STUDY ON THE SELF-ASSOCIATION OF ASPHALTENES AND THEIR INTERACTION WITH RESINS BY CALORIMETRY

摘要

The self-association of asphaltenes has been investigated by Isothermal Titration Calorimetry. According to the experiments carried out, the hypothesis of having a Critical Micellar Concentration is no longer valid for this system, and the self-association of asphaltenes seems to be step-wise. The low concentration region (<1 g/1) was thoroughly studied and the results obtained point at the direction of having association of asphaltenes at very low concentrations. Fluorescence spectroscopy has also been used to validate the conclusions obtained by calorimetry. The influence of water has also been investigated. The solubility of water in toluene is very small (0.047% weight at 20°C). In the past, it had been claimed that these traces of water had a great influence in the self-association of asphaltenes. However, in latest calorimetric experiments we cannot see this influence. The main objective of the project is to characterize the interaction of resins and asphaltenes: enthalpy of interaction, average number of sites available for resin bonding in an asphaltene molecule and also the role of water in the resin-asphaltene micelle.