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Issue 20, 2010
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Micro-FTIR study of soot chemical composition—evidence of aliphatic hydrocarbons on nascent soot surfaces

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Abstract

Previous studies suggest that soot formed in premixed flat flames can contain a substantial amount of aliphatic compounds. Presence of these compounds may affect the kinetics of soot mass growth and oxidation in a way that is currently not understood. Using an infrared spectrometer coupled to a microscope (micro-FTIR), we examined the composition of soot sampled from a set of ethyleneargonoxygen flames recently characterized (A. D. Abid, et al. Combust. Flame, 2008, 154, 775–788), all with an equivalence ratio ϕ = 2.07 but varying in maximum flame temperatures. Soot was sampled at three distances above the burner surface using a probe sampling technique and deposited on silicon nitride thin film substrates using a cascade impactor. Spectra were taken and analyses performed for samples collected on the lowest five impactor stages with the cut-off sizes of D50 = 10, 18, 32, 56 and 100 nm. The micro-FTIR spectra revealed the presence of aliphatic C–H, aromatic C–H and various oxygenated functional groups, including carbonyl (C[double bond, length as m-dash]O), C–O–C and C–OH groups. Spectral analyses were made to examine variations of these functional groups with flame temperature, sampling position and particle size. Results indicate that increases in flame temperature leads to higher contents of non-aromatic functionalities. Functional group concentrations were found to be ordered as follows: [C[double bond, length as m-dash]O] < [C–O] < [aliphatic C–H]. Aliphatic C–H was found to exist in significant quantities, with very little oxygenated groups present. The ratio of these chemical functionalities to aromatic C–H remains constant for particle sizes spanning 10–100 nm. The results confirm a previous experimental finding: a significant amount of aliphatic compounds is present in nascent soot formed in the flames studied, especially towards larger distances above the burner surface.

Graphical abstract: Micro-FTIR study of soot chemical composition—evidence of aliphatic hydrocarbons on nascent soot surfaces

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Publication details

The article was received on 19 Nov 2009, accepted on 16 Feb 2010 and first published on 19 Mar 2010


Article type: Paper
DOI: 10.1039/B924344E
Citation: Phys. Chem. Chem. Phys., 2010,12, 5206-5218
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    Micro-FTIR study of soot chemical composition—evidence of aliphatic hydrocarbons on nascent soot surfaces

    J. P. Cain, P. L. Gassman, H. Wang and A. Laskin, Phys. Chem. Chem. Phys., 2010, 12, 5206
    DOI: 10.1039/B924344E

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