CHARACTERIZATION OF ASPHALTENE AGGREGATES WITH SMALL ANGLE X-RAY SCATTERING

摘要

The objective of this study is to characterize petroleum asphaltene aggregates in situ with small angle X-ray scattering (SAXS). Asphaltenes were isolated from three different crude oils: Maya (MY), Khafji (KF), and Iranian Light (IL). Quartz capillaries were used to sample 5 mg of asphaltenes. Scattering patterns were obtained on the dry asphaltenes at room temperature under nitrogen flow atmosphere, then the samples were heated up from 30-500°C. Fractal network structures of As-MY and As-IL break at 300°C, while that of As-KF starts to break at lower temperature. As-MY aggregates with the size of around 40 A is stable at upper 300°C, while that of As-KF and As-IL decrease with the increase of the temperature. Considering the molecular structural analysis data of each asphaltenes, it is supposed that aromaticity and hetero functional group of asphaltene molecule contribute to the stability of the fractal network. And the stability of the aggregates with the size of around 40 A may depend on the molecular weight of asphaltene.