Intermolecular Magnetic Spin-Spin Interaction in Asphaltene Suspensions at 1.53 mT

Abstract

In this study, Overhauser effect (OE) type of dynamic nuclear polarization (DNP) experiments were performed to study suspensions of MC800 asphaltene in bromopentafluorobenzene, chloropentafluorobenzene and hexafluorobenzene aromatic solvents. The experiments were performed at a low field of 1.53 mT in a double-resonance nuclear magnetic resonance (NMR) spectrometer. In this technique the nuclei of diffusing solvent molecules and the unpaired electron existing on the asphaltene micelles interact magnetically. The DNP parameters were determined. Additionally, the interactions between 19 F nuclei of the solvent and the electrons delocalized on the asphaltene are interpreted. The highest enhancement factor value (5.90) was obtained for the hexafluorobenzene solvent medium, because between these, hexafluorobenzene has the highest fluorine atom number. The solvent molecules attach to the colloidal asphaltene particles for a very short time forming complexes and making scalar interaction. Morphologies of asphaltene surfaces depending on the solvent effects were observed by using scanning electron microscopy (SEM).

Suppression of Phase Separation as a Hypothesis to Account for Nuclei or Nanoaggregate Formation by Asphaltenes in Toluene

“…For decades, the aforementioned phase separation was confused with “inverse micelle” formation because of its similarities with the behavior of surfactants in oily media. This confusion has made the term “asphaltene micelle” common in the past as well as in recent years. − The references cited here are only a small sample of the many published articles that mention asphaltene micelles, which, according to Science Direct, is approximately 1200 papers over the course of 40 years and approximately 200 papers in the last two years. In the case of surfactants in an oily medium, however, aggregation may occur via the stepwise formation of multimers .…”