Swelling of Asphaltenes

We report x-ray scattering measurements on asphaltenes and bitumen solutions, with attention to the concentrated regimes. We characterize the data in terms of a correlation length which is indicative of proximity to phase separation in a mixture, rather than the radius-of-gyration more indicative of individual colloids. By studying the behavior of the low-angle asphaltene peak on dilution, we show that asphaltenes swell. These results allow the drawing of a phase diagram with two regimes separated by a critical point: a colloidal regime, and a“ swollen asphaltene” regime, the latter being much larger.