High-sensitivity detection of polycyclic aromatic hydrocarbons adsorbed onto soot particles using laser desorption/laser ionization/time-of-flight mass spectrometry: An approach to studying the soot inception process in low-pressure flames

Journal Article · Tue Feb 15 00:00:00 EST 2011 · Combustion and Flame

DOI:https://doi.org/10.1016/J.COMBUSTFLAME.2010.08.012· OSTI ID:21401354

Faccinetto, Alessandro ^[1]; Desgroux, Pascale; Therssen, Eric ^[1]; Ziskind, Michael; Focsa, Cristian ^[2]

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1. Laboratoire de Physico-Chimie des Processus de Combustion et de l'Atmosphere (PC2A), UMR CNRS 8522 (France)
2. Laboratoire de Physique des Lasers, Atomes et Molecules (PhLAM), UMR CNRS 8523, Centre d'Etudes et de Recherches Lasers et Applications, Universite de Lille 1, 59655 Villeneuve d'Ascq Cedex (France)

Species adsorbed at the surfaces of soot particles sampled at different locations in a low-pressure methane flame have been analyzed. The analysis method is laser desorption/laser ionization/time-of-flight mass spectrometry (LD/LI/TOF-MS) applied to soot particles deposited on a filter after probe extraction in the flame. In order to fully characterize the experimental apparatus, a strategy of systematic investigations has been adopted, beginning with the study of less complex systems constituted by model soot (standard polycyclic aromatic hydrocarbons, PAHs, adsorbed on black carbon), and then natural soot sampled from a literature reference ethylene flame. This characterization allowed a good understanding of the analytical response of PAHs to the desorption and ionization processes and the definition of the optimal experimental conditions. The soot PAH content was then investigated on a low-pressure methane/oxygen/nitrogen premixed flat flame ({phi} = 2.32) as a function of the sampling height above the burner (HAB). The obtained mass spectra are reproducible, fragment-free, well resolved in the analyzed m/z range and they are characterized by an excellent signal-to-noise ratio. They all feature regular peak sequences, where each signal peak has been assigned to the most stable high-temperature-formed PAHs. The structure of the mass spectra depends on the sampling HAB into the flame, i.e., on the reaction time. An original contribution to the data interpretation comes from the development of a new sampling method that makes it possible to infer hypotheses about the PAH partition between the gas phase and the soot particles. This method highlights the presence of high-mass PAHs in the soot nucleation zone, and it suggests the importance of heterogeneous reactions occurring between flame PAHs and soot particles. (author)

• OSTI ID: 21401354
• Journal Information: Combustion and Flame, Vol. 158, Issue 2; Other Information: Elsevier Ltd. All rights reserved; ISSN 0010-2180
• Country of Publication: United States
• Language: English

Related Subjects

37 INORGANIC
ORGANIC
PHYSICAL AND ANALYTICAL CHEMISTRY
POLYCYCLIC AROMATIC HYDROCARBONS
MASS SPECTROSCOPY
SOOT
DESORPTION
METHANE
FLAMES
LASERS
MASS SPECTRA
ETHYLENE
IONIZATION
TIME-OF-FLIGHT METHOD
TEMPERATURE RANGE 1000-4000 K
CARBON
NITROGEN
OXYGEN
SAMPLING
SIGNAL-TO-NOISE RATIO
DETECTION
HEIGHT
PEAKS
BURNERS
HYPOTHESIS
PRESSURE RANGE KILO PA
NUCLEATION
PARTITION
ZONES
Premixed flames