Probing PAH formation chemical kinetics from benzene and toluene pyrolysis in a single-pulse shock tube

Benzene and toluene were pyrolyzed under highly argon-diluted conditions at a nominal pressure of 20 bar in single-pulse shock tube coupled to gas chromatography/gas chromatography–mass spectrometry (GC/GC–MS) diagnostics. Concentration evolutions polycyclic aromatic hydrocarbon (PAH) intermediates measured temperature range 1100–1800 K by analyzing the post-shock mixtures. Different PAH speciation behaviors, regarding types, concentrations formation windows, observed two reaction systems. A kinetic model was proposed predict interpret measurements. Through combination experimental modeling efforts, patterns from species pools benzene pyrolysis illustrated. In both cases, channels leading PAHs basically originate respective fuel radicals, phenyl benzyl. Due higher thermal stability benzene, production phenyl, thus most species, occur comparison case toluene. pyrolysis, benzyne participates crucial such as naphthalene acenaphthylene. Phenyl self-recombination takes considerable carbon flux into biphenyl, which serves an important intermediate acenaphthylene through hydrogen loss ring closure. The resonantly-stabilized benzyl is abundant its decomposition further produces other radicals fulvenallenyl propargyl. Barrierless addition reactions among these are found be sources PAHs. Fuel-specific pathways have pronounced effects on particularly lower temperatures where depletion not completed within time 4.0 ms. Contributions commonly existing Hydrogen-Abstraction-Carbon-Addition (HACA) routes increase with cases.