Structural analysis of the asphaltene fraction of an arabian mixture by a ruthenium-ion-catalyzed oxidation reaction

Ruthenium-ion-catalyzed oxidation (RICO) was used to investigate the structural details of an asphaltene sample. The oxidation products consisted of homologous series of straight- and branched-chain monocarboxylic acids, dominated by C₂-C₄ acids. Aliphatic di- and polycarboxylic acids were also resolved, confirming the presence of polymethylene moieties linking two or more aromatic units. The detection of ethanedioic acid among the oxidation products indicates the importance of biaryl linkages within the asphaltene. Large amounts of a polymeric aliphatic fraction were also recovered after RICO reaction. The recovery of benzene polycarboxylic acids and a high molecular weight aromatic acid fraction, along with NMR analyses of the original asphaltene, indicates that the asphaltene molecule is comprised of relatively large polycondensed aromatics and hydroaromatic units.