Role of Resins on Asphaltene Stability

The objective of this study is to clarify through impedance analysis some of the controversial issues related to the role of resins on asphaltene stability. From the variations of the direct-current (DC) conductivity of charge carriers in petroleum fluids with their concentration in toluene, we find that resins are unlikely to coat asphaltene nanoaggregates within the concentration range investigated (10−1000 ppm). Thus, the long-time-standing Nellensteyn hypothetical model, where resins adsorb on asphaltenes to provide a steric stabilizing layer, is not valid. In heptane/toluene mixtures, the least soluble resins tend to aggregate with asphaltenes to enhance their stability in the mixture, in agreement with a recently proposed molecular thermodynamic approach to the formation of mixed asphaltene−resin aggregates ( Rogel, E. Molecular thermodynamic approach to the formation of mixed asphaltene−resin aggregates Energy Fuels 2008, 22 (6), 3922−3929).