6 research outputs found
Molecular Dynamics Simulation of Self-Aggregation of Asphaltenes at an Oil/Water Interface: Formation and Destruction of the Asphaltene Protective Film
It is well known that asphaltene
molecules play a significant role
in stabilizing emulsions of water in crude oil or diluted bitumen
solutions. Molecular dynamics simulations were employed to investigate
the aggregation and orientation behaviors of asphaltene molecules
in a vacuum and at various water surfaces. Two different continental
model asphaltene molecules were employed in this work. It was found
that the initially disordered asphaltenes quickly self-assembled into
ordered nanoaggregates consisting of several molecules, in which
the aromatic rings in asphaltenes were reoriented to form a face-to-face
stacked structure. More importantly, statistical analysis indicates
that most of the stacked polycyclic aromatic planes of asphaltene
nanoaggregates tend to be perpendicular to the water surface.
If the asphaltene molecules are considered as “stakes”,
then the asphaltene nanoaggregate can be regarded as a “fence”.
All the fence-like nanoaggregates were twined and knitted together,
which pinned them perpendicularly on the water surface to form a steady
protective film wrapping the water droplets. The mechanism of stabilization
of the water/oil emulsions is thereby well understood. Demulsification
processes using a chemical demulsifier were also studied. It was observed
that the asphaltene protective film was destroyed by a demulsifier
of ethyl cellulose molecules, leading to exposure of the water droplet.
The results obtained in this work will be of significance in guiding
the development of demulsification technology
Molecular Dynamics Simulation of Self-Aggregation of Asphaltenes at an Oil/Water Interface: Formation and Destruction of the Asphaltene Protective Film
It is well known that asphaltene
molecules play a significant role
in stabilizing emulsions of water in crude oil or diluted bitumen
solutions. Molecular dynamics simulations were employed to investigate
the aggregation and orientation behaviors of asphaltene molecules
in a vacuum and at various water surfaces. Two different continental
model asphaltene molecules were employed in this work. It was found
that the initially disordered asphaltenes quickly self-assembled into
ordered nanoaggregates consisting of several molecules, in which
the aromatic rings in asphaltenes were reoriented to form a face-to-face
stacked structure. More importantly, statistical analysis indicates
that most of the stacked polycyclic aromatic planes of asphaltene
nanoaggregates tend to be perpendicular to the water surface.
If the asphaltene molecules are considered as “stakes”,
then the asphaltene nanoaggregate can be regarded as a “fence”.
All the fence-like nanoaggregates were twined and knitted together,
which pinned them perpendicularly on the water surface to form a steady
protective film wrapping the water droplets. The mechanism of stabilization
of the water/oil emulsions is thereby well understood. Demulsification
processes using a chemical demulsifier were also studied. It was observed
that the asphaltene protective film was destroyed by a demulsifier
of ethyl cellulose molecules, leading to exposure of the water droplet.
The results obtained in this work will be of significance in guiding
the development of demulsification technology
Functionalized carbon black nanoparticles used for separation of emulsified oil from oily wastewater
<p>Functionalized carbon black (F-CB) nanoparticles were synthesized by covalently grafting the polyvinyl alcohol on carbon black (CB) surfaces and used as demulsifier to separate the oil from the emulsified oily wastewater. The bottle test showed that the residual oil content in the separated water was as low as ∼50 mg/L corresponding to a demulsification efficiency of about 99.90% at an optimal condition within a few minutes. It was believed that the surface wettability of the carbon black could be tuned by modifying with the PVA molecules, which enables the F-CB nanoparticles to be readily migrated to the oil/water interface and have the opportunity to interact with and/or displace the stabilizers of the emulsion. As a result, the demulsification process was accomplished with the coalescence of the oil droplets promoted by the F-CB nanoparticles. The interaction behavior between F-CB nanoparticles and asphaltenes was investigated by quantum chemical calculations. The results showed that the F-CB nanoparticles have strong interaction with the asphaltene molecules in form of π−π and θ−π forces. The findings in present study are significant for understanding the demulsification mechanism and also provide a novel demulsifier for the demulsification of emulsified oily wastewater.</p
Revealing the Intermolecular Interactions of Asphaltene Dimers by Quantum Chemical Calculations
Understanding
the nature of non-covalent interactions (NCIs) between
asphaltene molecules is not only theoretically interesting but also
important for practical application. We performed quantum chemical
calculations to reveal the configuration feature and intermolecular
interaction characteristics of asphaltene dimers using three representative
asphaltene model compounds and their derivatives. The frontier molecular
orbitals and electrostatic potential map of the model asphaltenes
were analyzed to reveal the nature of interaction between the asphaltene
monomers. The calculation of binding energies indicates that the stability
of asphaltene dimers not only depends upon the number of aromatic
rings but also relies on the presence of heteroatoms in the aromatic
core and aliphatic side chains, which could change the electrostatic
charge distribution on the molecular van der Waals surface. In addition,
NCIs and the natural bond order analysis method were used to identify
the interactions that promote the formation of asphaltene dimers.
