Asphaltenes: Structural characterization, self-association, and stability behavior

The influence of different factors on the asphaltene stability in four crud e oils was evaluated. Compositional studies and structural characterization of resins and asphaltenes were carried out in order to study a possible re lationship between these properties and the asphaltene deposition behavior. Low hydrogen-to-carbon ratios, high aromaticities, and high condensation o f aromatic rings were the main characteristics of the asphaltenes from unst able crude oils. According to these results, the stability behavior of the crude oils studied was strongly influenced by the structural characteristic s of their asphaltenes, Since the self-aggregation of asphaltenes is a firs t step in the formation of precipitated asphaltene particles, this study al so evaluates the formation of asphaltene aggregates as a function of the st ructural characteristics of the asphaltenes. The self-aggregation behavior was studied on the basis of surface tension measurements. Critical micelle concentrations were determined in different solvents. Using these results, it was possible to establish a relationship between self-association and st ructural characteristics through the calculation of the Flory parameter. On the basis of these findings, different characteristic patterns were identi fied depending on the origin of the asphaltenes. A new correlation has been found to describe the critical micelle concentrations of the asphaltene so lutions.