Carbonaceous Nanoparticle Molecular Inception from Radical Addition and van der Waals Coagulation of Polycyclic Aromatic Hydrocarbon-Based Systems. A Theoretical Study

Giordana, Anna; Maranzana, Andrea; Tonachini, Glauco

doi:10.1021/jp2010698

Cited by 27 publications

(18 citation statements)

References 108 publications

(165 reference statements)

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“…This would require a full kinetic mechanism considering both the formation and fragmentation routes for both pathways. Both the aromatic and aliphatically bonded complexes have been shown to form bonds of sufficient energy to withstand flame temperatures, ,, however, both will be subject to radical-induced fragmentation to varying degrees. Examples of this are hydrogen abstraction from aliphatics leading to β-scission that leads to the rapid fragmentation of aliphatic fuels as well as hydrogen addition to polyynes leading also to radical-induced fragmentation that inhibits growth of polyynes to <20 carbon atoms in size. , An example of this could be hydrogen addition to a (Ai) – (Ai) crosslink providing the (Ai) – (E) crosslink leading to a significant decrease in bond energy.…”

Section: Resultsmentioning

confidence: 99%

Reactivity of Polycyclic Aromatic Hydrocarbon Soot Precursors: Implications of Localized π-Radicals on Rim-Based Pentagonal Rings

Martin

Hou²,

Menon

et al. 2019

J. Phys. Chem. C

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This paper presents a systematic study of the reactivity of polycyclic aromatic hydrocarbons (PAH), identifying crosslinks that permit the combination of physical π-stacking interactions and covalent bonding. Hybrid density functional theory was used to identify the location of reactive sites on PAHs using the average local ionization potential. The bond energies formed between these various reactive sites were then computed. σ-Radicals were found to be the most reactive, forming bonds with other radicals and some reactive closed shell edge types. Partially saturated rim-based pentagonal rings were found to form localized π-radicals with high reactivity. This site, in addition to resonantly stabilized π-radicals, was found to be capable of bonding and stacking, which is explored for a variety of larger species. Localized π-radicals on rim-based pentagonal rings, in particular, were found to form strongly bound stacked complexes, indicating a potentially important role in soot formation.

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Section: Resultsmentioning

confidence: 99%

Reactivity of Polycyclic Aromatic Hydrocarbon Soot Precursors: Implications of Localized π-Radicals on Rim-Based Pentagonal Rings

Martin

Hou²,

Menon

et al. 2019

J. Phys. Chem. C

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“…[30][31][32] They added a chemical bond formation term that describes the formation of chemical bonds between PAHs and thus the scientific discussion currently shifts towards aliphatically bridged PAHs. 28,[33][34] These hypothesized compounds have only recently been identified in flame-sampling tandem mass spectrometry experiments. 35 In the same work, aliphatically substituted PAHs were identified, which might be of significance for particle inception as Violi and coworkers have shown that their dimers are more likely to survive elevated flame temperatures.…”

Section: Introductionmentioning

confidence: 99%

Nucleation of soot: experimental assessment of the role of polycyclic aromatic hydrocarbon (PAH) dimers

Adamson

Skeen

Ahmed

et al. 2020

Zeitschrift Für Physikalische Chemie

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The irreversible dimerization of polycyclic aromatic hydrocarbons (PAHs) – typically pyrene (C16H10) dimerization – is widely used in combustion chemistry models to describe the soot particle inception step. This paper concerns itself with the detection and identification of dimers of flame-synthesized PAH radicals and closed-shell molecules and an experimental assessment of the role of these PAH dimers for the nucleation of soot. To this end, flame-generated species were extracted from an inverse co-flow flame of ethylene at atmospheric pressure and immediately diluted with excess nitrogen before the mixture was analyzed using flame-sampling tandem mass spectrometry with collision-induced fragmentation. Signal at m/z = 404.157 (C32H20) and m/z = 452.157 (C36H20) were detected and identified as dimers of closed-shell C16H10 and C18H10 monomers, respectively. A complex between a C13H9 radical and a C24H12 closed-shell PAH was observed at m/z = 465.164 (C37H21). However, a rigorous analysis of the flame-sampled mass spectra as a function of the dilution ratio, defined as the ratio of the flow rates of the diluent nitrogen to the sampled gases, indicates that the observed dimers are not flame-born, but are produced in the sampling line. In agreement with theoretical considerations, this paper provides experimental evidence that pyrene dimers cannot be a key intermediate in particle inception at elevated flame temperatures.

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“…The particular reaction conditions in terms of molecular fuel structure, temperature, pressure, and other variables affect the internal nanostructure, chemical composition, mobility, and reactivity of soot particles [244] , [245] , [246] , [247] , [248] , [249] , which may be different in technical devices from laboratory reactors and flames. Attempts to link between PAHs, high-molecular-weight carbon structures, and initial particles has motivated theoretical work [199 , 250] as well as experimental approaches including in-situ LII [251] , [252] , [253] , probe-sampling tandem mass spectrometry (MS-MS) [254] , and ex-situ microscopy [207 , 252 , [255] , [256] , [257] , [258] to image carbon structures and particles while considering also probe sampling effects [259] .…”

Section: Selected Combustion Chemistry Advances – Overview and Recentmentioning

confidence: 99%

Combustion in the future: The importance of chemistry

Kohse‐Höinghaus

2021

Proceedings of the Combustion Institute

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Combustion involves chemical reactions that are often highly exothermic. Combustion systems utilize the energy of chemical compounds released during this reactive process for transportation, to generate electric power, or to provide heat for various applications. Chemistry and combustion are interlinked in several ways. The outcome of a combustion process in terms of its energy and material balance, regarding the delivery of useful work as well as the generation of harmful emissions, depends sensitively on the molecular nature of the respective fuel. The design of efficient, low-emission combustion processes in compliance with air quality and climate goals suggests a closer inspection of the molecular properties and reactions of conventional, bio-derived, and synthetic fuels. Information about flammability, reaction intensity, and potentially hazardous combustion by-products is important also for safety considerations. Moreover, some of the compounds that serve as fuels can assume important roles in chemical energy storage and conversion. Combustion processes can furthermore be used to synthesize materials with attractive properties. A systematic understanding of the combustion behavior thus demands chemical knowledge. Desirable information includes properties of the thermodynamic states before and after the combustion reactions and relevant details about the dynamic processes that occur during the reactive transformations from the fuel and oxidizer to the products under the given boundary conditions. Combustion systems can be described, tailored, and improved by taking chemical knowledge into account. Combining theory, experiment, model development, simulation, and a systematic analysis of uncertainties enables qualitative or even quantitative predictions for many combustion situations of practical relevance. This article can highlight only a few of the numerous investigations on chemical processes for combustion and combustion-related science and applications, with a main focus on gas-phase reaction systems. It attempts to provide a snapshot of recent progress and a guide to exciting opportunities that drive such research beyond fossil combustion.

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Carbonaceous Nanoparticle Molecular Inception from Radical Addition and van der Waals Coagulation of Polycyclic Aromatic Hydrocarbon-Based Systems. A Theoretical Study

Cited by 27 publications

References 108 publications

Reactivity of Polycyclic Aromatic Hydrocarbon Soot Precursors: Implications of Localized π-Radicals on Rim-Based Pentagonal Rings

Reactivity of Polycyclic Aromatic Hydrocarbon Soot Precursors: Implications of Localized π-Radicals on Rim-Based Pentagonal Rings

Nucleation of soot: experimental assessment of the role of polycyclic aromatic hydrocarbon (PAH) dimers

Combustion in the future: The importance of chemistry

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