Primary Product Distribution from the Reaction of Hydroxyl Radicals with Toluene at ppb NOX Mixing Ratios |
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| Authors: | D F Smith C D McIver T E Kleindienst |
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| Institution: | (1) ManTech Environmental Sciences, PO Box 12313, Research Triangle Park, NC, 27709, U.S.A. |
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| Abstract: | A study has been conducted to examine the OH-initiated degradation products of toluene in the presence of sub part-per-million levels of NOX. The experiments were conducted in a dynamic reactor to minimize the conversion of the aromatic compounds while allowing a sufficient mass of products to be collected for analysis. The major primary products detected in the toluene system (with molar yields) include glyoxal (0.238), methylglyoxal (0.167), o-cresol (0.120), benzaldehyde (0.06), 4-oxo-2-pentenal (0.03), and p-cresol (0.03). Six other reaction products, most being ring cleavage products, were measured at yields below 3%. Corrections for secondary OH reactions with the products were made where necessary. The formation of the cresol isomers was found to be invariant to the NO2 concentrations which indicates that under atmospheric conditions the initial hydroxycyclohexadienyl radical reaction with NO2 is a minor process and that most of the reaction occurs with O2. The product yields found in this study are expected to be representative of those that occur in the urban atmosphere at ambient NO2 concentrations. |
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| Keywords: | toluene photooxidation mechanism aromatic hydrocarbon OH reactions ring-cleavageproducts ring-retaining products |
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