Asphaltene Behavior at Interfaces

Abstract

The interfacial behavior of asphaltene samples, obtained from two different sources, was studied by means of Langmuir balance and Brewster angle microscopy (BAM) at the air/water interface. Transferred films from the air/water interface on mica were studied by atomic force microscopy (AFM). Isotherms obtained from the Langmuir balance experiments for all samples are qualitatively similar and indicate that their interfacial behavior may be correlated to the molecular weight of the asphaltene samples. At mesoscopic scales, BAM images of asphaltene films deposited on the water surface reveal that asphaltene samples do not form a monomolecular film, as proposed in the literature, but rather a mixture of 2D and 3D domains. This behavior is confirmed when, on a hydrophilic surface such as mica, the film is transferred from the Langmuir trough and is found to be not homogeneous or monomolecular. AFM images revealed the formation of an irregular and meandering layer of 10.2−12.5 nm thickness. Initially, the films exhibit some mesostructures graphically identified as small and large disklike structures; these disks coalesce or fuse into more complex mesostructures: drumsticklike and ribbonlike structures. A closer look revealed that these mesostructures are formed by small colloidal-like particles or small micelles (<100 nm). The spreading capacity of asphaltene on the mica surface seems to be related to the separation methods and the amount of resins associated with the asphaltenes. The complete coverage of the surface and the formation of an irregular 3D film occur as a function of aging time or when the transference pressure of the asphaltene film from water to mica is increased.

Demulsification Mechanism of Asphaltene-Stabilized Water-in-Oil Emulsions by a Polymeric Ethylene Oxide–Propylene Oxide Demulsifier

“…5), in agreement with previously published data [60][61][62] . In previous studies the morphology of asphaltene films was probed in situ with BAM at the air-water interface 41,[60][61][62] , while asphaltenes films at the toluene-water interface have been previously imaged after being transferred onto solid substrates (LB films) 55,57,63 . In the current study, after the toluene (good solvent) top phase was gently added, the cracks in the film were observed to "heal" (Fig.…”

Insights into asphaltene aggregation in the Na-montmorillonite interlayer

“…6A). Such structure was previously observed by Cadena-Nava et al (2007) and was attributed to the dipole-dipole and hydrophobic interactions on the hydrophilic mineral surface. By contrast, the LHA samples were widely spread on the mica surface without clusters developed in the vertical direction except only a few small peaks were noted (Fig.…”

“…Progresses have also been made on characterizing the adsorption of asphaltenes on mineral surface (Cadena-Nava et al, 2007), but it remains unclear about the effects of factors such as the pore water content, salinity and interlayer space on the aggregation of asphaltenes in the clay pore. This fundamental knowledge is essential for better understanding the persistence of the residual oil in the contaminated soils after long-term ageing.…”

Combined interfacial shear rheology and microstructure visualization of asphaltenes at air-water and oil-water interfaces

“…In the last two decades, the interfacial viscoelasticity of asphaltenes have been studied, including air-water [15,[22][23][24][25][26][27][28][29][30][31] and oil-water interfaces with either air [32][33][34][35] or oil induced aggregation [14,[36][37][38][39][40][41][42][43] as well as oil-water interfaces with asphaltenes in the dispersed phase [43][44][45]. These studies have shown that the conditions by which the asphaltene film forms at the interface determine its rheological responses.…”