A Quantum Chemistry Study of the Formation of Pah and Soot Precursors Through Butadiene Reactions

Cavallotti, Carlo; Fascella, Simone; Rota, Renato; Carrà, Sergio

doi:10.1080/00102200490428026

Cited by 12 publications

(16 citation statements)

References 14 publications

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“…Thus, at 1 atm, the formation of c-C 5 H 6 + CH 3 is negligible, in contrast to previous predictions by Cavallotti et al 20,21 As noted in previous works and also illustrated in Figure 4, there remains a great deal of disparity between theoretical predictions of the total rate coefficient of vinyl + 1,3-butadiene. The two sets of computed results by Cavallotti et al 20,21 and predictions of recent work by Xu et al 23 are more than an order of magnitude faster than those predicted here and earlier by Westmoreland et al 12 We note that the rate coefficient for the entrance channel computed by Cavallotti (private communications) used a 2-dimensional (2D) treatment of the hindered rotor that accounts for not only the rotation of the two moieties about the axis defining the forming bond but also one of the rocking motions in the transition state. Cavallotti et al employed the Unimol code originally developed by Gilbert and Smith.…”

Section: ■ Computational Methodscontrasting

confidence: 73%

“…For many flames it is thought to be the rate-limiting step. − Benzene is the prototypical first aromatic ring, although others such as toluene, styrene, phenylacetylene, indene, and naphthalene are certainly possible and have been considered in the literature. Several reactions that have received special attention over the last 30 years as potential sources of benzene in various flames are the following: (1) n -C 4 H 3 / n -C 4 H 5 + C 2 H 2 ; − (2) C 2 H 3 + 1,3-C 4 H 6 ; ,,,,− and (3) C 3 H 3 + C 3 H 3 . ,− Chemistry of five carbon rings (i.e., cyclopentadienyl, cyclopentadiene, and fulvene) is also thought to lead to larger aromatic rings. ,, With the exception of propargyl radical recombination, C 3 H 3 + C 3 H 3 , there is a dearth of direct experimental measurements of the reactions listed above.…”

Section: Introductionmentioning

confidence: 99%

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Kinetics and Products of Vinyl + 1,3-Butadiene, a Potential Route to Benzene

et al. 2015

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The reaction between vinyl radical, C2H3, and 1,3-butadiene, 1,3-C4H6, has long been recognized as a potential route to benzene, particularly in 1,3-butadiene flames, but the lack of reliable rate coefficients has hindered assessments of its true contribution. Using laser flash photolysis and visible laser absorbance (λ = 423.2 nm), we measured the overall rate coefficient for C2H3 + 1,3-C4H6, k1, at 297 K ≤ T ≤ 494 K and 4 ≤ P ≤ 100 Torr. k1 was in the high-pressure limit in this range and could be fit by the simple Arrhenius expression k1 = (1.1 ± 0.2) × 10(-12) cm(3) molecule(-1) s(-1) exp(-9.9 ± 0.6 kJ mol(-1)/RT). Using photoionization time-of-flight mass spectrometry, we also investigated the products formed. At T ≤ 494 K and P = 25 Torr, we found only C6H9 adduct species, while at 494 K ≤ T ≤ 700 K and P = 4 Torr, we observed ≤∼10% branching to cyclohexadiene in addition to C6H9. Quantum chemistry master-equation calculations using the modified strong collision model indicate that n-C6H9 is the dominant product at low temperature, consistent with our experimental results, and predict the rate coefficient and branching ratios at higher T where chemically activated channels become important. Predictions of k1 are in close agreement with our experimental results, allowing us to recommend the following modified Arrhenius expression in the high-pressure limit from 300 to 2000 K: k1 = 6.5 × 10(-20) cm(3) molecule(-1) s(-1) T(2.40) exp(-1.76 kJ mol(-1)/RT).

