Optical Characterization of Asphaltenes at the Air−Water Interface

Abstract

Asphaltenes extracted from Arabian light crude oil have been investigated at the air-water interface of a Langmuir trough by in situ optical techniques. Brewster angle microscopy (BAM) and reflection spectroscopy have been used to extract new information about the microscopic organization of the asphaltene films in terms of association phenomena and chromophore orientation, respectively. The use of different spreading concentrations in the range 0.1-15 mg mL-1 reveals significant changes in the behavior at the interface with more condensed isotherms above 2 mg mL-1. This break point is related to the nanoaggregate-to-cluster association threshold in organic solution widely accepted in the recent asphaltene literature. BAM images support this observation with very different morphologies for the two spreading concentrations employed, 0.1 and 4 mg mL-1, respectively. The study of intensity changes in the corresponding normalized reflection spectra also confirms the transition in the asphaltene interfacial behavior between these two spreading concentrations. Finally, this technique helps with understanding the changes observed in the asphaltene films during a set of compression-decompression cycles.

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.…”

A Geological Model for the Origin of Fluid Compositional Gradients in a Large Saudi Arabian Oilfield: An Investigation by Two-Dimensional Gas Chromatography (GC × GC) and Asphaltene Chemistry

“…22 The nanoaggregate to cluster transition with increasing concentration has also been indicated in interfacial studies. 23 The "island" 1.5 nm molecular architecture depicted in Fig. 2 with a single polycyclic aromatic hydrocarbon (PAH) per molecule previously proposed by time resolved fluorescence polarization studies [24][25] has been confirmed by laser desorption, laser ionization mass spectrometry (L 2 MS).…”

The dynamic Flory-Huggins-Zuo equation of state

“…Nanoaggregates were observed using high-Q ultrasonics [17,18], NMR (nuclear magnetic resonance) [19], DC-conductivity [20,21], SANS (small-angle neutron scattering) and SAXS (small-angle X-ray scattering) [22], and centrifugation [23,24], along with related analysis of gravity gradients in oil reservoirs [25] among other techniques. Clusters were observed by flocculation kinetics [26,27], interfacial studies [28], and DC-conductivity [20].…”