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The differences in the chemical structures of the asphaltene fractions present in a vacuum residue feed and in product oil after mild thermal processing, in the presence of N2 and H2 gases (activation gases), was studied using measurements of molecular weight, elemental analysis, nuclear magnetic resonance (NMR) spectroscopy, and X-ray diffraction (XRD). The asphaltene fractions were separated from the feed and product oil according to standard procedures. The percentage intensities of H and C nuclei in different chemical environments were obtained from 1H NMR and 13C NMR spectra of these fractions. The numbers of H atoms and C atoms in various building blocks were thus calculated. The average structural data for the feed and product asphaltene molecules were derived. The macrostructure and aromaticity parameters were determined using XRD and compared with the average structural parameters calculated from NMR. The data show that the aromatic ring structures were similar, although it was the aliphatic structures that made the difference between these fractions.

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