Study of Hydrogen Shuttling Reactions in Anthracene/9,10-Dihydroanthracene−Naphthyl-X Mixtures

Arends, Isabel W. C. E.

doi:10.1021/ef950128f

Cited by 16 publications

(10 citation statements)

References 25 publications

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“…The oxidative coupling of aromatics employs oxygen to induce radical formation that leads to C–C bond formation, but in asphaltenes a high free radical content is already present. This type of C–C bond formation has also been reported using model compounds similar to that used to probe reactions in relation to asphaltenes. , …”

Section: Discussionsupporting

confidence: 60%

Uncatalyzed Hydrogen Transfer during 100–250 °C Conversion of Asphaltenes

2017

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The reactivity and reactions of asphaltenes were explored over the temperature range 100−250°C following reports of reactivity and meaningful free radical content in asphaltenes. This study employed industrial pentane precipitated asphaltenes from Athabasca oilsands bitumen. The presence of free radicals in the asphaltenes feed was confirmed. On heating the asphaltenes to 150°C, the aromatic hydrogen content increased relative to the feed by a factor 1.12. It was also found that on heating the asphaltenes to 150°C the n-heptane insoluble fraction increased from 67% to 75%. Almost no gas phase products were produced. The observed changes were ascribed to hydrogen transfer reactions and addition products formed by combination reactions. Direct evidence of hydrogen transfer reactions taking place in the asphaltenes was obtained through the use of the model systems, α-methylstyrene and cumene, as well as anthracene and 9,10-dihydroanthracene. The extent of hydrogen transfer was of the order 1.8 mg H/g asphaltenes in 1 h at 250°C. Asphaltenes also caused dimerization of model compounds, providing indirect evidence that free radical combination reactions took place in the asphaltenes. Interpretation relying on thermodynamic arguments combined with experimental results indicated that at 250°C the reactive species in asphaltenes were incapable of abstracting hydrogen by hydrogen transfer that had bond strengths (based on homolytic bond dissociation energy) exceeding around 353 kJ mol −1 . Using similar arguments, it was deduced that the ratio of reactive species in asphaltenes capable of abstracting hydrogen with bond strengths in the range around 315−353 kJ mol −1 , compared to transferable hydrogen in asphaltenes with a bond strength less than 315 kJ mol −1 was about 2:1.

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Section: Discussionsupporting

confidence: 60%

Uncatalyzed Hydrogen Transfer during 100–250 °C Conversion of Asphaltenes

2017

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“…This type of increase is suggestive of hydrogen transfer to multinuclear aromatics, as described in Figure 8, which has been reported in the literature. 48,49 Hydrogen transferred in this way would increase the CH 2 content. Note that Figure 8, like the subsequent examples of reactions, were selected for illustrative purposes only, and no claim is made that these specific reactions are taking place.…”

Section: Industrial and Engineering Chemistry Researchmentioning

confidence: 99%

Self-Modeling Multivariate Curve Resolution Model for Online Monitoring of Bitumen Conversion Using Infrared Spectroscopy

Tefera

Agrawal

Jaramillo

et al. 2017

Ind. Eng. Chem. Res.

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For the efficient real-time monitoring of reaction chemistry in a complex mixture using online spectroscopy, it is essential to develop a mathematical tool that can automatically resolve the spectra so that either the spectral or the concentration profile of the changing species can be tracked easily. While self-modeling multivariate curve resolution (SMCR) is a well-suited tool when initial profiles are known beforehand, it is not straightforward to use when dealing with complex mixtures. In this study, a multivariate data analysis algorithm was designed for use with online infrared spectroscopy to provide an instant best estimate of the reaction chemistry of a complex mixture with no additional user input. The investigated process is thermal conversion of oil sands bitumen, and the study employed 43 infrared spectra from samples, collected offline, of products treated at different temperatures and time periods. The resolved spectral and concentration profiles can be used to understand the reaction mechanism of the system. In addition to the concentration and spectral profile, simple parameters were devised to monitor the changes in the key regions of the spectral profiles. In general, the results described the possible reaction mechanism of the investigated system and were consistent with other experimental findings in the literature. Computationally, the algorithm requires only a few seconds to converge and is therefore suitable for online monitoring.

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“…From the equilibrium relation for eqn. (2), K eq (1) = 1.3 exp(Ϫ132 (kJ mol Ϫ1 )), 17 it follows that [AnH ؒ ] = 8 × 10 Ϫ6 M, predicting a complete conversion of 2-methoxyphenol if the induced decomposition were solely determined by the hydrogen abstraction (with k ind = 4 × 10 4 M Ϫ1 s Ϫ1 at 625 K). † † However, in the presence of a high concentration of a hydrogen donor, the hydrogen abstraction is an equilibrium process: hydrogen abstraction from AnH 2 by the phenoxyl radical is in competition with the intramolecular hydrogen abstraction from the methoxyl substituent.…”

Section: Liquid-phase Experimentsmentioning

confidence: 99%

The radical-induced decomposition of 2-methoxyphenol

Dorrestijn¹,

Mulder²

1999

J. Chem. Soc., Perkin Trans. 2

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The thermolysis of 2-methoxyphenol has been studied between 680 and 790 K, applying cumene as a radical scavenger. Two pathways were observed: a homolytic route involving the cleavage of the methoxyl O-C bond, leading to methane and 1,2-dihydroxybenzene, obeying k uni (s Ϫ1 ) = 10 15.2 ± 0.2 exp(Ϫ239 ± 8 (kJ mol Ϫ1 )/RT), and an induced route starting with abstraction of the phenolic hydrogen by cumyl radicals. After intramolecular hydrogen transfer a cascade of reactions yields phenol, 2-hydroxybenzaldehyde, and 2-hydroxybenzyl alcohol. The latter compound decomposes instantaneously into o-quinone methide (o-QM) which is reduced to o-cresol.

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Study of Hydrogen Shuttling Reactions in Anthracene/9,10-Dihydroanthracene−Naphthyl-X Mixtures

Cited by 16 publications

References 25 publications

Uncatalyzed Hydrogen Transfer during 100–250 °C Conversion of Asphaltenes

Uncatalyzed Hydrogen Transfer during 100–250 °C Conversion of Asphaltenes

Self-Modeling Multivariate Curve Resolution Model for Online Monitoring of Bitumen Conversion Using Infrared Spectroscopy

The radical-induced decomposition of 2-methoxyphenol

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