Characterization and Interfacial Behavior of Oil Sands Solids Implicated in Emulsion Stability

Abstract

Model water‐in‐hydrocarbon emulsions were used to assess the configuration of oil sands solids in the interfacial region. The model emulsions consisted of toluene, heptane, and water as well as asphaltenes and solids separated from Athabasca bitumen. A combination of emulsion gravimetric measurements, water drop size measurements, and geometrical considerations was employed to determine the fractional area of the interface occupied by solids and asphaltenes. The probable size and shape of the solid particles adsorbed on the interface was also determined with the assistance of SEM and TEM images and further solids characterizations were made with XRD and particle size distributions. The solids that adsorb at the oil–water interface appear to be clay platelets varying from less than 100 nm up to 500 nm in lateral extent. The fractional interfacial area occupied by the solids increases monotonically with increasing concentration of solids in the bulk solution. At the maximum solids concentration considered, 2.8 and 1.9 kg/m³ asphaltenes, 50% of the interfacial area was occupied by solids. The solids appear to adsorb on the interface as individual particles lying flat on the interface. The average thickness of the solids layer is 8 nm. It is speculated that solids adsorbed at the interface prevent bridging between adjacent water droplets, while particles trapped in the continuous phase increase emulsion stability by preventing close contact amongst water droplets.

Keywords:

• Oil sand solids
• Asphaltenes
• Interfacial configuration
• Adsorption
• Water‐in‐oil emulsions
• Emulsion stability

Acknowledgments

We would like to thank Brenda Mottle for assistance with particle size analysis, Louise Klatzel‐Mudry for assistance with x‐ray diffraction, and Richard Humphrey for the SEM and TEM analysis. The financial support of NSERC, Alberta Ingenuity, AERI, and Imperial Oil, Ltd., is greatly appreciated. We also thank Syncrude Canada, Ltd., for supplying the Athabasca bitumen.