Laboratory and Theoretical Study of the Oxy Radicals in the OH- and Cl-Initiated Oxidation of Ethene

Orlando, John J.; Tyndall, Geoffrey S.; Bilde, Merete; Ferronato, Corinne; Wallington, Timothy J.; Vereecken, Luc; Peeters, Jozef

doi:10.1021/jp981937d

Cited by 150 publications

(240 citation statements)

References 46 publications

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“…In the troposphere, these two reactions compete [56,[60][61][62]], but at the higher pressures and temperatures of the present study, thermal dissociation dominates, and we assume it to occur instantaneously in the mechanism.…”

Section: Detailed Kinetic Modelmentioning

confidence: 84%

Experimental and kinetic modeling study of C2H4 oxidation at high pressure

López

Rasmussen

Alzueta

et al. 2009

Proceedings of the Combustion Institute

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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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Section: Detailed Kinetic Modelmentioning

confidence: 84%

Experimental and kinetic modeling study of C2H4 oxidation at high pressure

López

Rasmussen

Alzueta

et al. 2009

Proceedings of the Combustion Institute

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“…1,6,24 In contrast, as we discuss below, the 1,4-hydrogen shift in III (Reaction 2) has a barrier of ∼20 kcal/mol. Reaction 2 would therefore appear to be completely negligible under atmospheric conditions.…”

Section: Introductionmentioning

confidence: 93%

Computational Studies of Intramolecular Hydrogen Atom Transfers in the β-Hydroxyethylperoxy and β-Hydroxyethoxy Radicals

et al. 2007

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The -hydroxyethylperoxy (I) and -hydroxyethoxy (III) radicals are prototypes of species that can undergo hydrogen atom transfer across their intramolecular hydrogen bonds. These reactions may play an important role in both the atmosphere and in combustion systems. We have used density functional theory and composite electronic structure methods to predict the energetics of these reactions, RRKM/master equation simulations to model the kinetics of chemically activated I, and variational transition state theory (TST) to predict thermal rate constants for the 1,5-hydrogen shift in I (Reaction 1) and the 1,4-hydrogen shift in III (Reaction 2). Our multi-coefficient Gaussian-3 calculations predict that Reaction 1 has a barrier of 23.59 kcal/mol, and that Reaction 2 has a barrier of 22.71 kcal/mol. These predictions agree rather well with the MPW1K and BB1K density functional theory predictions but disagree with predictions based on B3LYP energies or geometries. Our RRKM/master equation simulations suggest that almost 50% of I undergoes a prompt hydrogen shift reaction at pressures up to 10 Torr, but the extent to which I is chemically activated is uncertain. For Reaction 1 at 298 K, the variational TST rate constant is ∼30% lower than the conventional TST result, and the microcanonical optimized multidimensional tunneling (µOMT) method predicts that tunneling accelerates the reaction by a factor of 3. TST calculations on Reaction 2 reveal no variational effect and a 298 K µOMT transmission coefficient of 10 5 . The Eckart method overestimates transmission coefficients for both reactions.

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“…The remaining 10% is removed by O 3 . The oxidation of C 2 H 4 in the termolecular reaction with OH is very complex (Niki et al, 1981;Barnes et al, 1993;Orlando et al, 1998). In the first step of this reaction sequence, the hydroxyl radical adds to the double bond followed by O 2 addition to the other end to form a peroxy radical, HOCH 2 CH 2 O 2 .…”

Section: Chemical Reaction Pathwaymentioning

confidence: 99%

A consistent molecular hydrogen isotope chemistry scheme based on an independent bond approximation

2009

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Abstract. The isotopic composition of molecular hydrogen (H 2 ) produced by photochemical oxidation of methane (CH 4 ) and Volatile Organic Compounds (VOCs) is a key quantity in the global isotope budget of (H 2 ). The many individual reaction steps involved complicate its investigation. Here we present a simplified structure-activity approach to assign isotope effects to the individual elementary reaction steps in the oxidation sequence of CH 4 and some other VOCs. The approach builds on and extends the work by Gerst and Quay (2001) and Feilberg et al. (2007b). The description is generalized and allows the application, in principle, also to other compounds. The idea is that the C-H and C-D bonds -seen as reactive sites -have similar relative reaction probabilities in isotopically substituted, but otherwise identical molecules. The limitations of this approach are discussed for the reaction CH 4 +Cl. The same approach is applied to VOCs, which are important precursors of H 2 that need to be included into models. Unfortunately, quantitative information on VOC isotope effects and source isotope signatures is very limited and the isotope scheme at this time is limited to a strongly parameterized statistical approach, which neglects kinetic isotope effects. Using these concepts we implement a full hydrogen isotope scheme in a chemical box model and carry out a sensitivity study to identify those reaction steps and conditions that are most critical for the isotope composition of the final H 2 product. The reaction scheme is directly applicable in global chemistry models, which can thus include the isotope pathway of H 2 produced from CH 4 and VOCs in a consistent way.

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Laboratory and Theoretical Study of the Oxy Radicals in the OH- and Cl-Initiated Oxidation of Ethene

Cited by 150 publications

References 46 publications

Experimental and kinetic modeling study of C2H4 oxidation at high pressure

Experimental and kinetic modeling study of C2H4 oxidation at high pressure

Computational Studies of Intramolecular Hydrogen Atom Transfers in the β-Hydroxyethylperoxy and β-Hydroxyethoxy Radicals

A consistent molecular hydrogen isotope chemistry scheme based on an independent bond approximation

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