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Can pyrolysis-GC/MS be used to estimate the degree of thermal alteration of black carbon?

Abstract : Very little is known about the macromolecular properties of biomass combustion residues referred to as black carbon (BC). Pyrolysis-gas chromatography-mass spectrometry (Py-GC/MS) was performed on: (i) peat from Spain at 400-1200 degrees C to investigate the effect of charring on pyrolysis fingerprint and (ii) natural charcoal from Laos in order to link molecular information to published chemical and reactivity parameters. Confirming earlier Py-GC/MS studies, the BC in the artificially charred peat and the natural charcoal produced predominantly benzene, toluene, C-2-benzenes, PAHs and benzonitriles. Furthermore, some charcoal samples produced significant amounts of phenols, methoxyphenols, carbohydrate markers, n-alkanes and n-alkenes upon pyrolysis, reflecting non-charred and weakly charred biomass. A series of pyrolysis product ratios related to the degree of dealkylation of the pyrolysis products (benzene/toluene, naphthalene/C-1-naphthalenes, C-1-naphthalenes/C-2-naphthalenes, benzofuran/C-1-benzofurans and benzonitrile/C-1-benzonitrile) increased with increasing artificial charring (peat) and, for the natural charcoal, these ratios were in accordance with established chemical and reactivity parameters related to charring intensity from other methods: proportion of aromatic C obtained from solid state 13 C nuclear magnetic resonance spectroscopy (NMR), the proportion of charred material as estimated from NMR in conjunction with a molecular mixing model (NMR-MMM) and the resistance to acid dichromate oxidation. The alkyl side chains of aromatic pyrolysis products are probably inherited from short chain aliphatic C chains that cross link the predominantly aromatic building blocks of BC, and these linkages seem to disappear with increasing charring intensity. Thus, the degree of thermal alteration of BC can be discerned from the pyrolysis fragmentation pattern.
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https://hal-bioemco.ccsd.cnrs.fr/bioemco-00450914
Contributor : Liliane Guerrier <>
Submitted on : Wednesday, January 27, 2010 - 4:14:00 PM
Last modification on : Sunday, May 31, 2020 - 7:31:27 AM

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J. Kaal, Cornelia Rumpel. Can pyrolysis-GC/MS be used to estimate the degree of thermal alteration of black carbon?. Organic Geochemistry, Elsevier, 2009, 40, pp.1179-1187. ⟨10.1016/j.orggeochem.2009.09.002⟩. ⟨bioemco-00450914⟩

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