Aggregation of tetrameric acid in xylene and its interaction with asphaltenes by isothermal titration calorimetry

Abstract

This paper describes the self-association of tetrameric acids (TA) and their interactions with asphaltenes using isothermal titration calorimetry. In order to visualize the importance of molecular structures of TA and asphaltenes, stearic acid (SA) and asphaltene model compounds are used for comparison. Both SA and TA form dimers in xylene solutions. However, the dimerization enthalpy for SA (ΔH) in absolute value is higher than the corresponding value for TA, indicating that the aggregation is less efficient for TA likely due to steric reasons. The interplay between asphaltenes and TA or SA is similar except at low concentrations. Interactions between TA and asphaltene model compounds are strongly dependent on the presence of acid group in model compounds, indicating hydrogen bonds as a central but not only element in the interactions.