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Toward the Oxidation of the Phenyl Radical and Prevention of PAH Formation in Combustion Systems

Journal Article · · Journal of Physical Chemistry. A, Molecules, Spectroscopy, Kinetics, Environment, and General Theory
DOI:https://doi.org/10.1021/jp509170x· OSTI ID:1602912
 [1];  [2];  [3];  [3];  [3];  [4]
  1. Univ. of Hawaii at Manoa, Honolulu, HI (United States); University of Hawaii at Manoa
  2. Univ. of Hawaii at Manoa, Honolulu, HI (United States)
  3. Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States)
  4. Florida International Univ., Miami, FL (United States)
+ Show Author Affiliations

The reaction of the phenyl radical (C6H5) with molecular oxygen (O2) plays a central role in the degradation of poly- and monocyclic aromatic radicals in combustion systems which would otherwise react with fuel components to form polycyclic aromatic hydrocarbons (PAHs) and eventually soot. Despite intense theoretical and experimental scrutiny over half a century, the overall reaction channels have not all been experimentally identified. Tunable vacuum ultraviolet photoionization in conjunction with a combustion simulating chemical reactor uniquely provides the complete isomer specific product spectrum and branching ratios of this prototype reaction. In the reaction of phenyl radicals and molecular oxygen at 873 K and 1003 K, ortho-benzoquinone (o-C6H4O2), the phenoxy radical (C6H5O), and cyclopentadienyl radical (C5H5) were identified as primary products formed through emission of atomic hydrogen, atomic oxygen and carbon dioxide. Furan (C4H4O), acrolein (C3H4O), and ketene (C2H2O) were also identified as primary products formed through ring opening and fragmentation of the 7-membered ring 2-oxepinoxy radical. Secondary reaction products para-benzoquinone (p-C6H4O2), phenol (C6H5OH), cyclopentadiene (C5H6), 2,4-cyclopentadienone (C5H4O), vinylacetylene (C4H4), and acetylene (C2H2) were also identified. The pyranyl radical (C5H5O) was not detected; however, electronic structure calculations show that it is formed and isomerizes to 2,4-cyclopentadienone through atomic hydrogen emission. In combustion systems, barrierless phenyl-type radical oxidation reactions could even degrade more complex aromatic radicals. Lastly, an understanding of these elementary processes is expected to lead to a better understanding toward the elimination of carcinogenic, mutagenic, and environmentally hazardous byproducts of combustion systems such as PAHs.

Research Organization:
Univ. of Hawaii at Manoa, Honolulu, HI (United States)
Sponsoring Organization:
USDOE Office of Science (SC), Basic Energy Sciences (BES) (SC-22)
Grant/Contract Number:
FG02-03ER15411; FG02-04ER15570; AC02-05CH11231
OSTI ID:
1602912
Journal Information:
Journal of Physical Chemistry. A, Molecules, Spectroscopy, Kinetics, Environment, and General Theory, Journal Name: Journal of Physical Chemistry. A, Molecules, Spectroscopy, Kinetics, Environment, and General Theory Journal Issue: 28 Vol. 119; ISSN 1089-5639
Publisher:
American Chemical SocietyCopyright Statement
Country of Publication:
United States
Language:
English

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Cited By (5)

Dehydro-oxazole, thiazole and imidazole radicals: insights into the electronic structure, stability and reactivity aspects journal January 2017
A combined crossed molecular beams and computational study on the formation of distinct resonantly stabilized C 5 H 3 radicals via chemically activated C 5 H 4 and C 6 H 6 intermediates journal January 2018
Product detection study of the gas-phase oxidation of methylphenyl radicals using synchrotron photoionisation mass spectrometry journal January 2019
How to add a five-membered ring to polycyclic aromatic hydrocarbons (PAHs) – molecular mass growth of the 2-naphthyl radical (C 10 H 7 ) to benzindenes (C 13 H 10 ) as a case study journal January 2019
Enabling liquid vapor analysis using synchrotron VUV single photon ionization mass spectrometry with a microfluidic interface journal November 2018

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Related Subjects

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY
Carbon
Chemical reactions
Inorganic carbon compounds
Oxides
Oxygen