Characterization of Average Molecular Structure of Heavy Oil Fractions by 1H Nuclear Magnetic Resonance and X-ray Diffraction

The chemical structure of heavy oil fractions obtained by liquid-solid adsorption chromatography was characterized by H-1 nuclear magnetic resonance and X-ray diffraction. The molecular weight and molecular formula of asphaltene molecules were estimated by combining H-1 nuclear magnetic resonance and X-ray diffraction analyses, and were also obtained from vapor pressure osmometry and elemental analysis. Heteroatoms, such as S, N, and O atoms, were considered in the construction of average molecular structure of heavy oils. Two important structural parameters were proposed, including the number of alkyl chain substituents to aromatic rings and the number of total rings with heteroatoms. Ultimately, the average molecular structures of polycyclic aromatics, heavy resins and asphaltene molecules were constructed. The number of alpha-, beta-, gamma-, and aromatic hydrogen atoms of the constructed average molecular structures fits well with the number of hydrogen atoms derived from the experimental spectral data.