Kerogen Chemistry 9. Removal of Kerogen Radicals and Their Role in Kerogen Anhydride Decomposition

Larsen, John W.; Ashida, Ryuichi; Painter, Paul C.; Doetschman, David C.

doi:10.1021/ef050368n

Cited by 5 publications

(4 citation statements)

References 21 publications

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“…Previous studies characterized the structure and composition of kerogen through thermogravimetry, Fourier transform infrared (FTIR) spectroscopy, nuclear magnetic resonance (NMR) spectroscopy, pyrolysis gas chromatography–mass spectrometry (Py-GC/MS), and X-ray diffraction. − However, the molecular structure of oil shale kerogen remains to be completely described because of its complex composition. In addition, kerogen from different sources considerably varies in constitution and construction, and these factors complicate the analysis of the pyrolysis process.…”

Section: Introductionmentioning

confidence: 99%

Characteristics of Thermal Bitumen Structure as the Pyrolysis Intermediate of Longkou Oil Shale

Jian

et al. 2017

Energy Fuels

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The effects of pyrolysis temperature on the structure of thermal bitumen as the pyrolysis intermediate of Longkou oil shale are investigated through electron paramagnetic resonance spectroscopy, Fourier transform infrared (FTIR) spectroscopy, nuclear magnetic resonance (NMR) spectroscopy, gas chromatography–mass spectrometry (GC-MS), and X-ray photoelectron spectroscopy (XPS). Results indicate that the free radical concentration of thermal bitumen increases at a maximum temperature of 410 °C and then decreases between 410 and 450 °C. Moreover, the g factors of thermal bitumen are slightly higher than 2 and decrease with increasing temperature because of the aromatization of saturates and decarboxylation. FTIR analysis indicates that decarboxylation is completed before the temperature reaches 370 °C. NMR analysis shows that aliphatic and aromatic compounds comprise more than 80% and 15–16% thermal bitumen, respectively. During pyrolysis, the fraction of aliphatic compounds, branched alkane, and the average methylene chain length decrease because of secondary cracking, and the C–C bond at the branch chain is easily cracked into gas and light oil.

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Section: Introductionmentioning

confidence: 99%

Characteristics of Thermal Bitumen Structure as the Pyrolysis Intermediate of Longkou Oil Shale

Jian

et al. 2017

Energy Fuels

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“…The evolution of N g with kerogen maturation has been discussed extensively (Morishima and Matsubayash, 1978;Marchand and Conard, 1980;Aizenshtat et al, 1986;Seehra et al, 1986;Fowler et al, 1987;Bakr et al, 1991;McTavish, 2003;Larsen et al, 2005Larsen et al, , 2006Lewan et al, 2006). The different evolutions of N g with vitrinite reflectance between three kerogen types are shown in Figure 1.…”

Section: Resultsmentioning

confidence: 97%

“…Since then, many ESR studies have documented the structure, maturation and reactivity of carbonaceous materials, such as coal, petroleum and kerogen (Retcofsky et al, 1968;Durand et al, 1977;Marchand and Conard, 1980;Tissot and Welte, 1984;Larter, 1988;Bakr et al, 1991;Trudy et al, 1995; Diaz et al, 2000;Bandara et al, 2005;Dick et al, 2005;Walters et al, 2007;Pancost et al, 2008;Tiem et al, 2008). The structure of kerogen was investigated by ESR method and attempts to correlate ESR parameters of kerogen with its maturation have been reported (Pusey, 1973;Marchand and Conard, 1980;Bakr et al, 1988;McTavish, 2003;Larsen et al, 2005Larsen et al, , 2006Lewan et al, 2006;Sun et al, 2006). Free radical concentrations in kerogen increase with maturity.…”

mentioning

confidence: 99%

Temperature and Time Effects on Free Radical Concentration in Organic Matter: Evidence from Laboratory Pyrolysis Experimental and Geological Samples