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Section: ■ Computational Methodscontrasting

confidence: 73%

Section: Introductionmentioning

confidence: 99%

Kinetics and Products of Vinyl + 1,3-Butadiene, a Potential Route to Benzene

et al. 2015

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“…These data were based on high pressure rate constants from the literature; thermochemical assumptions and quantum-RRK calculations had been then performed to calculate rate constants at 1 atm and 50 Torr. More recently, Cavallotti et al [46], in an ab initio study of the reactions of butadiene leading to soot formation, proposed a rate constant for the addition of C 2 H 3 to butadiene and the subsequent decompositions or cyclization reaction of the adduct. These values lead to a higher rate of formation of cyclohexene than that of Westmoreland et al [3] and confirm that this channel can play a role in these conditions.…”

Section: Discussionmentioning

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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“…47,48 The models suggest further that consecutive reactions of the phenyl radical with unsaturated hydrocarbons can form more complex structures, possibly bicyclic aromatic hydrocarbon molecules like indene (C 9 H 8 ) and naphthalene (C 10 H 8 ). [49][50][51][52] Although the propargyl radical represents the most studied RSFR due to its potential role in the formation of the first aromatic ring in hydrocarbon flames, its stability and hence unimolecular decomposition has been poorly understood so far. 42,44,48,[53][54][55][56][57][58][59][60][61][62][63][64][65] Here, the unimolecular decomposition of propargyl 66 has been suggested to form predominantly C 3 H 2 isomers cyclopropenylidene (c-C 3 H 2 ; X 1 A 1 ), propargylene (HCCCH; X 3 B), and vinylidene carbene (H 2 CCC; X 1 A 1 ) (Fig.…”

Section: Introductionmentioning

confidence: 99%

A crossed molecular beam study on the reaction of methylidyne radicals [CH(X²Π)] with acetylene [C₂H₂(X¹Σ_g⁺)]—competing C₃H₂+ H and C₃H + H₂channels

Maksyutenko

Zhang

et al. 2011

Phys. Chem. Chem. Phys.

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We carried out the crossed molecular beam reaction of ground state methylidyne radicals, CH(X(2)Π), with acetylene, C(2)H(2)(X(1)Σ(g)(+)), at a nominal collision energy of 16.8 kJ mol(-1). Under single collision conditions, we identified both the atomic and molecular hydrogen loss pathways forming C(3)H(2) and C(3)H isomers, respectively. A detailed analysis of the experimental data suggested the formation of c-C(3)H(2) (31.5 ± 5.0%), HCCCH/H(2)CCC (59.5 ± 5.0%), and l-HCCC (9.0 ± 2.0%). The reaction proceeded indirectly via complex formation and involved the unimolecular decomposition of long-lived propargyl radicals to form l-HCCC plus molecular hydrogen and HCCCH/H(2)CCC plus atomic hydrogen. The formation of c-C(3)H(2) was suggested to be produced via unimolecular decomposition of the cyclopropenyl radical, which in turn could be accessed via addition of the methylidyne radical to both carbon atoms of the acetylene molecule or after an initial addition to only one acetylenic carbon atom via ring closure. This investigation brings us closer to unraveling of the reaction of important combustion radicals-methylidyne-and the connected unimolecular decomposition of chemically activated propargyl radicals. This also links to the formation of C(3)H and C(3)H(2) in combustion flames and in the interstellar medium.

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A Quantum Chemistry Study of the Formation of Pah and Soot Precursors Through Butadiene Reactions

Cited by 12 publications

References 14 publications

Kinetics and Products of Vinyl + 1,3-Butadiene, a Potential Route to Benzene

Kinetics and Products of Vinyl + 1,3-Butadiene, a Potential Route to Benzene

Rich methane premixed laminar flames doped by light unsaturated hydrocarbons

A crossed molecular beam study on the reaction of methylidyne radicals [CH(X²Π)] with acetylene [C₂H₂(X¹Σ_g⁺)]—competing C₃H₂+ H and C₃H + H₂channels

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A Quantum Chemistry Study of the Formation of Pah and Soot Precursors Through Butadiene Reactions

Cited by 12 publications

References 14 publications

Kinetics and Products of Vinyl + 1,3-Butadiene, a Potential Route to Benzene

Kinetics and Products of Vinyl + 1,3-Butadiene, a Potential Route to Benzene

Rich methane premixed laminar flames doped by light unsaturated hydrocarbons

A crossed molecular beam study on the reaction of methylidyne radicals [CH(X2Π)] with acetylene [C2H2(X1Σg+)]—competing C3H2+ H and C3H + H2channels

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A crossed molecular beam study on the reaction of methylidyne radicals [CH(X²Π)] with acetylene [C₂H₂(X¹Σ_g⁺)]—competing C₃H₂+ H and C₃H + H₂channels