Characterizing the Behavior of Bitumen-Water Systems with the Hydrophilic-Lipophilic Difference Framework

Emulsions of water in bitumen, even in solvent-diluted bitumen, are notorious for their stability. Such stability affects the removal of water in the froth treatment process prior to upgrading of bitumen extracted from mining operations. The literature presents various examples of the use of the hydrophilic-lipophilic difference (HLD) framework to formulate demulsifiers for conventional crude oils, reducing the emulsion stability from hours to minutes when HLD = 0 (phase inversion point). To apply this approach to bitumen emulsions, the HLD of these systems needs to be assessed. A previous attempt to obtain the HLD of bitumen emulsions was incomplete because the suspected surfactant-like and oil-like behavior of polar oils in bitumen, particularly asphaltenes (ASs) and naphthenic acids (NAs), could not be resolved. This question was revisited using a newly established framework for the HLD of polar oils. To this end, microemulsion phase behavior studies were conducted, involving mixtures of ionic and nonionic surfactants with ASs, diluted bitumen, and deasphalted bitumen (maltenes), which led to the realization that ASs do not play a role in HLD when other surfactants are present in the system. Instead, NAs and their dissociation into naphthenates dominate the phase behavior of bitumen emulsions. It was determined that a gradual change in the degree of dissociation of NAs, induced by sodium hydroxide addition, could substantially change the HLD of the system and the accompanying changes in interfacial tension, emulsion stability, and residual water content in the oil phase.

Automated summary

Emulsions of water in bitumen are highly stable, which affects the water removal process in bitumen extraction. Previous studies have used the hydrophilic-lipophilic difference (HLD) framework to reduce emulsion stability, but the HLD of bitumen emulsions remains unclear. This study investigates the role of polar oils, specifically asphaltenes and naphthenic acids, in HLD and finds that naphthenic acids and their dissociation dominate the phase behavior of bitumen emulsions.