Asphaltene Chemical Characterization as a Function of Solubility: Effects on Stability and Aggregation

Rather recently, a new technique called the "asphaltene solubility profile" was developed to analyze the stability of asphaltenes. In this technique, a distribution of the asphaltenes in terms of their respective solubilities is provided, allowing for a more comprehensive view of how the different molecules comprising asphaltenes behave and interact. In the present work, maltenes and asphaltenes are preparatively separated according to the classification established by the asphaltene solubility profile analysis, i.e., "transitional material" or easy-to-dissolve asphaltenes (EDA) and difficult-to-dissolve asphaltenes (DDA). The results obtained for blends of DDA and EDA show that the latter fraction has a peptizing effect on the former. EDA help in the solubilization of DDA, as shown by the asphaltene solubility profile of the blends, and also decreases aggregation, as shown by the size-exclusion chromatography experiments. These findings support the following: (a) the idea that this so-called "transitional fraction or EDA" plays a key role in the stabilization of asphaltenes similar to the fraction known as "resins" in the literature, (b) the use of solubility profile analysis as a valid test to evaluate asphaltene stability, and (c) the model of crude oils as a continuum of molecules in which their properties vary gradually.