Formation mechanism of polycyclic aromatic hydrocarbons and fullerenes in premixed benzene flames
A better understanding of the formation of polycyclic aromatic hydrocarbons (PAH) and fullerenes is of practical interest due to the apparent environmental health effects of many PAH and potential industrial applications of fullerenes. In the present work, a kinetic model describing the growth of PAH up to coronene (C{sub 24}H{sub 12}) and of C{sub 60} and C{sub 70} fullerenes is developed. Comparison of the model predictions with concentration profiles in a nearly sooting low-pressure premixed, laminar, one-dimensional benzene/oxygen/argon flame (equivalence ratio {phi} = 1.8, pressure = 2.67 kPa) measured by Bittner using a molecular beam system coupled to mass spectrometry shows reasonably good predictive capability for stable and radical intermediates and growth species up to C{sub 16}H{sub 10} isomers. Cyclopentadienyl is found to be a key species for naphthalene formation. The further growth process is based on H abstraction and acetylene addition but also the contribution of small PAH is considered. Good to fair agreement between model predictions and experimental data for larger PAH including the different C{sub 16}H{sub 10} isomers obtained by gas chromatography coupled to mass spectrometry and high performance liquid chromatography could be achieved for PAH in a sooting low-pressure premixed, laminar, one-dimensional benzene/oxygen/argon flame ({phi} = 2.4, 5.33 kPa). C{sub 60} and C{sub 70} fullerenes are underpredicted, and possible reasons such as uncertainties in rate coefficients or the existence of other formation pathways are discussed. PAH depletion in the burnt gas is not reproduced by the model and is believed to involve supplementary sinks such as reactions involving PAH and growing soot particles.
- Research Organization:
- Massachusetts Inst. of Tech., Cambridge, MA (US)
- Sponsoring Organization:
- USDOE; National Institute of Environmental Health Sciences; National Aeronautics and Space Administration
- DOE Contract Number:
- FG02-84ER13282
- OSTI ID:
- 20000572
- Journal Information:
- Combustion and Flame, Vol. 119, Issue 1-2; Other Information: PBD: Oct 1999; ISSN 0010-2180
- Country of Publication:
- United States
- Language:
- English
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