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Structural Behavior of Isolated Asphaltene Molecules at the Oil–Water Interface
journal contribution
posted on 2018-07-19, 00:00 authored by Meena
B. Singh, Nakul Rampal, Ateeque MalaniAsphaltenes are the heaviest component
of crude oil, causing the
formation of a stable oil–water emulsion. Even though asphaltenes
are known to behave as an emulsifying agent for emulsion formation,
their arrangement at the oil–water interface is poorly understood.
We investigated the effect of asphaltene structure (island type vs
archipelago type) and heteroatom type (Oxygen-O, Nitrogen-N, and Sulfur-S)
on their structural behavior in the oil–water system. Out of
six asphaltenes studied here, only three asphaltenes remain at the
oil–water interface while others are soluble in the oil phase.
Molecular orientation of asphaltene at the interface, position, and
angle of asphaltene with the interface has also been determined. We
observed that the N-based island type asphaltene is parallel, while
the O-based island type asphaltene and N-based archipelago type are
perpendicular to the interface. These asphaltene molecules are anchored
at the interface by the heteroatom. The S-based asphaltenes (both
island and archipelago type) and O-based archipelago type asphaltenes
are soluble in the oil phase due to their inability to form a hydrogen
bond with water and steric crowding near the heteroatom. This study
will help in understanding the role of asphaltenes in oil–water
emulsion formation based on its structure and how to avoid it.