Further studies of coal oxidation

Rhoads, Carol A.; Senftle, J.T.; Coleman, Michael M.; Davis, A. W.; Painter, Paul C.

doi:10.1016/0016-2361(83)90104-7

“…Activation energies for the oxidation of some asphaltic materials [31] for 13 CH 3 groups bound to acidic sites. Consequently, the production of phenols and aromatic carboxylic acids upon air oxidation is apparent, and complies with a mechanism where oxygen reacts with diaryl ether and dimethylene bridges, as in coal [23,24,29,34]. Reactions of type III can create tertiary and benzylic alcohols.…”

Section: Carbon-13 and Fluorine-19 Nmr Spectroscopymentioning

confidence: 70%

“…Once the fOCH 2 f sites are exhausted by reaction with oxygen, then reaction II takes precedence. Other oxidizable groups include sulfides, sulfoxides, aldehydes, and diaryl methylenes (fCH 2 f) which can form sulfoxides, sulfones, carboxylic acids, and ketones, respectively [28,29]. These oxidation reactions generally shift downfield the 13 C magnetic resonance positions of a-carbon atoms proximal to polar groups (e.g.…”

Section: Carbon-13 and Fluorine-19 Nmr Spectroscopymentioning

confidence: 99%

The low temperature oxidation of Athabasca oil sand asphaltene observed from 13C, 19F, and pulsed field gradient spin-echo proton n.m.r. spectra

Desando

¹

,

Lahajnar

²

,

Ripmeester

³

et al. 1999

Fuel

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The low temperature oxidation of Athabasca oil sand asphaltene observed from 13C, 19F and pulsed field gradient spin-echo proton n.m.r. spectra Desando, Michael A.; Lahajnar, Gojmir; Ripmeester, John A.; Zupancic, Ivan AbstractCarbon-13 and fluorine-19 nuclear magnetic resonance spectra of chemically derivatized, by phase transfer methylation and trifluoroacetylation, Athabasca oil sand asphaltene, reveal a broad site distribution of different types of hydroxyl-containing functional groups, viz., carboxylic acids, phenols, and alcohols. The low temperature air oxidation of asphaltene, at ca. 130ЊC for 3 days, generates a few additional carboxyl and phenolic groups. These results are consistent with a mechanism in which diaryl methylene and ether moieties react with oxygen. Self-diffusion coefficients, from the pulsed field gradient spin-echo proton magnetic resonance technique, suggest that low temperature oxidation does not appreciably alter the average particle size and diffusion properties of asphaltene in deuterochloroform. ᭧

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“…Activation energies for the oxidation of some asphaltic materials [31] are in the range 64-109 kJ mol for 13 CH 3 groups bound to acidic sites. Consequently, the production of phenols and aromatic carboxylic acids upon air oxidation is apparent, and complies with a mechanism where oxygen reacts with diaryl ether and dimethylene bridges, as in coal [23,24,29,34]. Reactions of type III can create tertiary and benzylic alcohols.…”

mentioning

confidence: 70%

“…80 h the phenol content decreases owing to condensation of hydroxyls to form ethers and esters [29]. Infrared analysis reveals that methyl ester and ether groups in PTM reacted coals [39] are stable up to 254ЊC.…”

mentioning

confidence: 99%

99/02454 The low temperature oxidation of Athabasca oil sand asphaltene observed from 13C, 19F, and pulsed field gradient spin-echo proton n.m.r. spectra

1999

Fuel and Energy Abstracts

0

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The low temperature oxidation of Athabasca oil sand asphaltene observed from 13C, 19F and pulsed field gradient spin-echo proton n.m.r. spectra Desando, Michael A.; Lahajnar, Gojmir; Ripmeester, John A.; Zupancic, Ivan AbstractCarbon-13 and fluorine-19 nuclear magnetic resonance spectra of chemically derivatized, by phase transfer methylation and trifluoroacetylation, Athabasca oil sand asphaltene, reveal a broad site distribution of different types of hydroxyl-containing functional groups, viz., carboxylic acids, phenols, and alcohols. The low temperature air oxidation of asphaltene, at ca. 130ЊC for 3 days, generates a few additional carboxyl and phenolic groups. These results are consistent with a mechanism in which diaryl methylene and ether moieties react with oxygen. Self-diffusion coefficients, from the pulsed field gradient spin-echo proton magnetic resonance technique, suggest that low temperature oxidation does not appreciably alter the average particle size and diffusion properties of asphaltene in deuterochloroform. ᭧

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“…Kok, 2008;Ledesma, Kalish, Nelson, Wornat, & Mackie, 2000;Liotta, Brons, & Isaacs, 1983;MacPhee, Giroux, Charland, Gransden, & Price, 2004;Mahidin, Usui, Ishikawa, & Hamdani, 2002;Ogloza & Malhotra, 1989;Painter, Snyder, Pearson, & Kwong, 1980;Rhoads, Senftle, Coleman, Davis, & Painter, 1983;Wu, Robbins, Winschel, & Burke, 1988). The changes of IR/FTIR spectra observed for a coal i.e.…”

Section: Ir/ftir Spectroscopymentioning

confidence: 99%