Formation mechanisms of aromatic compounds in aliphatic flames

Cole, Julia A.; Bittner, J.D.; Longwell, John P.; Howard, Jack B.

doi:10.1016/0010-2180(84)90005-1

Cited by 243 publications

(151 citation statements)

References 30 publications

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“…Evidently, the existence of active surface sites of these grains promotes C 6 H 6 production, thus allowing PAHs to form at lower temperature. Based on the literature on the formation of benzene [3,48,49] and the intermediates observed in our TOF-MS measurements, we speculate that the reaction paths for benzene generation are as shown in schemes 1 and 2 with the recombination of propargyl radicals (C 3 H 3 ) leading to formation of benzene or the phenyl radical and a hydrogen atom, as shown in scheme 2. Owing to the presence of vinyl-acetylene (C 4 H 4 ), two other pathways to benzene closure involving the reaction of 1-buten-3-ynyl (1-C 4 H 3 ) with acetylene and 1,3-butadienyl (1-C 4 H 5 ) with acetylene [49,50] cannot be excluded.…”

Section: (C) Reaction Mechanisms and Pathwaysmentioning

confidence: 54%

Catalytic conversion of acetylene to polycyclic aromatic hydrocarbons over particles of pyroxene and alumina

Tian

Liu

Hammonds

et al. 2013

Phil. Trans. R. Soc. A.

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Polycyclic aromatic hydrocarbons (PAHs) are known to be present in many astrophysical objects and environments, but our understanding of their formation mechanism(s) is far from satisfactory. In this paper, we describe an investigation of the catalytic conversion reaction of acetylene gas to PAHs over pyroxene and alumina. Crystalline silicates such as pyroxenes (with general formula [Mg, Fe]SiO 3 ) and alumina (Al 2 O 3 ) are observed astrophysically through their infrared spectra and are likely to promote grain surface chemical reactions. In the experiments reported here, gas-phase PAHs were produced by the catalytic reaction of acetylene over crystalline silicates and alumina using a pulsed jet expansion technique and the gaseous products detected using time-of-flight mass spectrometry. In a separate experiment, the catalytic formation of PAHs from acetylene was further confirmed with acetylene gas at atmospheric pressure flowing continuously through a fixed-bed reactor. The gas effluent and carbonaceous compounds deposited on the catalysts were dissolved separately in dichloromethane and analysed using gas chromatography–mass spectrometry. Among the samples studied, alumina showed higher activity than the pyroxene-type grains for the acetylene reaction. It is proposed that formation of the PAHs relies on the Mg 2+ ions in the pyroxenes and Al 3+ ions in alumina, where these ions act as Lewis acid sites. X-ray diffraction, Fourier transform infrared and high-resolution transmission electron microscopy techniques were used to characterize the structure and physical properties of the pyroxene and alumina samples.

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Section: (C) Reaction Mechanisms and Pathwaysmentioning

confidence: 54%

Catalytic conversion of acetylene to polycyclic aromatic hydrocarbons over particles of pyroxene and alumina

Tian

Liu

Hammonds

et al. 2013

Phil. Trans. R. Soc. A.

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“…In the literature, the formation of benzene is mostly related to the reactions of C 2 (acetylene), C 3 or C 4 unsaturated species [2][3][4][5][6]. Nevertheless, some papers suggest a link between C 6 and C 5 cyclic species [1,7,8].…”

Section: Introductionmentioning

confidence: 99%

Rich methane premixed laminar flames doped by light unsaturated hydrocarbons

Gueniche

Glaude

Fournet

et al. 2008

Combustion and Flame

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In line with the studies presented in the parts I and II of this paper, the structure of a laminar rich premixed methane flame doped with cyclopentene has been investigated. The gases of this flame contains 15.3% (molar) of methane, 26.7% of oxygen and 2.4% cyclopentene corresponding to an equivalence ratio of 1.79 and a ratio C 5 H 8 / CH 4 of 16 %. The flame has been stabilized on a burner at a pressure of 6.7 kPa using argon as dilutant, with a gas velocity at the burner of 36 cm/s at 333 K. The temperature ranged from 627 K close to the burner up to 2027 K. Quantified species included usual methane C 0 -C 2 combustion products, but also propyne, allene, propene, propane, 1-butene, 1,3-butadiene, 1,2-butadiene, vinylacetylene, diacetylene, cyclopentadiene, 1,3-pentadiene, benzene and toluene. A new mechanism for the oxidation of cyclopentene has been proposed. The main reaction pathways of consumption of cyclopentene and of formation of benzene and toluene have been derived from flow rate analyses.

