Aliphatic structural elements of a Pocahontas No. 3 coal

Stock, Leon M.; Wang, Shih Hsien

doi:10.1021/ef00016a018

Cited by 20 publications

(9 citation statements)

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“…3 coal [3]. This oxidation reaction produced more benzenetri-, tetra-, and pentacarboxylic acids than benzenedicarboxylic acids, indicating that compounds with three or more rings predominated.…”

Section: Resultsmentioning

confidence: 93%

Chemical constitution of Pocahontas No. 3 coal

Stock¹,

Obeng²

1993

Energy Fuels

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A new method for the definition of the larger aromatic structural elements in high-rank coals has been developed. The procedure involves the oxidative decomposition of the coal with oxygen in basic solution and the subsequent decarboxylation of the aromatic carboxylic acids to yield a mixture of aromatic compounds that can readily be analyzed by conventional methods. This approach has been tested with pure compounds and applied to Pocahontas No. 3 coal.

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Section: Resultsmentioning

confidence: 93%

Chemical constitution of Pocahontas No. 3 coal

Stock¹,

Obeng²

1993

Energy Fuels

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“…To determine the relationship between the number of oxidized aromatic carbon atoms and that of eliminated clusters, all of the aromatic carbon atoms involved in oxidized clusters should be oxidized. In general, liquid-phase oxidation of fused aromatic rings forms polycarboxylic benzenes − while the oxidation can eliminate monoaromatic rings as shown in Figure . This suggests a difficulty of elimination of clusters of fused aromatic rings under the present conditions even if they are oxidized.…”

Section: Resultsmentioning

confidence: 99%

Evaluation of Macromolecular Structure of a Brown Coal by Means of Oxidative Degradation in Aqueous Phase

et al. 1999

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Acid-washed Morwell brown coal was oxidized at 85 °C in a 0.5 N Na2CO3 aqueous solution in a closed system, through which oxygen gas was bubbled. The oxidation took 1−12 h and consumed 1.8−5.8 mmol of O2 per gram of the coal. Analyses of the products revealed that aromatic carbon was selectively oxidized into carboxyls in the residual solid (oxidized coal), water-soluble nonaromatic acids, and carbon dioxide, while aliphatic carbon was minimally involved in the reaction. Considering that the coal consists of two major structural elements, aromatic clusters (mono- or fused aromatic rings with peripheral groups) and intercluster bridges (alkyl groups and ethers connecting clusters), it was concluded that the oxidation converted aromatic carbons bonded to bridges into peripheral carboxyl groups on the neighboring clusters and also converted the other aromatic carbons into nonaromatic acids or carbon dioxide. According to the mechanism of the oxidation, which decomposed the macromolecular network of the coal-eliminating clusters and converting bridges into peripherals, the number of carboxyls formed as peripherals was expected to equal that of bridges which were bonded to eliminated clusters. From the relationship between the decrease in the amount of aromatic carbon and the corresponding increase in the amount of carboxylic carbon, the average number of bridges per eliminated cluster was estimated as 2.9 and 1.3 in the early and later stages of the oxidation, respectively, assuming the average number of aromatic carbon atoms per cluster to be 6. The mass fraction of solvent-extractable material increased as oxidation progressed and reached 0.97 after 12 h of oxidation. The oxidation thus enabled us to determine the quantitative relationship between the decrease in the number of bridges and clusters and the increase in the proportion of low-molecular-mass network fragments.

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“…The possible source of diacids has been thought to correspond to polymethylene bridges connecting aromatic units, ,,− and hydroaromatic entities . Stock and Wang have considered that 1-aryl-substituted indane could be a potential precursor of 2 …”

Section: Resultsmentioning

confidence: 99%

“…The ruthenium ion catalyzed oxidation (RICO) method has been commonly used for recognition of aliphatic bridge structures and substituent of coal, − asphaltenes , and kerogens. , This method gives us information on not only aliphatic bridges and functionality but also aromatic entities 3-8 within the coal structure. Referring to hydroaromatic entities, Stock and co-workers ascribed formation of some aliphatic diacids to the oxidation of indane and tetralin type structures. , Although this valuable information is given to us by the RICO method, mass balance of oxidation products from coals, which is in general calculated from recognizable acid products by chromatographic methods and CO 2 formation, is rather low. This limitation prompted us to perform investigations in detail for improving mass balance and efficiency of this method to gain more insight.…”

Section: Introductionmentioning

confidence: 99%

Reexamination of the RICO Method

et al. 1998

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Information about bridge structure and functionalities has been considered to be crucial in estimating the reactivity of coals, and the purpose of this study is to improve the validity of the RICO technique in the determination of aliphatic bridges and functional groups using a Japanese Taiheiyo coal. It was found that room temperature, which had been commonly employed previously, is insufficient for efficient oxidation kinetics and higher temperature such as 40 °C increased the oxidation kinetics 2-fold. Candidates for the remarkable amounts of resolved aliphatic polycarboxylic acid products are thought to be the corresponding polyaryl-substituted aliphatic cross-linkages and various hydroaromatic species. Remarkable amounts of polymeric aliphatic fraction were also formed after RICO. Much higher amounts of benzenepolycarboxylic acids were recovered, and significant improvement of carbon mass balance was achieved contrary to previous reports.

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Aliphatic structural elements of a Pocahontas No. 3 coal

Cited by 20 publications

References 0 publications

Chemical constitution of Pocahontas No. 3 coal

Chemical constitution of Pocahontas No. 3 coal

Evaluation of Macromolecular Structure of a Brown Coal by Means of Oxidative Degradation in Aqueous Phase

Reexamination of the RICO Method

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