MASc alumnus University of Toronto Toronto, Ontario, Canada
Abstract: Naphthenic acids (NAs) are one of the most important factors in the formation and stabilization of bitumen emulsions. While NAs are hydrophobic and oil-soluble, their neutralized form, sodium naphthenates (NaNs), can be highly hydrophilic. Although the appropriate NA/NaN ratio should lead to phase inversion and very low interfacial tensions (IFTs < 0.1 mN/m), the partition of a hydrophobic NaN fraction prevents achieving very low IFTs. This work uses the hydrophilic-lipophilic difference (HLD) combined with the net-average curvature (NAC) model to guide formulation efforts involving the addition of a mixture of surfactants (sodium dihexyl sulfosuccinate -SDHS- and sodium dioctyl sulfosuccinate -SDOS or AOT) to aid in the phase inversion process and in achieving very low IFTs. To this end, the HLD-NAC model was combined with a neutralization (to account for the concentrations of NaN and NA) + polar oil segregation model (to account for the segregation of NA to the interface). The combination of surfactants can achieve ultralow IFTs at the conditions of bitumen production in model oils. The HLD-NAC + segregation model was further used to predict the conditions of emulsion inversion (where the lower emulsion stability is expected) with diluted bitumen. The HLD-NAC predicted neutralization fraction (NaN/initial NA) where the phase inversion occurs is consistent with the neutralization fraction at which the lowest bitumen emulsion stability was obtained.