Aggregation of asphaltenes in organic solvents using surface tension measurements

The critical micelle concentrations (CMC) of four asphaltenes in different solvents were obtained by surface tension measurements. The CMC values ranged from 1 to 30 g/l and depended on the asphaltene and the solvent used. These values were empirically correlated to the Flory–Huggins interaction parameter. Molecular areas of the asphaltene molecules at the solvent–air interfaces were also calculated. The wide range in determined molecular areas (1.0–4.0 nm2) can be attributed to significant differences in asphaltene–solvent interactions. As a consequence of these differences, the orientation of molecules at the interface can vary; a preferential adsorption of different molecules can also occur.