Unimolecular Reactions of Peroxy Radicals in Atmospheric Chemistry and Combustion

Glowacki, David R.; Pilling, Michael J.

doi:10.1002/cphc.201000469

Cited by 79 publications

(94 citation statements)

References 39 publications

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“…However, the fast reaction with O 2 is the major consumption step, even at higher temperatures. Alzueta et al identified the chain‐propagating sequence

\begin{matrix} true \\ right C_{2} H_{2} \overset{+ OH}{⟶} C_{2} H_{2} OH \overset{+ O_{2}}{⟶} OCHCHO + OH \end{matrix}

as important for the onset of reaction for C 2 H 2 at atmospheric pressure and temperatures above 700 K. Interest in this oxidation pathway for atmospheric chemistry has spawned a range of experimental and theoretical studies on the C 2 H 2 + OH + O 2 reaction at low temperature . Hatakeyama et al showed in smoke‐chamber experiments that the reaction generates glyoxal and formic acid,

\begin{matrix} true \\ right CHCHOH + O_{2} ⇄ OCHCHO + OH \end{matrix}

\begin{matrix} true \\ right CHCHOH + O_{2} ⇄ HOCHO + HCO \end{matrix}

…”

Section: Detailed Kinetic Modelmentioning

confidence: 99%

Experimental and Kinetic Modeling Study of C₂H₂ Oxidation at High Pressure

Giménez-López

Rasmussen

Hashemi

et al. 2016

Int J of Chemical Kinetics

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A detailed chemical kinetic model for oxidation of C 2 H 4 in the intermediate temperature range and high pressure has been developed and validated experimentally. New ab initio calculations and RRKM analysis of the important C 2 H 3 + O 2 reaction was was used to obtain rate coefficients over a wide range of conditions (0.003-100 bar, 200-3000 K). The results indicate that at 60 bar vinyl peroxide, rather than CH 2 O and HCO, is the dominant product.The experiments, involving C 2 H 4 /O 2 mixtures diluted in N 2 , were carried out in a high pressure flow reactor at 600-900 K and 60 bar, varying the reaction stoichiometry from very lean to fuel-rich conditions. Model predictions are generally satisfactory. The governing reaction mechanisms are outlined based on calculations with the kinetic model. Under the investigated conditions the oxidation pathways for C 2 H 4 are more complex than those prevailing at higher temperatures and lower pressures. The major differences are the importance of the hydroxyethyl (CH 2 CH 2 OH) and 2-hydroperoxyethyl 1 (CH 2 CH 2 OOH) radicals, formed from addition of OH and HO 2 to C 2 H 4 , and vinyl peroxide, formed from C 2 H 3 + O 2 . Hydroxyethyl is oxidized through the peroxide HOCH 2 CH 2 OO (lean conditions) or through ethenol (low O 2 concentration), while 2-hydroperoxyethyl is converted through oxirane. [2][3][4][5][6][7], shock tubes [8][9][10][11][12] and premixed laminar flames [13][14][15][16][17], covering a wide range of stoichiometries and temperatures. Most of the reported work, however, have been carried out at near atmospheric pressure. A few results are available from flow reactor studies at 5-10 bar [6], but despite their relevance for the chemistry in engines, gas turbines, and gas-to-liquid processes, data at high pressures are limited.The objective of the present study is to obtain experimental results for the oxidation of C 2 H 4 at high pressure (60 bar) as functions of temperature (600-900 K) and stoichiometry (lean to fuel-rich) and analyze them in terms of a detailed chemical kinetic model. The oxidation pathways for C 2 H 4 under these conditions are different from those prevailing at higher temperatures and lower pressures and the results of the current work help to extend the validation range for chemical kinetic modeling of C 2 H 4 oxidation. This paper is part of a series investigating the high-pressure, medium temperature oxidation of simple fuels: previously work has been reported for CO/H 2 , CH 4 , and CH 4 /C 2 H 6 mixtures [18,19]. The present kinetic model draws on this work, as well as recent results in tropospheric chemistry. Furthermore, the important reaction of C 2 H 3 with O 2 was characterized from ab initio calculations over a wide range of pressure and temperature. 3 ExperimentalThe experimental setup is a laboratory-scale high pressure laminar flow reactor designed to approximate plug-flow. The setup is described in detail elsewhere [18] and only a brief description is provided here. The system enables well-defined investigations of...

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“…However, the fast reaction with O 2 is the major consumption step, even at higher temperatures. Alzueta et al identified the chain‐propagating sequence

\begin{matrix} true \\ right C_{2} H_{2} \overset{+ OH}{⟶} C_{2} H_{2} OH \overset{+ O_{2}}{⟶} OCHCHO + OH \end{matrix}

\begin{matrix} true \\ right CHCHOH + O_{2} ⇄ OCHCHO + OH \end{matrix}

\begin{matrix} true \\ right CHCHOH + O_{2} ⇄ HOCHO + HCO \end{matrix}

…”

Section: Detailed Kinetic Modelmentioning

confidence: 99%

Experimental and Kinetic Modeling Study of C₂H₂ Oxidation at High Pressure

Giménez-López

Rasmussen

Hashemi

et al. 2016

Int J of Chemical Kinetics

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“…By comparison, the canopy-averaged total OH production rate in the base scenario is 3.8 pptv s −1 . It is possible that our simple mechanism has neglected additional sinks of VRO 2 radicals, such as unimolecular isomerization/decomposition (Glowacki and Pilling, 2010) or surface deposition, which would reduce the buildup of VRO 2 in the canopy. For example, VRO 2 concentrations decrease by 20 % when we force VRO 2 to deposit at the aerodynamic limit, though even this loss would be insufficient to bring the modeled NO/NO 2 ratio for the y = 0.75 case into the range expected for this forest.…”

