Molecular View of the Asphaltene Aggregation Behavior in Asphaltene−Resin Mixtures

The aggregation behavior of asphaltenes in asphaltene−resin mixtures within different host media is studied on the basis of the asphaltene/resin molecular structures and considering the embedding medium as a uniform background field. The approach employs models of molecular structures for both asphaltenes and resins (as derived from characterization data), and uses Molecular Mechanics (MM)/Molecular Dynamics (MD) calculations to predict the effect of the intermolecular interactions on the aggregation process as a function of composition and embedding medium. The peptizing behavior of resins is analyzed as a function of the ratio of resin to asphaltene molecules in each host medium by constructing the corresponding MD-generated radial distribution functions as well as the associated potentials of mean force (PMF). In all cases, the PMF presents repulsive barriers characteristic of aggregate systems showing a strong aggregation effect in a highly precipitant medium such as heptane. For an intermediate preci...