Brewster Angle Microscopy of Langmuir Films of Athabasca Bitumens, n-C5 Asphaltenes, and SAGD Bitumen during Pressure–Area Hysteresis

Abstract

Bitumen films formed on water surfaces have negative consequences, both environmental and economic. CanmetENERGY has placed considerable research emphasis on understanding the structures of the bitumen films on water as a necessary step before optimization of bitumen extraction. The detailed structures of the adsorbed molecules and, especially, the role of asphaltene molecules at the interfaces are still under scrutiny and debate. In the present study, we compared bitumen and asphaltene films as they were compressed and expanded under various surface pressures in order to achieve a clearer understanding of bitumen film structures. We used a customized NIMA Langmuir trough interfaced to a Brewster angle microscope (BAM) and CCD camera (Nanofilm_ep3BAM, Accurion, previously Nanofilm Gmbh) to study images of bitumen films at the air/water interface. The bitumen film appeared uniform with high reflectivity at a surface pressure of 18 mN·m(-1) and exhibited a coarse pebblelike interface with reduced reflectivity in the liquid condensed (LC) phase at higher pressures (18-35 mN·m(-1)). During the first cycle of compression asphaltene films showed well-defined phase transitions and a uniformly smooth interface in the LC phase between 9 and 35 mN·m(-1). However, folding or buckling occurred at surface pressures from 35 to 44 mN·m(-1). On expansion, asphaltene films appeared to break into islands. The hysteresis of the pressure-area isotherm was much larger for asphaltenes than for bitumen. In both compression and expansion cycles, BAM images for bitumen films appeared to be more reproducible than those of the asphaltene films at the same surface pressures. Films for low-°API SAGD bitumen were almost identical to those for surface-mined bitumen. Films formed from partially deasphalted surface-mined bitumens showed higher compressibility and lower rigidity than the original bitumen. The BAM images illustrated significant differences between the partially deasphalted and original bitumen films. Other components in bitumen also played important roles in determining the interfacial properties of bitumen films.

Mixed Interfaces of Asphaltenes and Model Demulsifiers, Part II: Study of Desorption Mechanisms at Liquid/Liquid Interfaces

“…Furthermore, interfacial dilatational rheology was used to couple these results with features related to the elasticity of the film formed at the liquid-liquid interface. Asphaltene desorption has been traditionally studied at the solid-air or liquid-air interfaces through Langmuir trough, Langmuir-Blodgett films (LB), Brewster angle microscopy (BAM) 4,13,15,[64][65][66] and quartz crystal microbalance technique 4,67,68 . In this work, a study at the liquid-liquid interface is proposed.…”

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.…”

“…Type I behaviour has been reported for EC 31 and for some EO-PO demulsifiers 27,[32][33][34] , while overdose was observed for octylphenylpolyethoxylates and sodium bis(2-ethylhexyl)sulfosuccinate demulsifiers 35 , commercial demulsifiers [36][37][38] , polyoxyalkylates 9 , diethanolamines 15 and some EO-PO demulsifiers 27,39 . These demulsifiers act either as flocculants or coalescers 41 . Overdose for flocculating demulsifiers, such as polyoxyalkylates 9 and diethanolamines 15 , was attributed to the low density of formed flocs 9 as a result of electrosteric repulsion 15 .…”

“…Studies relating emulsion stability to the mechanical properties and morphology of asphaltene interfacial films are very limited and have only been conducted at the air-water interface 40,41 .…”

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

“…This leads to flow assurance problems, such as difficulty in transporting highly viscous fluids or separating phases in stabilized water-in-oil emulsions [13,14]. Furthermore, tailings/wastewater containing bitumen and crude oil that are discharged into tailing ponds often deposit and form a film on the pond [15,16]. Therefore, understanding of the interfacial properties of the surface-active species in the oil is essential for recovery and remediation of oils.…”