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Open Access item Characterization of humic acids from low-rank coals by 13C-NMR and pyrolysis-methylation. Formation of benzenecarboxylic acid moieties during the coalification process

Authors:Río Andrade, José Carlos del
González-Vila, Francisco Javier
Martín Martínez, Francisco
Verdejo Robles, Trinidad
Keywords:Peat, Lignite, Coalification, Pyrolysis, Tetramethylammonium hydroxide (TMAH), CP/MAS 13C-NMR, Benzenecarboxylic acids
Issue Date:1994
Citation:Organic Geochemistry 22(6): 885-891 (1994)
Abstract:Humic acid (HA) fractions isolated from a peat and lignite deposit were studied by CP/MAS 13C-NMR and pyrolysis-methylation. Loss of carbohydrates, removal of methoxyls and formation of catechols during the coalification process was evident. Pyrolysis-methylation released a great variety of components, the lignin-derived monomers being the most prominent. A very striking feature was the release of benzenecarboxylic moieties after pyrolysis-methylation which have not been observed previously by pyrolytic techniques. These moieties were released in higher amounts from the lignite HA, suggesting that the content in carboxylic groups increase with coalification, at least up to the lignite stage. Oxidation of the C-3 side chain of the lignin structure would produce these benzenecarboxylic acids and benzylic ketones.
Description:Instituto de Recursos Naturales y Agrobiologia de Sevilla, C.S.I.C., P.O. Box 1052, 41080-Seville, Spain; E-mail address: delrio@irnase.csic.es
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