Direct Observation of Asphaltene Nanoparticles on Model Mineral Substrates

Gijo Raj, Alain Lesimple, Jamie Whelan, Pance Naumov

    Research output: Contribution to journalArticle

    Abstract

    The propensity for adherence to solid surfaces of asphaltenes, a complex solubility class of heteropolycyclic aromatic compounds from the heavy fraction of crude oil, has long been the root cause of scale deposition and remains an intractable problem in the petroleum industry. Although the adhesion is essential to understanding the process of asphaltene deposition, the relationship between the conformation of asphaltene molecules on mineral substrates and its impact on adhesion and mechanical properties of the deposits is not completely understood. To rationalize the primary processes in the process of organic scale deposition, here we use atomic force microscopy (AFM) to visualize the morphology of petroleum asphaltenes deposited on model mineral substrates. High imaging contrast was achieved by the differential adhesion of the tip between asphaltenes and the mineral substrate. While asphaltenes form smooth continuous films on all substrates at higher concentrations, they deposit as individual nanoparticles at lower concentrations. The size, shape, and spatial distribution of the nanoaggregates are strongly affected by the nature of the substrate; while uniformly distributed spherical particles are formed on highly polar and hydrophilic substrates (mica), irregular islands and thicker patches are observed with substrates of lower polarity (silica and calcite). Asphaltene nanoparticles flatten when adsorbed on highly oriented pyrolytic graphite due to π-π interactions with the polycyclic core. Force-distance profiles provide direct evidence of the conformational changes of asphaltene molecules on hydrophilic/hydrophobic substrates that result in dramatic changes in adhesion and mechanical properties of asphaltene deposits. Such an understanding of the nature of adhesion and mechanical properties tuned by surface properties, on the level of asphaltene nanoaggregates, would contribute to the design of efficient asphaltene inhibitors for preventing asphaltene fouling on targeted surfaces. Unlike flat surfaces, the AFM phase contrast images of defected calcite surfaces show that asphaltenes form continuous deposits to fill the recesses, and this process could trigger the onset for asphaltene deposition.

    Original languageEnglish (US)
    Pages (from-to)6248-6257
    Number of pages10
    JournalLangmuir
    Volume33
    Issue number25
    DOIs
    StatePublished - Jun 27 2017

    Fingerprint

    Minerals
    asphaltenes
    Asphaltenes
    minerals
    Nanoparticles
    nanoparticles
    Substrates
    adhesion
    Adhesion
    Deposits
    crude oil
    deposits
    Calcite
    mechanical properties
    Calcium Carbonate
    calcite
    Petroleum
    Mechanical properties
    Atomic force microscopy
    Crude oil

    ASJC Scopus subject areas

    • Materials Science(all)
    • Condensed Matter Physics
    • Surfaces and Interfaces
    • Spectroscopy
    • Electrochemistry

    Cite this

    Direct Observation of Asphaltene Nanoparticles on Model Mineral Substrates. / Raj, Gijo; Lesimple, Alain; Whelan, Jamie; Naumov, Pance.

    In: Langmuir, Vol. 33, No. 25, 27.06.2017, p. 6248-6257.

    Research output: Contribution to journalArticle

    Raj, G, Lesimple, A, Whelan, J & Naumov, P 2017, 'Direct Observation of Asphaltene Nanoparticles on Model Mineral Substrates', Langmuir, vol. 33, no. 25, pp. 6248-6257. https://doi.org/10.1021/acs.langmuir.7b00866
    Raj, Gijo ; Lesimple, Alain ; Whelan, Jamie ; Naumov, Pance. / Direct Observation of Asphaltene Nanoparticles on Model Mineral Substrates. In: Langmuir. 2017 ; Vol. 33, No. 25. pp. 6248-6257.
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