Structural Features of Boscan and Duri Asphaltenes

The molecular structural units of Boscan and Duri asphaltenes have been investigated in ruthenium-ion-catalyzed oxidation (RICO) and pyrolysis. From the RICO reactions, homologous series of n-alkanoic acids (C1−C31), representing aromatic-attached n-alkyl side chains, α,ω-di-n-alkanoic acids (C4−C26), representing polymethylene bridges connecting two aromatic units, and benzenecarboxylic acids, indicating the major modes of aromatic condensations in the asphaltene molecules and the minor role of pericondensed aromatic structures in them, were detected and measured. The RICO reaction also yielded a nondistillable oxidized residue. Pyrolysis of this material after methylation yielded a homologous series of n-alkanes and n-alk-1-enes, n-alkanoic and n-alkenoic acid methyl esters, and free n-alkanoic acids with strong even-to-odd carbon preference. These products prove the presence of naphthenic-attached n-alkyl side chains and bridges, polymethylene bridges connecting aromatic to naphthenic systems, and n-al...