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Section: Introductionmentioning

confidence: 99%

“…The formation of soot precursors and PAH in combustion involves small unsaturated hydrocarbons, the chemistry of which is still very uncertain. Different reaction pathways have been proposed for the formation and the oxidation of the first aromatic compounds, involving the reactions of C 2 (acetylene), C 3 or C 4 unsaturated species [1][2][3][4][5].As the determinant role of propargyl radicals in forming benzene, the first aromatic ring, is now well accepted, it is important to better understand their reactions. With that purpose, the oxidation of allene (propadiene) and propyne has been already studied in several oxidation conditions: shock tubes [6][7][8], flow reactor [9,10], jet-stirred reactor [7,11] and premixed flames [10,11].…”

mentioning

confidence: 99%

Rich methane premixed laminar flames doped with light unsaturated hydrocarbonsI. Allene and propyne

Gueniche

Glaude

Dayma

et al. 2006

Combustion and Flame

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The structure of three laminar premixed rich flames have been investigated: a pure methane flame and two methane flames doped by allene and propyne, respectively. The gases of the three flames contain 20.9% (molar) of methane and 33.4 % of oxygen corresponding to an equivalent ratio of 1.25 for the pure methane flame. In both doped flames, 2.49 % of C 3 H 4 was added, corresponding to a ratio C 3 H 4 / CH 4 of 12 % and an equivalent ratio of 1.55. The three flames have been stabilized on a burner at a pressure of 6.7 kPa using argon as dilutant, with a gas velocity at the burner of 36 cm/s at 333 K. The concentration profiles of stable species were measured by gas chromatography after sampling with a quartz microprobe. Quantified species included carbon monoxide and dioxide, methane, oxygen, hydrogen, ethane, ethylene, acetylene, propyne, allene, propene, propane, 1,2-butadiene, 1,3-butadiene, 1-butene, iso-butene, 1-butyne, vinylacetylene and benzene. The temperature was measured using a thermocouple in PtRh (6%)-PtRh (30%) settled inside the enclosure and ranged from 700K close to the burner up to 1850K. In order to model these new results, some improvements have been made to a mechanism previously developed in our laboratory for the reactions of C 3 -C 4 unsaturated hydrocarbons. The main reaction pathways of consumption of allene and propyne and of formation of C 6 aromatic species have been derived from flow rate analyses.Keywords : Premixed laminar flame, methane, allene, propyne, modeling. 3 INTRODUCTIONSoots and polyaromatic hydrocarbons (PAH), which are present in the exhaust gas of diesel engine, represent a high part of the urban pollution. Many efforts have then been focused on reducing the emissions of these compounds. The formation of soot precursors and PAH in combustion involves small unsaturated hydrocarbons, the chemistry of which is still very uncertain. Different reaction pathways have been proposed for the formation and the oxidation of the first aromatic compounds, involving the reactions of C 2 (acetylene), C 3 or C 4 unsaturated species [1][2][3][4][5].As the determinant role of propargyl radicals in forming benzene, the first aromatic ring, is now well accepted, it is important to better understand their reactions. With that purpose, the oxidation of allene (propadiene) and propyne has been already studied in several oxidation conditions: shock tubes [6][7][8], flow reactor [9,10], jet-stirred reactor [7,11] and premixed flames [10,11]. Previous works in flames include studies of the influence of the addition of allene on The purpose of the present paper is to experimentally investigate the structures of two premixed laminar methane flames containing propadiene and propyne, respectively, and to compare them with that of a pure methane flame containing the same mole fractions of methane and oxygen. The use of a methane flame will allow us to have a reactive mixture rich in methyl radicals and to be more representative of combustion mixtures containing larger hydrocarbons than hydrogen or ...

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Formation mechanisms of aromatic compounds in aliphatic flames

Cited by 243 publications

References 30 publications

Catalytic conversion of acetylene to polycyclic aromatic hydrocarbons over particles of pyroxene and alumina

Catalytic conversion of acetylene to polycyclic aromatic hydrocarbons over particles of pyroxene and alumina

Rich methane premixed laminar flames doped by light unsaturated hydrocarbons

Rich methane premixed laminar flames doped with light unsaturated hydrocarbonsI. Allene and propyne

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