Use of stable carbon isotope compositions of pyrolytically derived methane as maturity indices for carbonaceous materials
Nineteen coals of varying ranks and twelve organic-solvent-extracted shales of different ages and maturities were subjected to a long-term, closed system, isothermal (500/sup 0/C) pyrolysis procedure until no additional methane or carbon oxide gases were generated. Three significant trends were observed: (1) for all of the samples, the stable carbon isotope difference between the total accumulated methane and parent carbon was linearly correlated with yield of methane with r = 0.88; (2) for a series of thirteen model compounds, two lipid-free shales and twelve coals, the H/C ratio of each was linearly correlated with the yield of methane with r = 0.93; (3) for a series of eleven coals samples, the O/C ratio of each was linearly correlated with the yield of carbon oxides with r = 0.97. The experimental relationships described above indicate that a simple pyrolysis procedure and measurements of the amounts of generated CH/sub 4/, CO/sub 2/, and CO relative to the carbon content of the sample and the stable isotopic compositions of the methane and parent organic carbon give: (a) an index of the maturity and (b) values which are directly related to the H/C and O/C ratios of the carbonaceous materials. 7 figures, 5 tables.
- Research Organization:
- Texas A and M Univ., College Station
- OSTI ID:
- 5699595
- Journal Information:
- Geochim. Cosmochim. Acta; (United States), Vol. 43:12
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
10 SYNTHETIC FUELS
COAL
ISOTOPE RATIO
PYROLYSIS
METHANE
OIL SHALES
CARBON
CARBON DIOXIDE
CARBON ISOTOPES
CARBON MONOXIDE
CARBONACEOUS MATERIALS
HIGH TEMPERATURE
ISOTHERMAL PROCESSES
MATURATION
ORGANIC SOLVENTS
OXYGEN
SYNTHESIS
ALKANES
BITUMINOUS MATERIALS
CARBON COMPOUNDS
CARBON OXIDES
CHALCOGENIDES
CHEMICAL REACTIONS
CRYOGENIC FLUIDS
DECOMPOSITION
ELEMENTS
ENERGY SOURCES
FLUIDS
FOSSIL FUELS
FUELS
HYDROCARBONS
NONMETALS
ORGANIC COMPOUNDS
OXIDES
OXYGEN COMPOUNDS
SOLVENTS
THERMOCHEMICAL PROCESSES
010406* - Coal & Coal Products- Pyrolysis & Cracking- (-1987)
090121 - Hydrocarbon Fuels- Chemical Synthesis- (1976-1989)