Section: Ro X Chemistrymentioning

confidence: 99%

Forest-atmosphere exchange of ozone: sensitivity to very reactive biogenic VOC emissions and implications for in-canopy photochemistry

et al. 2011

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Abstract. Understanding the fate of ozone within and above forested environments is vital to assessing the anthropogenic impact on ecosystems and air quality at the urbanrural interface. Observed forest-atmosphere exchange of ozone is often much faster than explicable by stomatal uptake alone, suggesting the presence of additional ozone sinks within the canopy. Using the Chemistry of AtmosphereForest Exchange (CAFE) model in conjunction with summer noontime observations from the 2007 Biosphere Effects on Aerosols and Photochemistry Experiment (BEARPEX-2007), we explore the viability and implications of the hypothesis that ozonolysis of very reactive but yet unidentified biogenic volatile organic compounds (BVOC) can influence the forest-atmosphere exchange of ozone. Nonstomatal processes typically generate 67 % of the observed ozone flux, but reactions of ozone with measured BVOC, including monoterpenes and sesquiterpenes, can account for only 2 % of this flux during the selected timeframe. By incorporating additional emissions and chemistry of a proxy for very reactive VOC (VRVOC) that undergo rapid ozonolysis, we demonstrate that an in-canopy chemical ozone sink of ∼2 × 10 8 molec cm −3 s −1 can close the ozone flux budget. Even in such a case, the 65 min chemical lifetime of ozone is much longer than the canopy residence time of ∼2 min, highlighting that chemistry can influence reactive trace gas exchange even when it is "slow" relative to vertical mixing. This level of VRVOC ozonolysis could enhance OH and RO 2 production by as much as 1 pptv s −1 and substantially alter their respective vertical profiles depending on the acCorrespondence to: J. A. Thornton (thornton@atmos.washington.edu) tual product yields. Reaction products would also contribute significantly to the oxidized VOC budget and, by extension, secondary organic aerosol mass. Given the potentially significant ramifications of a chemical ozone flux for both incanopy chemistry and estimates of ozone deposition, future efforts should focus on quantifying both ozone reactivity and non-stomatal (e.g. cuticular) deposition within the forest.

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“…The addition of the OH radical to the aromatic ring results in the formation of a hydroxycyclohexadienyl-type radical (Bohn, 2001;Molina et al, 1999). Under atmospheric conditions this reacts with O 2 to yield peroxy radicals or phenolic compounds (Calvert et al, 2002;Glowacki and Pilling, 2010;Suh et al, 2003). When aromaticity is lost by OH addition, nonaromatic double bonds are formed representing highly reactive products to more oxidants, which is a peculiar behavior not observed in other classes of VOCs (Calvert et al, 2002), This behavior makes the investigation of ArHC oxidation more complex.…”

Section: Introductionmentioning

confidence: 99%

Formation of highly oxygenated organic molecules from aromatic compounds

et al. 2018

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Abstract. Anthropogenic volatile organic compounds (AVOCs) often dominate the urban atmosphere and consist to a large degree of aromatic hydrocarbons (ArHCs), such as benzene, toluene, xylenes, and trimethylbenzenes, e.g., from the handling and combustion of fuels. These compounds are important precursors for the formation of secondary organic aerosol. Here we show that the oxidation of aromatics with OH leads to a subsequent autoxidation chain reaction forming highly oxygenated molecules (HOMs) with an O : C ratio of up to 1.09. This is exemplified for five single-ring ArHCs (benzene, toluene, o-/m-/p-xylene, mesitylene (1,3,5-trimethylbenzene) and ethylbenzene), as well as two conjugated polycyclic ArHCs (naphthalene and biphenyl). We report the elemental composition of the HOMs and show the differences in the oxidation patterns of these ArHCs. A potential pathway for the formation of these HOMs from aromatics is presented and discussed. We hypothesize that AVOCs may contribute substantially to new particle formation events that have been detected in urban areas.

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Unimolecular Reactions of Peroxy Radicals in Atmospheric Chemistry and Combustion

Cited by 79 publications

References 39 publications

Experimental and Kinetic Modeling Study of C₂H₂ Oxidation at High Pressure

Experimental and Kinetic Modeling Study of C₂H₂ Oxidation at High Pressure

Forest-atmosphere exchange of ozone: sensitivity to very reactive biogenic VOC emissions and implications for in-canopy photochemistry

Formation of highly oxygenated organic molecules from aromatic compounds

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Unimolecular Reactions of Peroxy Radicals in Atmospheric Chemistry and Combustion

Cited by 79 publications

References 39 publications

Experimental and Kinetic Modeling Study of C2H2 Oxidation at High Pressure

Experimental and Kinetic Modeling Study of C2H2 Oxidation at High Pressure

Forest-atmosphere exchange of ozone: sensitivity to very reactive biogenic VOC emissions and implications for in-canopy photochemistry

Formation of highly oxygenated organic molecules from aromatic compounds

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Product

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Experimental and Kinetic Modeling Study of C₂H₂ Oxidation at High Pressure

Experimental and Kinetic Modeling Study of C₂H₂ Oxidation at High Pressure