Formation of polycyclic aromatic hydrocarbons in an atmospheric pressure ethylene diffusion flame

The microstructure of an atmospheric pressure, counterflow, sooting, flat, laminar ethylene diffusion flame has been studied experimentally by withdrawing samples from within the flame using a heated quartz microprobe coupled to an online gas chromatograph/mass spectrometer (GC/MS). The identities and absolute concentrations of about 60 major, minor, and trace species, including aromatics, substituted aromatics, and polycyclic aromatic hydrocarbons (PAH) have been determined. Mole fractions of species quantified were in the range of 0.20 to 10(-7). Benzene was the most abundant aromatic species with the peak level of 450 ppm, whereas naphthalene (90 ppm), phenanthrene (10 ppm), pyrene (35 ppm), and cyclopenta(cd)pyrene (23 ppm) were the most abundant PAHs formed in the flame. The largest PAH detected under the experimental conditions were C18H10 (molecular weight of 226) which include benzo(ghi)fluoranthene and cyclopenta(cd)pyrene. Information provided should be of considerable utility for the development and validation of chemical kinetic mechanisms describing diffusion flames. (C) 1999 by The Combustion Institute.