Oxidation of lignin and cellulose, humification and coalification
Oxygen plays an important role in the first stages of the decomposition of organic substances derived from plant material. The decomposition and reformation of such organic matter as cellulose and lignin leads, through-humification and a sequence of metamorphic processes, to the formation of coal. Initially, oxidation reactions cause the formation of dark-colored humic acids, later under more anaerobic conditions, pressure and higher temperatures, polymerization occurs as the sediment becomes buried. Under these conditions phenolic compounds are more stable, also during the processes of decomposition phenolic substances are more resistant to microorganisms, and thus seem to accumulate. The humification process may be considered as the first step in coalification. It starts by rapid decomposition of the cellulose and by enzymatic degradation of the lignin of the rotting plant substance to form C/sub 6/-C/sub 3/ or C/sub 6/-C/sub 1/ compounds. These lose methoxyl groups and carboxyl groups and can form hydroquinones which may polymerize and combine, forming humic acids. Degradation may proceed also to aliphatic compounds. Most of the reactions seem to lead to benzoquinones which dimerize and polymerize further, causing an increase in aromatization with age, and under more anaerobic conditions later during coalification. When conditions become anaerobic, melanoidin and glucosamin compounds form and nitrogen fixation occurs. This explains the presence of about 1 to 3.5 percent nitrogen in humic acid concentrates, lignin, lignite, subbituminous and bituminous coal. The fixation of nitrogen also results in further reduction of carbon in humic substance during the later stages of humification. Further coalification of buried humified strata of decomposed organic material causes reduction as the methoxyl and oxygen group content decreases, and CO and CO/sub 2/ gases and H/sub 2/O evolve and gradual dehydration occurs.
- Research Organization:
- North Dakota State Univ., Fargo (USA); California Univ., Irvine (USA)
- Sponsoring Organization:
- US Energy Research and Development Administration (ERDA)
- DOE Contract Number:
- EY-76-S-02-2898; EY-76-S-03-0034
- OSTI ID:
- 7258299
- Report Number(s):
- COO-2898-2
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
CELLULOSE
OXIDATION
COAL
ORIGIN
LIGNIN
BACTERIA
BIODEGRADATION
COALIFICATION
ENZYMES
HUMIC ACIDS
CARBOHYDRATES
CARBONACEOUS MATERIALS
CHEMICAL REACTIONS
DECOMPOSITION
ENERGY SOURCES
FOSSIL FUELS
FUELS
MICROORGANISMS
ORGANIC ACIDS
ORGANIC COMPOUNDS
POLYSACCHARIDES
SACCHARIDES
011000* - Coal
Lignite
& Peat- Reserves
Geology
& Exploration