Macrostructure of asphaltenes in vacuum residue by small-angle X-ray scattering

• Published in: Fuel (Guildford) Vol. 72; no. 7; pp. 977 - 981
• Main Authors: Storm, David A., Sheu, Eric Y., DeTar, Maureen M.
• Format: Journal Article
• Language: English
• Published: Oxford Elsevier Ltd 01.07.1993; Elsevier
• Subjects: Applied sciences; asphaltene; Crude oil, natural gas and petroleum products; Energy; Exact sciences and technology; Fuels; Processing of crude oil and oils from shales and tar sands. Processes. Equipment. Refinery and treatment units; residue; X-ray; asphaltene; residue; X-ray; Asphaltene; Small angle X ray scattering; Colloidal state; Chemical structure; Vacuum residue
• ISSN: 0016-2361; 1873-7153
• DOI: 10.1016/0016-2361(93)90295-D

Small-angle X-ray scattering was used to investigate the macrostructure of the asphaltenes (heptane-insolubles) in Duri, Ratawi, Oriente and Merey vacuum residues at 93 °C. Synthetic vacuum residues prepared from these materials with different amounts of asphaltenes were also studied. To determine the shape and average size of the colloidal particles, the measured scattering intensities were fitted by applying the constraint that the contrast must remain independent of shape and size distribution parameters as the asphaltene concentration is varied. According to this analysis the asphaltenic colloidal particles appear spherical. The average radii are in the range 30–60 Å, depending on the crude oil; the radii obey the Schultz distribution. The degree of polydispersity is ~15%. The average particle size does not appear to depend on heteroatom content. Larger asphaltenic particles appear to dissociate when vacuum residue is diluted with the non-asphaltenic fraction.