Two-Step Adsorption of Endogenous Asphaltenic Surfactants at the Bitumen–Water Interface
We have performed hanging droplet measurements of a straight-run bitumen (SRB) and its corresponding deasphalted oil (DAO) to investigate the adsorption process at the bitumen–water interface (pH 2.7, T = 90 °C). The analysis of the time and surface pressure dependences of the viscoelastic propertie...
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Published in | Energy & fuels Vol. 26; no. 12; pp. 7236 - 7242 |
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Main Authors | , , , |
Format | Journal Article |
Language | English |
Published |
American Chemical Society
20.12.2012
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Subjects | |
Online Access | Get full text |
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Summary: | We have performed hanging droplet measurements of a straight-run bitumen (SRB) and its corresponding deasphalted oil (DAO) to investigate the adsorption process at the bitumen–water interface (pH 2.7, T = 90 °C). The analysis of the time and surface pressure dependences of the viscoelastic properties show that two types of endogenous surfactants (called A and B) compete for the same interface in the case of SRB. The A species adsorb first, and their molecular characteristics (size and bulk concentration) can be obtained by fitting the data with a diffusion-limited adsorption model. They form fluid-like interfacial layers. The B species, that diffuse more slowly toward the interface, eventually replace the A species to form highly viscous and hardly compressible interfacial layers. The B species belong to the asphaltene solubility class because they are removed by the n-heptane fractionation. They are not present in DAO, which only contains the A species. We surmise that those are also asphaltenes but of higher aliphaticity and/or lower state of aggregation. The possibility that they are resins cannot, however, be eliminated at this stage. |
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Bibliography: | ObjectType-Article-1 SourceType-Scholarly Journals-1 ObjectType-Feature-2 content type line 23 |
ISSN: | 0887-0624 1520-5029 |
DOI: | 10.1021/ef300186e |