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Stephenson, Geoff

doi:10.1049/me:19900184

Cited by 3 publications

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“…The deposition can result in the reduction of reservoir rock permeability and a decrease in the pipe effective diameter. Despite the variety of techniques and methodologies available to evaluate asphaltene deposition inhibition, the addition of dispersants and inhibitors has been the preferred method. − …”

Section: Introductionmentioning

confidence: 99%

Effects of pH and Temperature on the Phase Behavior and Properties of Asphaltene Liquid Films

Kabbach

Santos

2017

Energy Fuels

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Crude oil asphaltenes represent a solubility fraction of petroleum that includes the most polar and most interface-active compounds. Asphaltenes have been involved in solid deposition phenomena in oilfield operations and have produced impractical conditions for oil flow in pipelines and reservoir porous rock. In addition, asphaltenes contribute to the formation of both oil-in-water and water-in-oil emulsions. Therefore, the properties of asphaltene interfacial films are crucial to defining the stabilization or breaking of crude oil emulsions. In this work, the results are presented as a contribution to understanding the elasticity and phase behavior of asphaltene liquid films with changes in subphase pH and temperature. n-Pentane-insoluble asphaltenes (C5I) were extracted from a light crude oil and deposited at the air–water interface from a dichloromethane spreading solution to form two-dimensional monolayers. The C5I films were evaluated using a Langmuir trough under compression at a constant rate. Surface pressure–area and surface potential–area isotherms were interpreted from a mathematic model of the surface pressure. The C5I monolayers displayed an extensive region containing liquid-expanded (LE) and liquid-condensed (LC) phases and a well-identified transition region between these phases. The compressibility of LE films (0.01–0.02 m mN–1) was approximately 5-fold lower than the compressibility of LC films (0.05–0.07 m mN–1). The mixed film compressibility was between the LE and LC film compressibilities. At 10 °C, more compressed films were obtained at pH 4. At 30 °C, more compressed films were found at pH 8. Surface pressure (π) was evaluated as a function of the subphase pH and temperature. At 20 °C, the lowest π was between the pH 4 and 8 isotherms. The highest surface pressure was 52 mN m–1 at 10 °C and pH 8, which denotes higher repulsive forces acting in the film. The elasticity of the asphaltene Langmuir films was affected by the ionization of acidic and basic groups on the asphaltene structure.

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Section: Introductionmentioning

confidence: 99%

Effects of pH and Temperature on the Phase Behavior and Properties of Asphaltene Liquid Films

Kabbach

Santos

2017

Energy Fuels

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“…Regarding the mechanism leading from aggregation to true flocculation, two opposite hypotheses have been summarized by Cimino et al In the lyophobic model, ,, asphaltenes are considered as essentially insoluble in the oil and in common solvents. They remain however dispersed as colloidal particles “peptized” by the “resins” which are less aromatic: adsorbed at the surface of the aggregates, the resins provide steric stabilization against flocculation.…”

Section: Introductionmentioning

confidence: 99%

Reversible Description of Asphaltene Colloidal Association and Precipitation

2002

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Asphaltene in crude oil and in other apolar solvents has intriguing solubility properties which indicate colloidal aggregation. However, none of the various models proposed so far is capable of accounting consistently for all properties. In the present article, we reconsider the current literature and list all robust experimental features redundantly reported on asphaltene solubilization. Then we build a new description, demanding that it should not be contradicted by any one of these listed facts. In our description, asphaltene aggregation and precipitation are distinct steps in a completely reversible process. Aggregation proceeds from specific strong interaction sites located at the periphery of the asphaltene molecules: they drive the reversible association in two-dimensional sheets, a morphology which is consistent with reported scattering and viscosity data. Precipitation eventually occurs, determined by van der Waals attractions between aggregates, when the solubility parameter of the solvent is shifted. One major interest of our description is that it accounts for the remarkable solubilizing properties of the "resins" within a completely reversible scheme.

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“…7) Stephenson confirms that the internal oxides begin to form when carbon content has reduced to 0.005%. 8) Accompanied with the decarburization annealing, the oxidized layer formed on the silicon steel surface. [9][10][11] The selective oxidation kinetics of silicon steel is controlled by the diffusion rate of oxygen atoms.…”

Section: Effect Of Annealing Time On Oxides Phases and Morphology Alomentioning

confidence: 99%

Effect of Annealing Time on Oxides Phases and Morphology along Oxidized Depth of Fe-3%Si Steel during Decarburization

Guo

Dai

Hu³

et al. 2019

ISIJ International

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Cited by 3 publications

References 0 publications

Effects of pH and Temperature on the Phase Behavior and Properties of Asphaltene Liquid Films

Effects of pH and Temperature on the Phase Behavior and Properties of Asphaltene Liquid Films

Reversible Description of Asphaltene Colloidal Association and Precipitation

Effect of Annealing Time on Oxides Phases and Morphology along Oxidized Depth of Fe-3%Si Steel during Decarburization

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