Theoretical study on the mechanism and kinetics of the oxidation of allyl radical with atomic and molecular oxygen

Alarcon, Juan F.; Ajo, Sergio; Morozov, Alexander N.; Mebel, Alexander M.

doi:10.1016/j.combustflame.2022.112388

Cited by 5 publications

(3 citation statements)

References 63 publications

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“…Enols, for instance, are likely produced via partial hydrocarbon oxidation on the catalyst surface in ODHP, followed by desorption into the gas phase. In the gas phase, the allyl + O 2 reaction affords formaldehyde (observed in Figure S4) and the H 2 C–C(O)H radical, in an exothermic reaction (−2.75 eV) after an entrance barrier of 0.55 eV, which is likely reduced in the presence of BN. The H 2 C–C(O)H radical can either be dehydrogenated to yield ketene or hydrogenated to vinyl alcohol or acetaldehyde ( m / z 44, Figures S5, S8), which were all observed in this study.…”

Section: Resultsmentioning

confidence: 99%

Unraveling Radical and Oxygenate Routes in the Oxidative Dehydrogenation of Propane over Boron Nitride

Zhang

Tian

et al. 2023

J. Am. Chem. Soc.

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Oxidative dehydrogenation of propane (ODHP) is an emerging technology to meet the global propylene demand with boron nitride (BN) catalysts likely to play a pivotal role. It is widely accepted that gas-phase chemistry plays a fundamental role in the BN-catalyzed ODHP. However, the mechanism remains elusive because short-lived intermediates are difficult to capture. We detect short-lived free radicals (CH 3• , C 3 H 5 • ) and reactive oxygenates, C 2−4 ketenes and C 2−3 enols, in ODHP over BN by operando synchrotron photoelectron photoion coincidence spectroscopy. In addition to a surface-catalyzed channel, we identify a gas-phase H-acceptor radical-and Hdonor oxygenate-driven route, leading to olefin production. In this route, partially oxidized enols propagate into the gas phase, followed by dehydrogenation (and methylation) to form ketenes and finally yield olefins by decarbonylation. Quantum chemical calculations predict the >BO dangling site to be the source of free radicals in the process. More importantly, the easy desorption of oxygenates from the catalyst surface is key to prevent deep oxidation to CO 2 .

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Section: Resultsmentioning

confidence: 99%

Unraveling Radical and Oxygenate Routes in the Oxidative Dehydrogenation of Propane over Boron Nitride

Zhang

Tian

et al. 2023

J. Am. Chem. Soc.

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“…Naphthalene can be formed through many different pathways , verified both by experiments and theory and included in the current kinetic models of the PAH growth, such as hydrogen abstraction–acetylene addition (HACA) − and hydrogen abstraction–vinylacetylene addition (HAVA) , commencing from benzene, self-recombination of the cyclopentadienyl radical (C 5 H 5 · + C 5 H 5 · ), − recombination of benzyl and propargyl radicals (C 7 H 7 · + C 3 H 3 · ) , and of indenyl with methyl (C 9 H 7 · + CH 3 · ). , Still, the models tend to perform poorly and inconsistently in regard to naphthalene predictions. For instance, C3MechV3.3 and CRECK kinetic models tend to underpredict naphthalene formation in ethylene, acetylene, and benzene premixed flames, especially at lower pressures, , as well as in flow reactor experiments of cyclopentadiene and benzene oxidation. Conversely, naphthalene formation in counterflow diffusion flames of various fuels such as acetylene, ethylene, and butene is generally overpredicted also in other literature models .…”

Section: Introductionmentioning

confidence: 99%

“…30,31 Still, the models tend to perform poorly and inconsistently in regard to naphthalene predictions. For instance, C3MechV3.3 and CRECK kinetic models tend to underpredict naphthalene formation in ethylene, acetylene, and benzene premixed flames, especially at lower pressures, 32,33 as well as in flow reactor experiments of cyclopentadiene and benzene oxidation. Conversely, naphthalene formation in counterflow diffusion flames of various fuels such as acetylene, ethylene, and butene is generally overpredicted also in other literature models.…”

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confidence: 99%

Fulvenallenyl Radical (C₇H₅^·)-Mediated Gas-Phase Synthesis of Bicyclic Aromatic C₁₀H₈ Isomers: Can Fulvenallenyl Efficiently React with Closed-Shell Hydrocarbons?

