ELECTRON MICROSCOPIC INVESTIGATIONS ON NATURE OF PETROLEUM ASPHALTICS

An examination of the electron micrographs of four native asphalties, a vanadium-enriched asphaltene, an asphaltene from a visbreaker tar, a resin, and a gilsonite, has revealed in all cases irregular polyhedral shaped particles of average diameter 20-30A. These sizes are similar to the diameters of the aromatic portion of the unit asphaltene cell as estimated from high-angle X-ray studies, suggesting that the associated aliphatic and naphthenic portions of the molecule must be closely bound to the aromatic nucleus. Evidence for particle association into larger clusters was obtained for the vanadium-enriched asphaltene and from the visbreaker tar, and was also noted in samples prepared from concentrated pyridine solutions. The larger particles (150-300A) observed for the vanadium-enriched asphaltene (Boscan), and to some extent for the Boscan asphaltene itself, are thought to be due to the high metal content. Since the smallest particles observed for the native asphaltene are larger than the minimum resolution of the electron microscope, it seems possible that these particles represent the ultimate unit cells of the asphaltenes. © 1969.