It was found that the reduced density gradient isosurfaces could clearly
reveal the type of interactions between two asphaltene monomers in
their dimers. The results indicate that various interactions possess
either an electrostatic or a dispersive nature, including hydrogen-bonding,
θ–θ, θ–π, and π–π
interactions, among which the π–π stacking interaction
is believed to be the major driving force for asphaltene aggregation
Demulsification of Crude Oil-in-Water Emulsions Driven by Graphene Oxide Nanosheets
Seeking highly efficient, rapid,
universal, and low-cost demulsification
materials to break up the crude/heavy oil-in-water emulsion and emulsified
oily wastewater at ambient conditions has been the goal of the petroleum
industry. In this work, an amphiphilic material, graphene oxide (GO)
nanosheets, was introduced as a versatile demulsifier to break up
the oil-in-water emulsion at room temperature. It was encouraging
to find that the small oil droplets in the emulsion quickly coalesced
to form the oil phase and separated with the water within a few minutes.
The demulsification tests indicated that the residual oil in separated
water samples was as low as ∼30 mg/L, corresponding to a demulsification
efficiency over 99.9% at an optimum GO dosage. More importantly, GO
not only is useful for ordinary crude oil emulsion but also can be
used to break up the extra heavy oil emulsion. The effect of the emulsion
pH on the demulsification was also investigated. It was interesting
to find that the distribution of GO either in oil or in water phase
after demulsification was dependent on the pH value of the solution,
which was attributed to the pH-dependent amphiphilicity of GO. The
prominent demulsification ability of GO was attributed to the strong
adsorption between the GO nanosheets and molecules of asphaltenes/resins
driven by π–π interactions and/or n−π
interactions. The findings in this work indicate that the GO nanosheets
are a simple, highly efficient, and universal demulsifier to separate
the oil from the crude/heavy oil-in-water emulsions at ambient conditions,
which shows a good application prospect in the oil industry
Demulsification of Crude Oil-in-Water Emulsions Driven by Graphene Oxide Nanosheets
Seeking highly efficient, rapid,
universal, and low-cost demulsification
materials to break up the crude/heavy oil-in-water emulsion and emulsified
oily wastewater at ambient conditions has been the goal of the petroleum
industry. In this work, an amphiphilic material, graphene oxide (GO)
nanosheets, was introduced as a versatile demulsifier to break up
the oil-in-water emulsion at room temperature. It was encouraging
to find that the small oil droplets in the emulsion quickly coalesced
to form the oil phase and separated with the water within a few minutes.
The demulsification tests indicated that the residual oil in separated
water samples was as low as ∼30 mg/L, corresponding to a demulsification
efficiency over 99.9% at an optimum GO dosage. More importantly, GO
not only is useful for ordinary crude oil emulsion but also can be
used to break up the extra heavy oil emulsion. The effect of the emulsion
pH on the demulsification was also investigated. It was interesting
to find that the distribution of GO either in oil or in water phase
after demulsification was dependent on the pH value of the solution,
which was attributed to the pH-dependent amphiphilicity of GO. The
prominent demulsification ability of GO was attributed to the strong
adsorption between the GO nanosheets and molecules of asphaltenes/resins
driven by π–π interactions and/or n−π
interactions. The findings in this work indicate that the GO nanosheets
are a simple, highly efficient, and universal demulsifier to separate
the oil from the crude/heavy oil-in-water emulsions at ambient conditions,
which shows a good application prospect in the oil industry