Aggregate structure analysis of colombian heavy crude oil-derived Asphaltenes using small angle X-ray scattering

Abstract

ABSTRACT Small-Angle X-ray Scattering (SAXS) technique was used to characterize the structure of Asphaltene aggregates as a function of its concentration in Toluene solutions. Asphaltene concentration ranged from 0.01 to 1% w/v. Solid Asphaltenes were obtained from a Colombian heavy crude oil following the ASTM D6560-12 standard method by precipitation with n-heptane. Structural properties were interpreted in terms of the radius of gyration (Rg) and the power-law exponents (d). The obtained spectra for Asphaltene-Toluene systems allowed us to explore two regions. At low values of the scattering vector q (q 3 x 10-2), scattering curves showed that Asphaltenes form small dense regions, in which the intensity of the scattered radiation rises with increasing concentration. The observed results demonstrate that Asphaltenes in Toluene solutions coexist as large scale aggregates and nanoaggregates, likewise these structures are conditioned by the Asphaltene concentration and self-association processes.

Keywords

• Colombian Asphaltenes
• Structural properties of aggregates
• Small Angle X-Ray Scattering
• Concentration effect