Influence of High Asphaltene Feedstocks on Processing

Abu-Khader, Mazen M.; Speight, James G.

doi:10.2516/ogst:2007049

Cited by 16 publications

(7 citation statements)

References 32 publications

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“…Asphaltenes comprise substantial fractions from the residue of bitumen and heavy oil distillation. , They are the most massive (high molecular weight), most complex, and most polar components of heavy oils and bitumen. , Asphaltenes are insoluble in light alkanes like n -pentane, n -hexane, or n -heptane and soluble in aromatic solvents like benzene and toluene. , Different average structures and molecular weights have been proposed for asphaltenes based on their elemental analysis and their behaviors on petroleum processing. , Two molecular architectures are widely accepted nowadays as asphaltenes structures, i.e., the island structure and the archipelago structure. In the island structure, one polycyclic aromatic hydrocarbon (PAH) containing an average of seven fused aromatic rings is connected to peripheral alkyl chains .…”

Section: Introductionmentioning

confidence: 99%

“…1,5 Different average structures and molecular weights have been proposed for asphaltenes based on their elemental analysis and their behaviors on petroleum processing. 6,7 Two molecular architectures are widely accepted nowadays as asphaltenes structures, i.e., the island structure and the archipelago structure. In the island structure, one polycyclic aromatic hydrocarbon (PAH) containing an average of seven fused aromatic rings is connected to peripheral alkyl chains.…”

Section: Introductionmentioning

confidence: 99%

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New Pathways for Asphaltenes Upgrading Using the Oxy-Cracking Process

et al. 2016

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Solvent deasphalting of the bottom of vacuum distillation columns (vacuum residue, VR) is a process practiced worldwide. In Northern Alberta, a solvent deasphalting plant was designed to process up to 4000 tons/day of the asphaltenic pitch. Asphaltenes oxy-cracking in liquid phase could be a new approach to asphaltenes upgrading and conversion into valuable chemicals. Oxy-cracking is a combination of oxidation and cracking in basic aqueous media at moderate temperatures (170–225 °C) and pressures (300–500 psi). This process could act very selectively producing smaller amounts of greenhouse gases like CO2, thus being considered environmentally friendly. In this work, a mild oxy-cracking treatment of C5-asphaltenes solid from Athabasca vacuum residue was investigated. The reaction kinetics and possible reaction mechanism for C5-asphaltenes oxy-cracking in water under alkali conditions were studied. Products solubilized under different severities were characterized using Fourier transform infrared and nuclear magnetic resonance spectroscopies, simulated distillation, elemental analysis, and ultraviolet–visible spectrophotometry to investigate the structure of solubilized products and changes in asphaltenes structures after the reaction. A model based on sequential-parallel reactions from the asphaltenes to water-soluble products and CO2 was found to describe the process successfully. Products of oxidized functionalities like carboxylic acids, their salts, methyl ethers and esters, and sulfur-oxidized forms plus phenolics were determined as the most significant fractions soluble in water. Solubilization of asphaltenes in water could also decrease challenges regarding facilities and pipelines plugging.

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Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

New Pathways for Asphaltenes Upgrading Using the Oxy-Cracking Process

et al. 2016

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“…Asphaltenes are a hugely significant financial quandary for oil upgrading . Out of solution, they can form solid deposits in wells and pipelines, thus affecting both oil recovery and transportation.…”

