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Structural characterization studies have been carried out on four commercial Saudi Arabian crude oils. The aromaticity and crystallite parameters of the asphaltenes were studied by X-ray diffraction methods and compared to the average structural parameters calculated from nuclear magnetic resonance spectra.

This study reports the isolation and characterization of nickel and vanadyl porphyrins in the residue (535 °C+) and asphaltenes from Arabian Heavy crude oil. The residue was obtained by distillation of crude oil, whereas the asphaltenes were precipitated by rc-heptane from the crude oil. Metalloporphyrins were first extracted from the residue and the asphaltenes. The nickel porphyrins were separated from vanadyl porphyrins by means of adsorption chromatography on silica gel and alumina using solvents of increasing polarity. The chromatographic separation process was monitored by ultraviolet-visible spectrophotometry. Both nickel and vanadyl porphyrins were identified and characterized by ultraviolet-visible spectrophotometry and mass spectrometry.been fully or partially established. Types of these porphyrins and their structures are also listed.

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