Mebel,

Li,

Pratali Maffei

et al. 2024

J. Phys. Chem. A

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To understand the reactivity of resonantly stabilized radicals, often found in relevant concentrations in gaseous environments, it is important to determine their main reaction pathways. Here, it is investigated whether the fulvenallenyl radical (C 7 H 5• ) reacts preferentially with closed-shell molecules or radicals. Electronic structure calculations on the C 10 H 9 potential energy surface accessed by the reactions of C 7 H 5• with methylacetylene (CH 3 CCH) and allene (H 2 CCCH 2 ) were combined with RRKM-ME calculations of temperature-and pressure-dependent rate constants using the automated EStokTP software suite and kinetic modeling to assess the reactivity of C 7 H 5 • with closed-shell unsaturated hydrocarbons. Experimentally, the reactions were attempted in a chemical microreactor heated to 998 ± 10 K by preparing fulvenallenyl radicals via pyrolysis of trichloromethylbenzene (C 7 H 5 Cl 3 ) and seeding the radicals in methylacetylene or allene carrier gas, with product identification by means of photoionization mass spectrometry. The measured photoionization efficiency curve of m/z = 128 was assigned to a linear combination of the reference curves of two C 10 H 8 isomers, azulene (minor) and naphthalene (major), presumably resulting from the C 7 H 5• plus C 3 H 4 reactions. However, the calculations demonstrated that these reactions are too slow, and kinetic modeling of processes in the reactor allowed us to conclude that the observation of naphthalene and azulene is due to the C 7 H 5• plus C 3 H 3 • reaction, where propargyl is produced by direct hydrogen atom abstraction by chlorine (Cl) atoms from allene or methylacetylene and Cl stem from the pyrolysis of C 7 H 5 Cl 3 . Modeling results under the copyrolysis conditions of toluene and methylacetylene in high-temperature shock tube experiments confirmed the prevalence of the fulvenallenyl reaction with propargyl over its reactions with C 3 H 4 even when the concentrations of allene and methylacetylene largely exceed that of propargyl. Overall, the reactions of fulvenallenyl with both allene and methylacetylene were found to be noncompetitive in the formation of naphthalene and azulene thus attesting the inefficiency of the fulvenallenyl radical reactions with the prototype closed-shell hydrocarbon species. In the meantime, the new reaction pathways revealed, including Hassisted isomerizations between C 10 H 8 isomers and decomposition reactions of various C 10 H 9 isomers, emerge as relevant and are recommended for inclusion in combustion kinetic models for naphthalene formation.

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High-temperature thermal decomposition of triphenyl phosphate vapor in an inert medium: Flow reactor pyrolysis, quantum chemical calculations, and kinetic modeling

Шмаков

Коробейничев

Mebel

et al. 2023

Combustion and Flame

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Theoretical study on the mechanism and kinetics of the oxidation of allyl radical with atomic and molecular oxygen

Cited by 5 publications

References 63 publications

Unraveling Radical and Oxygenate Routes in the Oxidative Dehydrogenation of Propane over Boron Nitride

Unraveling Radical and Oxygenate Routes in the Oxidative Dehydrogenation of Propane over Boron Nitride

Fulvenallenyl Radical (C₇H₅^·)-Mediated Gas-Phase Synthesis of Bicyclic Aromatic C₁₀H₈ Isomers: Can Fulvenallenyl Efficiently React with Closed-Shell Hydrocarbons?

High-temperature thermal decomposition of triphenyl phosphate vapor in an inert medium: Flow reactor pyrolysis, quantum chemical calculations, and kinetic modeling

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Theoretical study on the mechanism and kinetics of the oxidation of allyl radical with atomic and molecular oxygen

Cited by 5 publications

References 63 publications

Unraveling Radical and Oxygenate Routes in the Oxidative Dehydrogenation of Propane over Boron Nitride

Unraveling Radical and Oxygenate Routes in the Oxidative Dehydrogenation of Propane over Boron Nitride

Fulvenallenyl Radical (C7H5·)-Mediated Gas-Phase Synthesis of Bicyclic Aromatic C10H8 Isomers: Can Fulvenallenyl Efficiently React with Closed-Shell Hydrocarbons?

High-temperature thermal decomposition of triphenyl phosphate vapor in an inert medium: Flow reactor pyrolysis, quantum chemical calculations, and kinetic modeling

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Fulvenallenyl Radical (C₇H₅^·)-Mediated Gas-Phase Synthesis of Bicyclic Aromatic C₁₀H₈ Isomers: Can Fulvenallenyl Efficiently React with Closed-Shell Hydrocarbons?