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Abstract
The flocculation of aqueous bitumen emulsion during transportation and processing depends mostly on the electrical properties of bitumen-water interface. The aim of this study is to show how such interface is affected by the resins/asphaltenes ratio (r/a) of the bitumen. Our results indicate that the r/a controls the interfacial composition and the stability of the bitumen droplets in a water-continuous medium. Moreover, it is shown that the r/a is primarily responsible for maintaining diffusion of polar components inside the bitumen droplet. Such non-equilibrium behavior of various bitumen polar components takes place during the dispersion manufacturing and/or maturation phase. In this work, the asphaltenes and resins contents of a bitumen series were determined. In addition, the acid-base properties of the same bitumen series were studied by non-aqueous potentiometric titration method. The nature and the amount of acidic and basic functionaliti present in the bitumen were evaluated by comparison with the acid-base model compounds such as carboxylic acid, benzoic acid and pyridine. Furthermore, the interfacial properties of the acidic aqueous bitumen dispersions were studied by contact-angle and zeta potential measurements. The overall results indicate that stable bitumens dispersions are obtained with bitumens having high values of the resins/asphaltenes ratios.
ACKNOWLEDGMENTS
This study was supported by the Shell Recherche S.A. Dr. M.F. Morizur and D. Rabiot are gratefully acknowledged for stimulating discussions.