Nucleation of soot: experimental assessment of the role of polycyclic aromatic hydrocarbon (PAH) dimers
| Autor: | Nils Hansen, Musahid Ahmed, Brian A. Adamson, Scott A. Skeen |
|---|---|
| Rok vydání: | 2020 |
| Předmět: |
chemistry.chemical_classification
Chemical Physics 010304 chemical physics Radical Nucleation Analytical chemistry Polycyclic aromatic hydrocarbon 02 engineering and technology 021001 nanoscience & nanotechnology medicine.disease_cause 01 natural sciences Soot Adiabatic flame temperature chemistry.chemical_compound fluids and secretions Monomer chemistry Theoretical and Computational Chemistry 0103 physical sciences medicine Mass spectrum Pyrene Physical and Theoretical Chemistry 0210 nano-technology Physical Chemistry (incl. Structural) |
| Zdroj: | Zeitschrift für Physikalische Chemie, vol 234, iss 7-9 Zeitschrift fur Physikalische Chemie, vol 234, iss 7-9 |
| Popis: | 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. |
| Databáze: | OpenAIRE |
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