Asphaltenes and Other Natural Surfactants from Cerro Negro Crude Oil. Stepwise Adsorption at the Water/Toluene Interface: Film Formation and Hydrophobic Effects
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- 作者：Só ; crates Acevedo ; Belsay Borges ; Felipe Quintero ; Vincent Piscitelly ; and Luis B. Gutierrez
- 刊名：Energy & Fuels
- 出版年：2005
- 出版时间：September 2005
- 年：2005
- 卷：19
- 期：5
- 页码：1948 - 1953
- 全文大小：97K
- 年卷期：v.19,no.5(September 2005)
- ISSN：1520-5029
文摘
The adsorption of asphaltenes and other natural surfactants at the water/toluene interfacehas been studied here, using both the ring and pendant drop method to measure the interfacialtension (
). The dependence of on the logarithm of the sample concentration (ln C) (representedas the (ln C) isotherm) leads to a stepwise isotherm similar to that corresponding to theadsorption of asphaltenes at the toluene/silica interface. As is the case for the toluene/silicainterface, the stepwise (ln C) isotherm seems to be the result of adsorption at the toluene/waterinterface of molecules, as well as aggregates formed in solution. Once adsorbed, these aggregatesflocculate at the interface, leading to the well-known three-dimensional asphaltene films. Inagreement with previous evidence from thermal lens experiments, the onset of asphalteneaggregation was observed near a sample concentration of C = 60 mg/L. Although the presence ofaliphatic (acid fraction soluble in heptane, AFSH) and other types of acidic components in theasphaltene mixture increases the interfacial activity of asphaltenes, the removal of thesecomponents does not prevent the adsorption and leads to a film with an interfacial tension of = 26 mJ/m2. This shows that such asphaltene films are less hydrophobic than what might beexpected. As suggested by the detailed description of the results given in this paper, the asphalteneinterfacial film is a mixed film formed by both AFSH and asphaltenes, where the role of AFSHis to reduce the value of and the role of asphaltenes is to reduce hydrophobic effects by forminga film that effectively separates oil from water.
). The dependence of on the logarithm of the sample concentration (ln C) (representedas the (ln C) isotherm) leads to a stepwise isotherm similar to that corresponding to theadsorption of asphaltenes at the toluene/silica interface. As is the case for the toluene/silicainterface, the stepwise (ln C) isotherm seems to be the result of adsorption at the toluene/waterinterface of molecules, as well as aggregates formed in solution. Once adsorbed, these aggregatesflocculate at the interface, leading to the well-known three-dimensional asphaltene films. Inagreement with previous evidence from thermal lens experiments, the onset of asphalteneaggregation was observed near a sample concentration of C = 60 mg/L. Although the presence ofaliphatic (acid fraction soluble in heptane, AFSH) and other types of acidic components in theasphaltene mixture increases the interfacial activity of asphaltenes, the removal of thesecomponents does not prevent the adsorption and leads to a film with an interfacial tension of = 26 mJ/m2. This shows that such asphaltene films are less hydrophobic than what might beexpected. As suggested by the detailed description of the results given in this paper, the asphalteneinterfacial film is a mixed film formed by both AFSH and asphaltenes, where the role of AFSHis to reduce the value of and the role of asphaltenes is to reduce hydrophobic effects by forminga film that effectively separates oil from water.