Oxidation of Bitumen in the Presence of a Constant Concentration of Oxygen

Herrington, P R

doi:10.1080/10916469808949809

Cited by 38 publications

(32 citation statements)

References 9 publications

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“…19 Our study showed that this correlation is not causal and that the increase in carbonyl content was not the cause of addition reactions. Hence, unless carbonyl groups are responsible for physical changes that cause an increase in viscosity, which was not investigated by this study, an increase in carbonyl content does not cause an increase in viscosity, even though it may be correlated.…”

Section: Discussionmentioning

confidence: 81%

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Hydrocarbon Addition Reactions during Low-Temperature Autoxidation of Oilsands Bitumen

Siddiquee

Klerk

2014

Energy Fuels

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Low-temperature oxidation of bitumen with air in the temperature range of 130−160°C was investigated. Of particular interest were the addition reactions taking place during oxidation, which contributed to the observed increase in viscosity of oxidized bitumen. During the autoxidation of bitumen, the relative aliphatic to aromatic loss-ratio of hydrogen increased from 18:1 to 30:1 when the temperature was increased from 140°C to 150°C and then remained almost the same at 160°C. It coincided with a bitumen oxidation selectivity change reported in the literature. The hydrocarbon class responsible for most addition reactions during bitumen oxidation is the naphthenic-aromatic class. A model compound oxidation study at 130°C found no addition products during paraffin oxidation, low addition product selectivity for naphthenic and alkylaromatic compounds, and no measurable oxidation of aromatics without alkyl groups. It was proposed that the dominant pathway for addition reactions of hydrocarbons is hydrogen disproportionation of free radicals to produce olefins. Free-radical addition to olefins through the formation of C−C bonds explained all of the oxidation selectivity observations from the model compound studies, as well as the addition products identified from their mass spectra. It could also be applied to explain the bitumen oxidation results in these and other studies.

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Section: Discussionmentioning

confidence: 81%

“…19 The method of determination employed by Herrington 19 is briefly described. The concentration of carbonyl and sulfoxide groups in the oxidized bitumen was determined by infrared spectroscopy of a 5% solution of bitumen in chloroform (CHCl 3 ) in a liquid cell with a path length of 1 mm.…”

Section: Extended Autoxidation Of Bitumen At 130°cmentioning

confidence: 99%

Hydrocarbon Addition Reactions during Low-Temperature Autoxidation of Oilsands Bitumen

Siddiquee

Klerk

2014

Energy Fuels

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“…Over the years, a chemical reaction takes place in bitumen increasing the number of heavy aromatic molecules. [1][2][3][4][5] This process is called chemical aging. The aromatic molecules in bitumen, especially the asphaltene molecules, tend to align to form nanoaggregates.…”

Section: Introductionmentioning

confidence: 99%

“…The aging reaction leads also to an increase in the nanoaggregate size 1, 6, 7 correlated with an unwanted increase in bitumen viscosity and brittleness. [1][2][3][4][5] The change in bitumen mechanical properties, which go from "liquid-like" to more "solid-like" during chemical aging finally results in cracks in the pavement and road deterioration. To prevent or reverse the effects of chemical aging, a first step is to gather more knowledge about the nanoaggregate structure and stability in bitumen.…”

Section: Introductionmentioning

confidence: 99%

Cooee bitumen. II. Stability of linear asphaltene nanoaggregates

Lemarchand

Schrøder

Dyre

et al. 2014

The Journal of Chemical Physics

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Asphaltene and smaller aromatic molecules tend to form linear nanoaggregates in bitumen. Over the years bitumen undergoes chemical aging and during this process, the size of the nanoaggregate increases. This increase is associated with an increase in viscosity and brittleness of the bitumen, eventually leading to road deterioration. This paper focuses on understanding the mechanisms behind nanoaggregate size and stability. We used molecular dynamics simulations to quantify the probability of having a nanoaggregate of a given size in the stationary regime. To model this complicated behavior, we chose first to consider the simple case where only asphaltene molecules are counted in a nanoaggregate. We used a master equation approach and a related statistical mechanics model. The linear asphaltene nanoaggregates behave as a rigid linear chain. The most complicated case where all aromatic molecules are counted in a nanoaggregate is then discussed. The linear aggregates where all aromatic molecules are counted seem to behave as a flexible linear chain.

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“…Unfortunately the literature also contains reports that state that oxidation, even at temperatures as low as 60°C and oxidation times as long as 229 h at 130°C, leads to substantial hardening with little lighter liquid products being produced [2,8,11,18]. These studies all dealt with heavy oils, rather than just the asphaltenes fraction.…”

Section: Introductionmentioning

confidence: 99%

Low-temperature oxidative asphaltenes liquefaction for petrochemicals: fact or fiction?

Sánchez

Klerk

2016

Appl Petrochem Res

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Asphaltene is the heavy and heteroatom-rich fraction of petroleum that is rejected during a solvent deasphalting process. In patent literature there are claims that state that this material can be converted into an aromatic petrochemical feedstock by oxidative liquefaction at low temperature. To evaluate the validity of these claims, asphaltenes from an industrial solvent deasphalting process were oxidized with dry and water-saturated air at temperatures in the range 45-100°C. Infrared spectroscopy of the oxidized product confirmed that oxygen was incorporated as C=O and C-O. Under all experimental conditions studied little oxidative degradation was observed that would lead to the production of a petrochemical feedstock. Nevertheless, some observations of scientific value were made about the low-temperature conversion of asphaltenes. During autoxidation with dry air, the n-pentane-insoluble fraction increased. On the contrary, when oxidation was conducted with water-saturated air, the formation of additional n-pentane-insoluble material was suppressed. Mild heating of asphaltenes under nitrogen atmosphere also caused the n-pentane-insoluble content to increase. Spectroscopic evidence showed that esters are formed during oxidation at *100°C. The temperature dependence of this reaction was explained and a possible reaction pathway for cycloalkane to ester conversion was presented. Ester selectivity was determined by the competition between hydrogen abstraction and b-scission of the alkoxy radical.

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Oxidation of Bitumen in the Presence of a Constant Concentration of Oxygen

Cited by 38 publications

References 9 publications

Hydrocarbon Addition Reactions during Low-Temperature Autoxidation of Oilsands Bitumen

Hydrocarbon Addition Reactions during Low-Temperature Autoxidation of Oilsands Bitumen

Cooee bitumen. II. Stability of linear asphaltene nanoaggregates

Low-temperature oxidative asphaltenes liquefaction for petrochemicals: fact or fiction?

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