Chapter 2
2.4. Emulsion of water in diluted bitumen
Chapter 1 briefly discussed the formation of water in diluted bitumen
emulsions during bitumen froth treatment. Crude oils are complex mixtures of a
number of species that differ significantly in molecular weight, structure and
elementary composition. Therefore water in diluted bitumen exhibits different
characteristics from other water-in-oil emulsions, especially its stability due to the
surface-active components and fine clay solids.
Most often used way to classify species in crude oil is in solubility classes.
Asphaltenes are defined as the components of crude oil that are insoluble in
paraffinic hydrocarbons such as n-pentane or n-heptane, but that are soluble in
aromatic solvents like toluene. The elemental analysis of asphaltenes shows that
carbon (~ 80 wt.%) and hydrogen (~ 8 wt.%) are the main components of their
structure, and that heteroatoms (S, O, N, Ni, V) are commonly present in amounts
that vary considerably for asphaltenes from different sources [23].
Several tentative chemical structures have been proposed for asphaltenes.
Figure 2.5 shows the proposed structure of asphaltenes present in Athabasca
bitumen [24]. It contains small groups of aromatic rings interconnected by alkyl
chains and naphthenic and aliphatic rings, in a fashion that has been termed the
archipelago model[24].
22