Surface Thermodynamics for Polar Adsorbates on Wyodak Coals

Glass, Amy S.; Wenger, Eston K.

doi:10.1021/ef970117h

Cited by 4 publications

(3 citation statements)

References 21 publications

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“…Using this approach, the surface tensions obtained for the seven molecules shown in Figure vary from 64 to 110 mJ/m 2 . In comparison, experimental surface tensions for carbon, graphite, and asphaltenes are 95.67, 100−120, and 41 mJ/m 2 , respectively.…”

Section: Aggregation Modelmentioning

confidence: 95%

Thermodynamic Modeling of Asphaltene Aggregation

Rogel¹

2004

Langmuir

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A new molecular thermodynamic model for the description of the aggregation behavior of asphaltenes in different solvents is presented. This new model is relatively simple and strictly predictive and does not use any experimental information from asphaltene solutions. In this model, asphaltene aggregates are described as composed of an aromatic core formed by stacked aromatic sheets surrounded by aliphatic chains. The proposed model qualitatively predicts the asphaltene aggregation behavior in a series of different solvents. In particular, the experimental trends observed for the variation of aggregate size with (1) asphaltene molecular characteristics (condensation index, aromaticity, and chain length), (2) asphaltene concentration, (3) solvent characteristics, and (4) temperature have been successfully reproduced by the proposed model. The model also provides a plausible explanation for the existence or absence of a critical micelle concentration (cmc) for asphaltene solutions. Specifically, the model predicted that the asphaltenes with low aromaticities and low aromatic condensations do not exhibit cmc behavior. Finally, the obtained results clearly support the classical model for asphaltene aggregates.

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Section: Aggregation Modelmentioning

confidence: 95%

Thermodynamic Modeling of Asphaltene Aggregation

Rogel¹

2004

Langmuir

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“…A considerable amount of work has been done on the solvent swelling of coals, which has given rise to similar hypotheses of solvent-induced conformational flexibility in these macromolecular networks (Brenner 1984;Larsen and Mohammadi 1990;Glass and Stevenson 1996;Glass and Wenger 1998). The fewer reports on the solvent swelling behaviour of peats and soil organic matter have generally yielded similar support to the hypothesis of conformational flexibility (Chen and Schnitzer 1989;Lyon and Rhodes 1993;Lyon 1995).…”

Section: Evidence In Support Of Structural Flexibility In Complex Orgmentioning

confidence: 96%

Flexible conformation in organic matter coatings: An hypothesis about soil water repellency

Roy¹,

McGill²

2000

Can. J. Soil. Sci.

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Flexible conformation in organic matter coatings: An hypothesis about soil water repellency. Can. J. Soil Sci. 80: 143-152. Some soils develop severe water repellency several years or decades following oil contamination. We previously reported that soil water repellency is completely eliminated by extraction with amphiphilic solvents, but barely reduced by extraction with nonpolar solvents. We report here on solvent-induced reversible soil water repellency. Our results indicate that: (i) water repellency is completely eliminated following extraction with amphiphilic solvent, but partially restored following subsequent exposure to nonpolar, non-H-bonding solvent; (ii) extraction with nonpolar, non-H-bonding solvent generates water repellency in readily wettable control wettable soils, but not in pristine wettable soils, and (iii) repeated sequential extractions alternating between amphiphilic and nonpolar, non-H-bonding solvent increase extractable material and reduce the magnitude of solvent-induced soil water repellency with time.We attribute reversible soil water repellency to solvent-induced changes in the conformation of causative agents of soil water repellency. Recent literature reports on the structural flexibility of "insoluble" organic macromolecules are discussed for supporting evidence. We propose that exposure to nonpolar, non-H-bonding solvents induces stretching of surface-exposed, nonpolar moieties (i.e. alkyl chains), whereas exposure to polar, H-bonding solvents induces their coiling. These solvent-induced conformational changes are retained upon solvent removal. Our results indicate that the wettability of oil-contaminated soils depends on both the interfacial conformation and the fractional coverage of their surface-exposed nonpolar moieties. Certains sols acquièrent une grave imperméabilisation à l'eau plusieurs années, voire des décennies, après une contamination par le pétrole. Dans une précédente communication, nous signalions que l'imperméabilité à l'eau est complètement éliminée par extraction au moyen de solvants amphiphiles, mais qu'elle est à peine diminuée en présence de solvants non polaires. Nous traitons ici de l'imperméabilité réversible induite par des solvants. Il ressort de nos observations que i) ce type d'imperméabilité est éliminé complètement après extraction au moyen de solvants amphiphiles, mais qu'il est rétabli partiellement après exposition subséquente à un solvant non polaire sans liaison hydrogène, ii) l'extraction par un solvant de ce type provoque l'imperméabilité dans les sols contaminés témoins à mouillage facile, mais pas dans les sols mouillables non contaminés et iii) ces extractions séquentielles répétées, utilisant en alternance un solvant amphilile et un solvant sans liaison hydrogène non polaire produisent davantage de matériel extractible et réduisent à terme l'importance de l'hydrophobicité du sol due au solvant. Cette réversibilité de l'hydrophobicité du sol est attribuée au changement solvanto-induit de conformation des agents causaux de l'hydrophobic...

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“…Using this approach, the surface tensions obtained for the seven molecules shown in Figure vary from 64 to 110 mJ/m 2 . As a comparison, experimental values for carbon (95.67 mJ/m 2 ), graphite (100−120 mJ/m 2 ), and asphaltenes (41 mJ/m 2 ) are given.…”

Section: Micellization Modelmentioning

confidence: 99%

Asphaltene Aggregation: A Molecular Thermodynamic Approach

Rogel

2002

Langmuir

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The aggregation behavior of asphaltenes in apolar solvents is studied using a molecular thermodynamic approach. The theory is based on a molecular model for asphaltene aggregates that describes them as aromatic cores, composed of stacked aromatic sheets, surrounded by aliphatic chains. Using this simple molecular model, an analytical expression is developed for the free energy of aggregation that incorporates five contributions due to (1) transfer of the polyaromatic rings from the solvent into the aromatic core, (2) mixing of the aliphatic chains with the solvent, (3) deformation of the aliphatic chains, (4) steric repulsion among the aliphatic chains, and (5) aggregate core−solvent interactions. The proposed approach provides a qualitative description of the main experimental trends observed for asphaltene aggregation. Specifically, the experimentally observed variation of cmc values and aggregate size with (1) asphaltene molecular characteristics, (2) asphaltene concentration, (3) solvent composition, and (4) temperature has been qualitatively reproduced by the theory. In addition, the thermodynamic molecular model developed does not utilize any information derived from experiments on asphaltene solutions, and therefore, it is strictly predictive.

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Surface Thermodynamics for Polar Adsorbates on Wyodak Coals

Cited by 4 publications

References 21 publications

Thermodynamic Modeling of Asphaltene Aggregation

Thermodynamic Modeling of Asphaltene Aggregation

Flexible conformation in organic matter coatings: An hypothesis about soil water repellency

Asphaltene Aggregation: A Molecular Thermodynamic Approach

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