Section: Introductionmentioning

confidence: 99%

Importance of the Inclusion of Dispersion in the Modeling of Asphaltene Dimers

Mackie¹,

DiLabio²

2010

Energy Fuels

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Modeling of asphaltenes presents many challenges, not least of which is their large size and the lack of definitive experimental structure information. However, a further fundamental issue of importance is the ability of the modeling methodology to accurately predict noncovalent interactions, particularly dispersion (London) forces. The self-aggregation properties of asphaltenes are primarily driven by such interactions. Therefore, for a modeling approach to be insightful, dispersion must be accounted for. This point is illustrated in this work by examining the effect of dispersion on the conformer distribution for a series of asphaltene model dimers, including perylene bisimide-type molecules and for a model of Maya asphaltene. Inclusion of dispersion using dispersion-correcting potentials on standard density-functionals is shown to be critical to both structure and conformer population for these noncovalently bound dimers. For the Maya asphaltene, a previously postulated “open” structure is shown to be ca. 9 kcal/mol less stable than a conformer that allows for greater π−π overlap within its central archipelago-type moiety. This finding is in line with recent NMR work, which indicates that “closed” structures dominate for asphaltenes. N,N′-dimethyl-perylene bisimide dimer has a binding energy (BE) of up to 29 kcal/mol, while the more complex N,N′-(1-hexylheptyl)-perylene bisimide model is slightly less strongly bound (BE = 25 kcal/mol) since the large alkyl substituents restrict the ability of the extensive π-regions to overlap. Such conclusions cannot be drawn when methods that do not incorporate dispersion, e.g., the B3LYP density-functional, are used.

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“…The structure of asphaltenes is formed by polycyclic aromatic cores bonded to aliphatic chains containing heteroatoms such as nitrogen, oxygen, sulfur, and metals such as vanadium, iron, and nickel. , Inside the asphaltene molecular structure, the heteroatom position and content change the overall molecular polarity and so its aggregation behavior . Asphaltenes contain polar and non-polar groups (i.e., amphiphilic behavior) that facilitate the self-association, nucleation, and growth. ,,, This behavior leads to several problems during oil production and processing such as formation damage, − transportation, − and refining. − However, there is no consensus in the literature about the size, shape, and structure of the asphaltene molecules and the nanoaggregates nature the molecular mechanisms that generate their formation . Hence, the understanding of the self-association behavior of asphaltenes has been the leading research goal through years by applying molecular simulation and experimental tests. − However, asphaltenes represent a whole family in the crude oil, and the difficulty to experimentally isolate a single asphaltene molecule causes a lack in the understanding of the asphaltenes’ interactions with themselves and with other molecules. , A variety of structures have been proposed based on asphaltene properties obtained experimentally .…”

Section: Introductionmentioning

confidence: 99%

Molecular Dynamics Study of the Aggregation Behavior of Polycyclic Aromatic Hydrocarbon Molecules in n-Heptane–Toluene Mixtures: Assessing the Heteroatom Content Effect

et al. 2021

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This study is focused on evaluating the aggregation behavior of four asphaltene molecules (PA3-type) dissolved in three different solvents. Hence, solution models composed of asphaltenes dissolved in toluene, n-heptane, and mixtures of n-heptane and toluene (known as heptol), were evaluated with molecular dynamics (MD) simulations. For MD calculations, four PA3-type structures were chosen to evaluate the effect of the location of one heteroatom in the polyaromatic core on the aggregation behavior. The first structure consists of only a CH structure, the second has sulfur, the third has nitrogen, and the last one contains oxygen. The heteroatom was replaced in the same location in one of the five-membered rings in the center of the molecule to test the different chemical effects induced by these heteroatoms. Molecules with the heteroatoms showed a higher aggregation tendency in n-heptane than in heptol-50 and toluene, with an average size of 12.8, 6.2, and 2.4 molecules per aggregate, respectively, whereas the PA3 molecule with no heteroatom forms less and smaller aggregates. The inclusion of only one heteroatom increases the polarity and the planarity of the molecule, increasing the attractive interaction energies (140−160% in n-heptane) and the overall aggregation tendency. The molecule with the sulfur heteroatom forms bigger and more stable aggregates than molecules with oxygen and nitrogen. In conclusion, the inclusion of heteroatoms in the PA3 structure increases the polarity and planarity of the molecule, improving the aggregation tendency in all solvents, notoriously in n-heptane.

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Influence of High Asphaltene Feedstocks on Processing

Cited by 16 publications

References 32 publications

New Pathways for Asphaltenes Upgrading Using the Oxy-Cracking Process

New Pathways for Asphaltenes Upgrading Using the Oxy-Cracking Process

Importance of the Inclusion of Dispersion in the Modeling of Asphaltene Dimers

Molecular Dynamics Study of the Aggregation Behavior of Polycyclic Aromatic Hydrocarbon Molecules in n-Heptane–Toluene Mixtures: Assessing the Heteroatom Content Effect

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