High-Field (3.4 T) Electron Paramagnetic Resonance, 1H Electron-Nuclear Double Resonance, ESEEM, HYSCORE, and Relaxation Studies of Asphaltene Solubility Fractions of Bitumen for Structural Characterization of Intrinsic Carbon-Centered Radicals

Abstract

Petroleum asphaltenes are considered the most irritating components of various oil systems, complicating the extraction, transportation, and processing of hydrocarbons. Despite the fact that the paramagnetic properties of asphaltenes and their aggregates have been studied since the 1950s, there is still no clear understanding of the structure of stable paramagnetic centers in petroleum systems. The paper considers the possibilities of various electron paramagnetic resonance (EPR) techniques to study petroleum asphaltenes and their solubility fractions using a carbon-centered stable free radical (FR) as an intrinsic probe. The dilution of asphaltenes with deuterated toluene made it possible to refine the change in the structure at the initial stage of asphaltene disaggregation. From the measurements of samples of bitumen, a planar circumcoronene-like model of FR structure and FR-centered asphaltenes is proposed. The results show that EPR-based approaches can serve as sensitive numerical tools to follow asphaltenes’ structure and their disaggregation.

Resin–Paraffin Aggregation Processes in Waxy Oil Revealed by Vanadyl Porphyrin Spin Probe

“…Currently, a number of methods are being developed that allow obtaining information about the structure, dynamics, and local environment of heavy components in oils at the atomic and molecular level, among which spectroscopic (FTIR spectroscopy, ,, small-angle scattering (SAS), − and dynamic light scattering (DLS)) , and resonance (NMR and electron spin resonance (ESR)) ,− methods can be distinguished. Each of these methods has advantages and limitations.…”