Colloidal Stability of Bitumens Related to their Generic Composition

Three bitumens obtained from crude oils widely differing in chemical nature were analyzed for generic composition. Separation into group components was carried out by liquid chromatography, using a new procedure. With this method, five fractions were separated, i.e. saturates, cyclics, light resins, heavy resins and asphaltenes. The size distribution of the asphaltene particles in the bitumens and the Heithaus parameters characterizing the colloidal stability of bitumen were determined. The results suggest that the role of the light resins in bitumen differs from that of the heavy resins, as they are constituents of the dispersing and dispersed phase, respectively. The cyclic components and light resins form the dispersing medium of bitumen while the heavy resins and asphaltenes constitute the dispersed material. Saturates are the bitumen components that deteriorate the peptization of asphaltene particles.