Some preliminary results on a physico-chemical characterization of a HassiMessaoud petroleum asphaltene

Viscosimetry, tensiometry, and X-ray diffraction have been employed to dete rmine physicochemical and structural properties of an Algerian asphaltene i n solution. A new viscosity analysis scheme was adopted to extract informat ion about the shape of the asphaltene aggregates, the solvation, and the in ter-aggregate interactions. The average molecular weight (MW) was deduced b y combining the surface tension and viscosity studies. The average MW of th is asphaltene appears to be small in comparison with those measured by vapo r pressure osmometry (VPO) but comparable with the recent results from mass spectroscopy, atomic force microscopy, and fluorescent spectroscopy; X-ray measurements show that asphaltene molecules aggregate, even in the neat ph ase, and an average aggregate is composed of 4-5 aromatic sheets. The visco sity study suggests that asphaltenes in toluene solutions behave in accorda nce with a spherical micellar model containing aggregated asphaltene molecu les with a substantial amount of solvation.