Asphaltene Adsorption on Functionalized Solids.

Henri-Louis Girard,Dayong Chen,Jessica L Vreeland,Kripa K Varanasi,Aditya Jaishankar,Robert E Cohen,Gareth H Mckinley,Philippe Bourrianne

doi:10.1021/acs.langmuir.0c00029

Henri-Louis Girard, Dayong Chen + Show 6 more

Open Access

https://doi.org/10.1021/acs.langmuir.0c00029

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Abstract

Asphaltenes, heavy aromatic components of crude oil, are known to adsorb on surfaces and can lead to pipe clogging or hinder oil recovery. Because of their multicomponent structure, the details of their interactions with surfaces are complex. We investigate the effect of the physicochemical properties of the substrate on the extent and mechanism of this adsorption. Using wetting measurements, we relate the initial kinetics of deposition to the interfacial energy of the surface. We then quantify the long-term adsorption dynamics using a quartz crystal microbalance and ellipsometry. Finally, we investigate the mechanism and morphology of adsorption with force spectroscopy measurements as a function of surface chemistry. We determine different adsorption regimes differing in orientation, packing density, and initial kinetics on different substrate functionalizations. Specifically, we find that alkane substrates delay the initial monolayer formation, fluorinated surfaces exhibit fast adsorption but low bonding strength, and hydroxyl substrates lead to a different adsorption orientation and a high packing density of the asphaltene layer.

Highlights

Asphaltenes are complex heavy aromatic molecules contained in crude oil and composed of a polyaromatic core and aliphatic side chains.[1−4] This dual morphology is reinforced by the presence of polar substituents in the core such as oxygen, nitrogen, and sulfur[5] and the polarizable nature of the aromatic core.[6]
Despite differences in measurements and in configurations, both quantitative techniques are in good agreement with respect to the trends. Measurements obtained both by the quartz crystal microbalance (QCM) (Figure 3a) and ellipsometry (Figure 3b) show two distinct kinetics depending on the functionalization. On both the hydroxyl and fluorinated substrates, the initial adsorption is rapid: after 1 s, a thickness of 1 nm of asphaltenes is measured by ellipsometry, whereas it remains lower than 1 nm for a few thousands of seconds on the alkane coating
To explain the remaining difference between alkane and fluoroalkane substrates in the steady-state adsorption kinetics observed on the QCM and ellipsometry, the adhesion strength, σ, between a functionalized probe and a layer of asphaltenes adsorbed on a hydroxyl substrate was measured

Summary

Introduction

Asphaltenes are complex heavy aromatic molecules contained in crude oil and composed of a polyaromatic core and aliphatic side chains.[1−4] This dual morphology is reinforced by the presence of polar substituents in the core such as oxygen, nitrogen, and sulfur (see the Supporting Information for elemental composition)[5] and the polarizable nature of the aromatic core.[6]. We investigate the adsorption of a sample of asphaltenes on solid surfaces as a function of the type of interactions they can have with the substrate.

Results

Conclusion