Influence of Co-based catalyst on subfractional composition of heavy oil asphaltenes during aquathermolysis

Abstract

© 2019 Elsevier B.V. The chemical changes in the composition of asphaltene subfractions of heavy oil under the influence of oil-soluble Co-based catalyst were investigated. The results of SARA-analysis and MALDI-spectroscopy revealed a decrease in absolute content of asphaltenes and their molecular masses in the presence of catalyst. Moreover, the sulfur content was decreased under the catalyst influence and it was mostly observed in the subfraction with the highest molecular weight (A5). The main catalytic reaction was a destructive hydrogenation, directed to break the –С–S–C– bonds in the asphaltene molecules. The 13C NMR spectra revealed the decrease in average length of chain (MCL) after catalytic treatment by 15 times in A1 subfraction, which was accepted as a solvate layer and almost by 13 times in A2 subfraction. The C–O and C–S bonds break in the side chains of aromatic and alicyclic hydrocarbons. The content of primary (Cp) and the sum of secondary and quaternary (Csq) carbons was increased, while the content of tertiary (Ct) and aromatic carbons (Car) declined. The high-molecular poly-alicyclic and polyaromatic components had lost the straight and branched aliphatic hydrocarbons, and then were transformed into coke like substance – carbene-carboids.