Acid—base characteristics of petroleum asphaltenes as studied by non-aqueous potentiometric titrations

Abstract

This Paper describes the determination of acids and bases present in petroleum asphaltenes by differential non-aqueous potentiometric titrations. The acids and bases are split into differing pKa's by addition of model compounds. Structural information about the nature of the groups titrated was obtained from the study of many model systems. The strong, medium and weak acids titrated are due to the presence of carboxylic, phenolic and indolic functionality, respectively, whereas the strong bases titrated are due to pyridine groups, the medium strength bases due to pyrazines and sulphoxides and the very weak bases due to indoles and amides.