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Asphaltene and Maltene Adsorption into Graphene
journal contribution
posted on 2019-09-19, 15:34 authored by Estrella Rogel, Michael E. Moir, Matthew Hurt, Toni Miao, Eddy LeeIn
this work, the mechanism by which insoluble asphaltenes represented
by small graphene fragments interact with different components of
crude oils is explored. Adsorption isotherms of maltenes and asphaltenes
into graphene from toluene were determined by the depletion method.
The results indicate that the adsorption of these heavy fractions
occurs in two steps: after the initial adsorption, a plateau is reached
that seems to follow a Langmuir type adsorption isotherm. In the second
step, at higher concentrations, the adsorbed amount starts to increase
sharply after an inflection point indicating strong interactions between
the adsorbates. A multilayer adsorption model was successful in describing
this adsorption behavior. Dispersion of graphene in the solution was
observed for some of the samples in the concentration range studied.
It was found that asphaltenes can disperse graphene at lower concentrations
than maltenes. From the same crude oil, it was observed that heptane-extracted
asphaltenes disperse graphene at lower concentrations than the pentane-extracted
ones. Mass spectrometry analysis of the species of molecules left
in the solution after adsorption shows the preferential adsorption
of highly aromatic molecules, high molecular weight molecules, and
molecules containing several heteroatoms. A reduction of 92% on the
relative abundance of porphyrins points to a great affinity of these
species to graphene. These results indicate that graphene-like molecules
in hydrocarbons cannot remain in solution unless they are dispersed
by other components. Therefore, the existence of a critical nanoaggregate
concentration for these crude oil components is unlikely.
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crude oilsadsorption behaviorMaltene Adsorptionadsorption modelinflection pointcrude oil componentsgraphene fragmentsAdsorption isothermsconcentration rangenanoaggregate concentrationporphyrins pointsweight moleculesmass spectrometry analysiscrude oildepletion methodsolutionLangmuir type adsorption isothermheptane-extracted asphaltenesgraphene-like moleculespentane-extracted ones
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