Suppression of Homogeneous Asphaltene Precipitation by Mineral-Induced Nucleation

The
impact of mineral particles on the phase transition mechanism
of asphaltenes has received comparatively little attention, despite
their presence in significant quantities in oil sands and relatively
lower amounts in conventional crudes. In this study we investigate
the phase transition mechanism of asphaltenes in oil-titrant system
as a function of the mineral concentration using a titration flow
cell and ultra-small-angle X-ray scattering (USAXS). The results demonstrate
that heterogeneous asphaltene nucleation dominates as the asphaltene
precipitation mechanism at elevated mineral particle concentrations
in toluene-diluted bitumen with asphaltene precipitation induced by n-heptane titration. Additionally, significant mineral–mineral
aggregation is observed before a bulk asphaltene phase transition.
When mineral particles are present at the composition tested, the
homogeneous nucleation mechanism for asphaltenes is significantly
suppressed. We anticipate these findings will be important for the
design of oil sands extraction processes to remove minerals and water
prior to refining and in the modeling of well-bore asphaltene deposition
in conventional crude oils.