1 research outputs found
Asphaltene Subfractions Responsible for Stabilizing Water-in-Crude Oil Emulsions. Part 2: Molecular Representations and Molecular Dynamics Simulations
After successful isolation of the
most interfacially active subfraction
of asphaltenes (IAAs) reported in the first part of this series of
publications, comprehensive chemical analyses including ES-MS, elemental
analysis, Fourier transform infrared (FTIR) spectroscopy, and nuclear
magnetic resonance (NMR) spectrometry were used to determine how the
molecular fingerprint features of IAAs are different from those of
the remaining asphaltenes (RAs). Compared with the RAs, the IAA molecules
were shown to have higher molecular weight and higher contents of
heteroatoms (e.g., three times higher oxygen content). The analysis
on the elemental content and FTIR spectroscopy suggested that IAAs
contained higher contents of high-polarity sulfoxide groups than the
RAs. The results of ES-MS, NMR, FTIR, and elemental analyses were
used to construct average molecular representations of IAA and RA
molecules. These structures were used in molecular dynamics (MD) simulation
to study interfacial and aggregation behaviors of the proposed molecules.
The MD simulation study showed little affinity of representative RA
molecules to the oil/water interface, while the representative IAA
molecules had much higher interfacial activity, reflecting the extraction
method. The aggregation of IAA molecules in the bulk oil phase and
their adsorption at oil/water interface were not directly related
to the ring system, but rather to the associations between or including
sulfoxide groups. During the simulation, the IAA molecules were found
to be self-assembled in solvent, forming supramolecular structures
and a porous network at the oil/water interface, as suggested in our
previous work. The results obtained in this study provide a better
understanding of the role of asphaltenes in stabilizing petroleum
emulsions