PACKING OF ASPHALTENE PARTICLES – AN EXPLANATION OF CHANGES IN SOLUTION PROPERTIES?

Simon Ivar Andersen

Center for Phase Equilibria and Separation Processes

Dept.Chem.Eng. bldg. 229

Technical University of Denmark

DK-2800 Kgs.Lyngby

Denmark

The steps from monomeric to associated and flocculated asphaltenes have been investigated thoroughly through decades. Recently (Merino-Garcia and Andersen, 2004) the mechanism of critical micellization was rejected using state-of-the-art isothermal titration calorimetry and a step-wise association was proposed at least for concentrations of asphaltenes above ca. 50 ppm in toluene.

Data on aggregation, flocculation onset, surface tension, calorimetry, Size exclusion chromatography etc. as a function of concentration all indicate changes in the vicinity of 5 g/l in toluene, and beyond this value magnitudes are fairly constant.  Data from the literature including SANS and dielectric spectroscopy is included into an explanation of this change based on repulsive forces between colloidal particles – hence an alternative explanation to the “critical micelle concentration” mechanism popular since the 1980´es will be presented. This approach uses the assumption that over a concentration range a limiting growth mechanism exists