Identification of the hydroperoxide formed by isomerization reactions during the oxidation of n-heptane in a reactor and CFR engine

Sahetchian, Krikor; Rigny, R.; Circan, S.

doi:10.1016/0010-2180(91)90153-3

Cited by 42 publications

(28 citation statements)

References 9 publications

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“…Studies on the stabilized cool flame of n-heptane showed that the maximum concentration of RO 2 radicals [2] and of organic peroxides [3,4] occur before the cool flame, which is in agreement with the maximum concentration of peroxides observed before autoignition of n-pentane, n-heptane, and n-octane in a motored CFR engine [5,6]. Recent works with motored engines [5][6][7][8] showed that ketohydroperoxides play a key role in the ignition process of fuel/air mixtures since the decomposition of these species gives two radicals. Computer modeling studies performed with reduced chemical mechanisms [7,[9][10][11] enabled a fairly good reproduction of the experimental results.…”

Section: Introductionsupporting

confidence: 71%

“…The first investigations on the role of hydroperoxides, in the 1930s, gave evidence of their existence and showed how their formation could be explained [1]. Studies on the stabilized cool flame of n-heptane showed that the maximum concentration of RO 2 radicals [2] and of organic peroxides [3,4] occur before the cool flame, which is in agreement with the maximum concentration of peroxides observed before autoignition of n-pentane, n-heptane, and n-octane in a motored CFR engine [5,6]. Recent works with motored engines [5][6][7][8] showed that ketohydroperoxides play a key role in the ignition process of fuel/air mixtures since the decomposition of these species gives two radicals.…”

Section: Introductionmentioning

confidence: 57%

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Isomeric hexyl‐ketohydroperoxides formed by reactions of hexoxy and hexylperoxy radicals in oxygen

Jorand

Heiss

Perrin

et al. 2003

Int J of Chemical Kinetics

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Isomerization reactions of peroxy radicals during oxidation of long-chain hydrocarbons yield hydroperoxides, and therefore play an important role in combustion and atmospheric chemistry, because of their action as branching agents in these chain reaction processes. Different formation mechanisms and structures are involved. Three isomeric hexyl-ketohydroperoxides are formed via isomerization reactions in oxygen of either hexoxy RO or hexylperoxy RO 2 radicals. In the temperature range 373-473 K, 2-hexoxy (C 6 H 13 O) radical in O 2 /N 2 mixtures gives 2-hexanone-5-hydroperoxide via two consecutive isomerizations. The second one is a H transfer from a HC(OH) group occurring via a seven-membered ring intermediate:Its rate constant has been determined at 453 and 483 K, and the general expression can be written as k = (1.8 ± 1) × 10 10 × exp[−(14300 ± 700)/RT] s −1 (E a in cal mol −1 ) Hexylperoxy C 6 H 13 O 2 radical, present in n-hexane oxidation by oxygen/nitrogen mixtures in the temperature range 543-573 K, gives 2-hexanone-4-hydroperoxide, 3-hexanone-5-hydroperoxide, and 2-hexanone-5-hydroperoxide. The first two are formed through an

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Section: Introductionsupporting

confidence: 71%

Section: Introductionmentioning

confidence: 57%

Isomeric hexyl‐ketohydroperoxides formed by reactions of hexoxy and hexylperoxy radicals in oxygen

Jorand

Heiss

Perrin

et al. 2003

Int J of Chemical Kinetics

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“…The classical low-temperature auto-oxidation reaction scheme presented in Scheme 1 has been confirmed via gas-phase measurements of the key intermediates such as hydroperoxyalkyl radicals [30], alkylhydroperoxides [31,32], large alkenes [32][33][34][35], cyclic ethers [31,34,36,37], and keto-hydroperoxides [33,35,[38][39][40][41][42]. Experiments on liquid-phase auto-oxidation by Korcek and coworkers [43][44][45][46] identified the presence of monohydroperoxides, dihydroperoxides, and keto-hydroperoxides, while recent computational studies [47,48] have shown that subsequent decomposition pathways of keto-hydroperoxides to acids are favorable.…”

Section: Introductionmentioning

confidence: 93%

Additional chain-branching pathways in the low-temperature oxidation of branched alkanes

Wang

Zhang

Moshammer

et al. 2016

Combustion and Flame

100

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a b s t r a c tChain-branching reactions represent a general motif in chemistry, encountered in atmospheric chemistry, combustion, polymerization, and photochemistry; the nature and amount of radicals generated by chainbranching are decisive for the reaction progress, its energy signature, and the time towards its completion. In this study, experimental evidence for two new types of chain-branching reactions is presented, based upon detection of highly oxidized multifunctional molecules (HOM) formed during the gas-phase low-temperature oxidation of a branched alkane under conditions relevant to combustion. The oxidation of 2,5-dimethylhexane (DMH) in a jet-stirred reactor (JSR) was studied using synchrotron vacuum ultraviolet photoionization molecular beam mass spectrometry (SVUV-PI-MBMS). Specifically, species with four and five oxygen atoms were probed, having molecular formulas of C 8 H 14 O 4 (e.g., diketo-hydroperoxide/ketohydroperoxy cyclic ether) and C 8 H 16 O 5 (e.g., keto-dihydroperoxide/dihydroperoxy cyclic ether), respectively. The formation of C 8 H 16 O 5 species involves alternative isomerization of OOQOOH radicals via intramolecular H-atom migration, followed by third O 2 addition, intramolecular isomerization, and OH release; C 8 H 14 O 4 species are proposed to result from subsequent reactions of C 8 H 16 O 5 species. The mechanistic pathways involving these species are related to those proposed as a source of low-volatility highly oxygenated species in Earth's troposphere. At the higher temperatures relevant to auto-ignition, they can result in a net increase of hydroxyl radical production, so these are additional radical chain-branching pathways for ignition. The results presented herein extend the conceptual basis of reaction mechanisms used to predict the reaction behavior of ignition, and have implications on atmospheric gas-phase chemistry and the oxidative stability of organic substances.

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“…A substantial body of literature exists that describes the details of the auto-ignition of the most common transportation fuel surrogate (i.e., n-heptane) under conditions relevant to modern and future engine concepts. These studies report fuel conversion, stable products, and a number of intermediates under various conditions in jet-stirred reactors (JSRs) [6][7][8][9][10][11], flow reactors [12][13][14], flames [15][16][17][18][19][20][21][22][23], and motored engines [24,25]. Reviewing this existing n-heptane oxidation data reveals that a comprehensive analysis of the pool of reactive intermediates is still scarce, especially under lowtemperature and high-pressure conditions; preventing an in-depth understanding of relevant mechanistic pathways and key rate coefficients for reactions controlling ignition and pollutant formation [26].…”

Section: Introductionmentioning

confidence: 99%

n-Heptane cool flame chemistry: Unraveling intermediate species measured in a stirred reactor and motored engine

Wang

Chen

Moshammer

et al. 2018

Combustion and Flame

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Identification of the hydroperoxide formed by isomerization reactions during the oxidation of n-heptane in a reactor and CFR engine

Cited by 42 publications

References 9 publications

Isomeric hexyl‐ketohydroperoxides formed by reactions of hexoxy and hexylperoxy radicals in oxygen

Isomeric hexyl‐ketohydroperoxides formed by reactions of hexoxy and hexylperoxy radicals in oxygen

Additional chain-branching pathways in the low-temperature oxidation of branched alkanes

n-Heptane cool flame chemistry: Unraveling intermediate species measured in a stirred reactor and motored engine

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