Qiu

et al. 2012

Energy Exploration & Exploitation

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The free radicals concentration (N g ) of organic matter evolves with the temperature, time, kerogen types and other factors for the individual kerogens. This paper focuses on the N g evolution of immature type I and II kerogens and a type III coal under the laboratory pyrolysis temperature and heating time. The experiments were carried out in a closed system pyrolysis at an isothermal reactor in the temperature range from 300 to 500°C over 30 to 480 minutes. A temperature time index (TTI) is applied and the TTI values were calculated in order to indicate the pyrolysis temperature and time at which the kerogen had experienced. Some equations were established to show the relationship between the TTI and N g of type I, II and III kerogens, based on the tested data from laboratory anhydrous pyrolysis experiments of three kerogen types and geological type I kerogen samples. However, the evolution of free radicals concentration with temperature and time shows some differentials between different types of kerogen samples. This paper also discusses the different TTI-N g relation of type I kerogen between laboratory pyrolysis experimental and geological samples, which are collected from core samples with depth interval of 1137 to 4090.6 m. The TTI-N g equation from pyrolysis experimental samples should be calibrated by the data from geological samples when the equation is to be extended to the geological timescales. As the free radical concentration in organic matter is strongly maturity dependent, the relationship between TTI-N g may prove to be a valuable method to study paleotemperature of sedimentary basins.Keywords: Free radicals, Vitrinite reflectance (R o ), Kerogen, Temperature Time Index (TTI), Thermal history, Pyrolysis experiment INTRODUCTIONFree radicals are units with an unpaired electron in organic matter. Kerogen, the portion of sedimentary organic matter not soluble in organic solvents, is believed to have analogous structures in which numerous aromatic rings form angularly conjunctive aromatic sheets, with substituents (such as paraffinic side chains) attached at the sheet margins (Tisssot and Welte, 1984). Thermal cracking of paraffinic chains from the kerogen molecules initially forms alkyl and kerogen free radicals (Wang and Chen, 1988). Smaller alkyl radicals are highly unstable and are thus rapidly quenched by hydrogen extracted from the surrounding environment. However, the larger kerogen free radical is stabilized by the extended aromatic system and can be stable through geological time. Although there have been various structure models for different types of kerogen at different level maturity, the main chemical structure of kerogen include the core structures and linkages. Kerogen is defined to be a complex geopolymer and a heterogeneous macromolecule comprised of randomly cross-linked core structures that may be aliphatic, naphthenic, aromatic and/or heteroatomic . The chemical structures of kerogen and the free radicals reactions have been studied widely (Siskin et al., 1995;Sun and P...

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“…7) Larsen, et al reported that the pyrolysis behavior of immature kerogen was significantly altered by removing the inherent radicals. 8,9) Radicals originally present in low-grade coals may recombine upon heating and become cross-linking points for molecules in the coal. In this study, we focused on the possibility that polymerization reaction caused by the recombination of radicals originally existing in coal can deteriorate softening and melting properties, and proposed a mild reduction pretreatment method to remove the radicals, and examined the validity of the proposed method.…”

Section: Improvement Of Coking Property Of Low-grade Coals By Mild Re...mentioning

confidence: 99%

Improvement of Coking Property of Low-Grade Coals by Mild Reduction Treatment

Ashida,

Takahashi,

Ren

et al. 2023

ISIJ Int.

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Kerogen Chemistry 9. Removal of Kerogen Radicals and Their Role in Kerogen Anhydride Decomposition

Cited by 5 publications

References 21 publications

Characteristics of Thermal Bitumen Structure as the Pyrolysis Intermediate of Longkou Oil Shale

Characteristics of Thermal Bitumen Structure as the Pyrolysis Intermediate of Longkou Oil Shale

Temperature and Time Effects on Free Radical Concentration in Organic Matter: Evidence from Laboratory Pyrolysis Experimental and Geological Samples

Improvement of Coking Property of Low-Grade Coals by Mild Reduction Treatment

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