Study on PAHs and PM Formed by Benzene Pyrolysis

The main component of PM (particulate matter) formed in the combustion field is soot. Soot is formed by pyrolysis, polymerization and partial oxidation of hydrocarbon fuel. In this experimental research, the effects of temperature and oxygen on PAHs (polycyclic aromatic hydrocarbons) and PM formed from benzene-oxygen mixture were investigated by independent control of temperature (T_f = 1,073 K, 1,173 K, 1,273 K, and 1,338 K) and oxygen concentration (ϕ = ∞, 6.2, and 2.8). In order to investigate the growth processes of PAHs, mass concentrations of naphthalene, biphenyl, phenanthrene, anthracene, and pyrene were measured. As the result, it was found that mass concentration of biphenyl (two-ring PAH, n_C = 12) was higher than naphthalene (two-ring PAH, n_C = 10) under benzene-N₂ mixture condition (without oxygen condition:ϕ = ∞). Mass concentrations of biphenyl and naphthalene were almost same levels under ϕ = 6.2 condition. Furthermore, under ϕ = 2.8 condition, mass concentration of naphthalene was higher than that of biphenyl. Biphenyl and naphthalene concentration change was obvious at 1,250±20 K. Under low temperature condition of 1,190 K, small amount of PM was formed from benzene pyrolysis without oxygen and PM concentration increased with an addition of oxygen. When the temperature increased over 1,310 K, much of PM was formed and it had no difference in with and without oxygen.