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.