Selective identification of cyclopentaring-fused PAHs and side-substituted PAHs in a low pressure premixed sooting flame by photoelectron photoion coincidence spectroscopy

Abstract

<p>This work reports on the selective on line identification of polycyclic aromatic hydrocarbons (PAHs) formed in a low-pressure methane sooting flame, carried out using the double imaging Photoelectron Photoion Coincidence...</p>

Experimental study of the influence of hydrogen as a fuel additive on the formation of soot precursors and particles in atmospheric laminar premixed flames of methane

“…Although the mechanism of formation of nascent soot particles from PAHs precursors is still discussed in the community, a large number of studies [43,47,[64][65][66][67][68][69] mentioned that moderate sized PAHs as pyrene could play an important role in the nucleation process. More specifically, the formation of dimers of such PAHs has been suggested as a potential key step allowing the formation of nascent soot particles [47,[66][67][68][69][70][71][72][73]. However, because of the weak energy of the Van der Waals bonds characterizing dimers of PAHs, especially at flame temperature [74,75], this hypothesis has often been considered as a numerical tool for kinetic modelling rather than a real physical process actually involved in sooting flames.…”

“…In that context, Kholghy et al [72] recently suggested a model for the soot nucleation relying on the reversibility of the nucleation process [71,75] associated to the formation of homo and heterogeneous dimers of low molecular weight, stabilized by the formation of a covalent carbon-carbon bound between the two PAHs constituted the dimer. The formation of bonded dimers of moderate-sized PAHs, either by formation of direct covalent bonds or aliphatic bridges, is a current hot topic in the combustion community and has been the subject of different recent experimental and modeling works [68,72,73,[76][77][78][79][80][81]. From these papers, it appears that more and more studies support the idea of a crucial implication of moderate-sized PAHs in the nucleation step leading the formation of the very first particles in flames.…”

Photoelectron Photoion Coincidence Spectroscopy Provides Mechanistic Insights in Fuel Synthesis and Conversion

“…The cooling process can be improved by microprobe sampling. In 2020, Mercier et al presented highly resolved TPE spectra of PAH measured with the VUV-PEPICO instrument at SOLEIL . With this development, the authors have substantially advanced the detection options for PAH in flames and show that PEPICO detection has a high potential for investigating the in situ mechanisms of soot and PAH formation in laboratory flames, however, at the expense of quenching reactive intermediates.…”

Polycyclic aromatic hydrocarbon growth in a benzene discharge explored by IR-UV action spectroscopy

“…13,14 Pyrolysis and crossed molecular beam studies have made major contributions towards understanding gas-phase formation pathways of PAHs. [15][16][17] However, the complexity of the interconnected chemical pathways resulting in PAH formation and dissociation is still difficult to account for in astrochemical models. [18][19][20] This generally leads to an underestimation of aromatic species in the ISM 21,22 or in pyrolysis experiments.…”