in hydrocarbon fuel pyrolysis process, which results in serious combustion and environmental issues. This work investigated the process of n-decane pyrolysis and PAHs formation under electric field using ReaxFF molecular dynamics and density functional theory (DFT) method. The results demonstrated that the electric field increased the decomposition reaction rate constant (k) from 5.15 × 109 s−1 to 9.01 × 109 s−1 and decreased the reaction activation energy (Ea) from 59.47 to 54.79 kcal/mol of n-decane pyrolysis at 0.20 V/Å. DFT calculation validated that the enthalpy change (ΔH) of bonds cracking was decreased and the polarization of n-decane was enhanced by electric field. A priority selective effect was performed on the initial cracking path and validated by the potential energy surfaces (PES). With products distribution statistics, C2 precursors of ring formation were decreased by the field, resulting in the inhibition of largest molecular size growth. The development of the largest molecule structure revealed clearly that the 5-member ring was unstable and the growth of 6-member ring was inhibited under electric field. This work supplies the n-decane pyrolysis and PAH formation mechanism modified by electric field, which provides a wide application in fuel clean combustion and environmental pollution researches.