Coking propensity of Athabasca bitumen vacuum bottoms in the presence of H-donors — formation and dissolution of mesophase from a hydrotreated petroleum stream (H-donor)

Rahimi, Parviz; Gentzis, Thomas; Kubo, Junichi; Fairbridge, Craig; Khulbe, C P

doi:10.1016/s0378-3820(99)00038-7

Cited by 9 publications

(5 citation statements)

References 23 publications

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“…Meanwhile, the (d w /d t ) max for resins was larger than that of oil sand bitumen and aromatics. These observations might be revealed by the fact that the free radical chain reactions were, to some extent, inhibited by the combination of these free radicals with other free radicals, especially the H free radicals donated from naphthenic rings and aromatic rings. , Nevertheless, it might be suggested that the H free radicals mainly originated from the naphthenic rings, instead of aromatic rings because the condensation reactions of polycyclic aromatics was not remarkable in the T i to T max . Thus, on the basis of the order of resins < oil sand bitumen < aromatics for f N , the negative influence of the combination of alkyl free radicals and H free radicals on cracking reactions for resins was less than that on oil sand bitumen and aromatics, while the interaction between the SARA fraction mentioned above might be responsible for the lowest (d w /d t ) max for asphaltenes compared with aromatics and resins.…”

Section: Resultsmentioning

confidence: 99%

“…62 Therefore, the heat transfer between the surroundings and the interiors of the samples at higher heating rate was not effective so as to require higher temperature to reach the balance of the temperature of samples during the thermal cracking process. 63 The values of dα/dt and temperature corresponding to the specific conversion rate ranging from 0.1 to 0.9 at different heating rates (10,20,50,80,120,200, 500, and 800 K/min) were taken with the Friedman procedure described by the eq 4 to calculate the activation energy E and pre-exponential factors A.…”

Section: Energy and Fuelsmentioning

confidence: 99%

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Thermal Cracking Characteristics and Kinetics of Oil Sand Bitumen and Its SARA Fractions by TG–FTIR

et al. 2017

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The thermal cracking process of oil sand bitumen was investigated via studying the thermal cracking behaviors and online-gas-releasing characteristics of its SARA fractions (saturates, aromatics, resins, asphaltenes) by using TG−FTIR. The results showed that the asphaltenes contributed the most to coke formation of oil sad bitumen according to its largest weighted coke yield compared with that of others. The online FTIR analysis for the gases evolved from the thermal cracking process of oil sand bitumen and its SARA fractions indicated that the gaseous products in the main reaction stage showed more complex composition than those in the volatilization stage, and predominantly consisted of CO 2 , CO, methane, ethylene, other light alkanes and olefins, light aromatics, and hydrogen sulfide. Moreover, the release behaviors of typical gaseous products (CO 2 , CO, methane, ethylene, and light aromatics) for oil sand bitumen and its SARA fractions were different due to the different composition and structure. The thermal-cracking kinetic parameters of oil sand bitumen and its SARA fractions were determined using the iso-conversional Friedman procedure at heating rates of 10 to 800 K/min. The activation energy of oil sand bitumen ranging from 93.74 to 215.99 kJ/mol in the whole thermal cracking process fell in between that of aromatics and resins. The variation of activation energy with the conversion rate for oil sand bitumen during the thermal cracking process was influenced by the interaction between SARA fractions.

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Section: Resultsmentioning

confidence: 99%

Section: Energy and Fuelsmentioning

confidence: 99%

Thermal Cracking Characteristics and Kinetics of Oil Sand Bitumen and Its SARA Fractions by TG–FTIR

et al. 2017

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“…The optical texture development of TCVI (fine-grained mosaics) combined with the wave-like and smooth macroporosity indicates that a higher coking temperature than 490 °C can sharply promote shot-coke formation. A reasonable explanation for the behavior has been reported by Rahimi et al, who stated that free radicals, reacting drastically at a high temperature, would not be stabilized by active hydrogen and, thus, accelerate condensation. In this way, the coking reaction system could only have a quite narrow time window for the lowest viscosity, leading to the hindered growth of the mesophase.…”

