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 F-19 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).