Study on the contribution of different molecular weight species to the absorption UV-Visible spectra of flame-formed carbon species

作者：Russo Carmela^*; Stanzione Fernando; Ciajolo Anna; Tregrossi Antonio

来源：Proceedings of the Combustion Institute, 2013, 34(2): 3661-3668.

DOI：10.1016/j.proci.2012.06.097

• Diagnostics
• PAH
• Particulate matter
• UV-Visible spectroscopy

A reconstruction method of UV-Visible spectra, recently developed for discriminating the contribution of different molecular weight (MW) species to the spectral properties of carbonaceous species formed in a premixed ethylene flame, was applied to a benzene flame. The reliability and sensitivity of the technique in detecting specific structural features of the carbonaceous species was demonstrated. %26lt;br%26gt;The flame-formed carbon species were deposited on quartz plates inserted in the soot formation region of a premixed fuel-rich benzene flame. The dichloromethane-soluble (DCM-soluble) and dry soot fractions were separated in a very wide MW range, from 200 to 1E11 u, by Size Exclusion Chromatography (SEC) coupled with on-line UV-Visible spectroscopy. The optical band gap (E-g) and the UV peak position of each MW-segregated fraction were evaluated by means of a spectral reconstruction procedure, to get details on the carbon network structure in terms of sp(2) and sp(3) sites and size and stacking of the aromatic units. Moreover, the MW-segregated fractions of the species soluble in DCM were also analyzed by fluorescence emission spectroscopy and by atmospheric pressure laser desorption ionization-mass spectrometry for determining their aromatic character. %26lt;br%26gt;The output of the spectral reconstruction procedure provided insights in the chemical structure and evolution of carbonaceous species from Polycyclic Aromatic Hydrocarbons (PAH) to soot nuclei and finally to soot aggregates. The comparison with data obtained in a premixed ethylene flame burning in similar temperature conditions showed some structural differences in flame-formed carbonaceous species due to the effect of the different chemical environment in which soot precursor are formed.

• 出版日期2013