Section: Resultsmentioning

confidence: 60%

Correlation of Temperature-Programmed Oxidation with Microscopy for Quantitative Morphological Characterization of Thermal Cokes Produced from Pilot and Commercial Delayed Cokers

et al. 2015

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A wide series of thermal cokes obtained from commercial delayed cokers and a pilot coking plant have been investigated by polarized light microscopy observation, scanning electron microscopy (SEM), and temperature-programmed oxidation (TPO) technology. For discrimination of the characterization of the coke samples, the anisotropy degrees of the cokes are found to be considerably different. According to the series of runs in the pilot plant, the restricted mesophase development in thermal cokes could be ascribed to the increasing severity of coking conditions. A previous proposed signal analysis procedure was then applied to the TPO profiles of the cokes to quantitatively acquire parameters for further correlation. A fairly good linear dependency of optical texture index (OTI) upon the proportion of anisotropic carbon species from TPO (correlation coefficient of 0.984) was observed. All of the results obtained in this and our previous (A temperature-programmed oxidation method for quantitative characterization of the thermal cokes morphologyChenK.XueZ.LiuH.GuoA.WangZ. Chen, K. Xue, Z. Liu, H. Guo, A. Wang, Z. Fuel2013113274279) studies fall within a 95% confidence interval when the dependence of OTI upon the proportion from TPO is considered, therefore clearly demonstrating the validity and adaptability on the convenient determination of the proportion of anisotropic carbon species from TPO for the coke samples ranging from laboratory sources to pilot and even commercial origins. The distribution map of cokes established in this study could be used for quantitatively characterizing the morphology of various thermal cokes.

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“…Hydrogen can also be transferred during thermal conversion by species already present in the petroleum. − Material that have hydrogen transfer properties can also be used as “hydrogen donor” co-feed with the petroleum. ,, The hydrogen that is transferred, is usually present in aliphatic C–H bonds that have bond dissociation energies 20–60 kJ/mol lower than the H–H bond in H 2 . Similarly, the hydrogen is abstracted by free radical species and the hydrogen transfer does not rely on thermally induced bond scission.…”

Section: Discussionmentioning

confidence: 99%

Methyl and Hydrogen Transfer in Free Radical Reactions

Tannous

Klerk

2020

Energy Fuels

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It was speculated that hydrogen transfer was not the only type of transfer reaction that could take place during thermal conversion, and that methyl transfer could also take place. There was a large body of literature on intramolecular methyl migration, but little mention of intermolecular methyl transfer as a potentially important reaction type in free radical systems. Methyl transfer during thermal conversion at 400 °C was investigated using indene, 2-methylindene and α-methylstyrene. It was demonstrated that methyl transfer took place. Reaction products that could be explained only in terms of intermolecular methyl transfer were identified, including products that were formed by transfer of two methyl groups. Thermal conversion that considered both intermolecular methyl transfer and hydrogen transfer highlighted potential implications for industrial practice. Products from methyl transfer were more reactive for thermally induced free radical initiation and hydrogen/methyl transfer reactions. Methyl transfer during molecule-induced homolysis provided a plausible pathway for release of methane that does not require a reaction involving hydrogen and methyl radicals. This work not only showed the importance of intermolecular methyl transfer in free radical systems, but also indicated that methyl transfer as opposed to hydrogen transfer affected the composition and bulk properties of the reaction product.

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Coking propensity of Athabasca bitumen vacuum bottoms in the presence of H-donors — formation and dissolution of mesophase from a hydrotreated petroleum stream (H-donor)

Cited by 9 publications

References 23 publications

Thermal Cracking Characteristics and Kinetics of Oil Sand Bitumen and Its SARA Fractions by TG–FTIR

Thermal Cracking Characteristics and Kinetics of Oil Sand Bitumen and Its SARA Fractions by TG–FTIR

Correlation of Temperature-Programmed Oxidation with Microscopy for Quantitative Morphological Characterization of Thermal Cokes Produced from Pilot and Commercial Delayed Cokers

Methyl and Hydrogen Transfer in Free Radical Reactions

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