Investigating the Stability Mechanism of Water-in-Diluted Bitumen Emulsions through Isolation and Characterization of the Stabilizing Materials at the Interface

Abstract

In oil sand industry, formation of a stable salty water-in-diluted bitumen emulsion poses a serious corrosion problem at the bitumen upgrading plant. Previous studies indicated the presence of a "critical concentration" of bitumen in the emulsion, above which the oil-water interface is flexible and the water-in-diluted bitumen emulsion is stable, but below which the interface becomes rigid and the emulsion is unstable. The cause of this critical concentration was investigated through isolation and characterization of the interfacial material from the emulsions both below and above the critical concentration. The analytical data showed that, in heptane/ toluene(1:1)-diluted bitumen emulsions, the flexible interfacial film is composed of a mixture of asphaltene and carboxylic salts with a combined H/C ratio of 1.32 while the rigid interfacial film is composed of asphaltene alone with a H/C ratio of 1.13. The carboxylic salts are water insoluble and are likely sodium naphthenates containing >20 carbons. The presence of sodium naphthenates might hinder the conformational change of asphaltene at the interface, necessary for rigid film formation.

Fractionation of Asphaltenes in Understanding Their Role in Petroleum Emulsion Stability and Fouling

“…It was reported that rather than whole asphaltenes, only a subfraction of asphaltenes is more likely the real contributor to the stabilization of W/O emulsions. 26,[80][81][82][83][84][85][86] The asphaltenes adsorbed onto clays have also been found to be different in composition from whole asphaltenes. 70,[75][76][77] Therefore, it is important to find ways to extract and study these particular species from asphaltenes, which are mainly responsible for the relevant issues of interest.…”

“…Wu developed an effective method to collect the interfacial materials (IM) of bitumen which adsorb at the surfaces of heavy water (D 2 O) droplets dispersed in the W/O emulsion. 81 In this method, D 2 O was mixed with heptol (a mixture of heptane and toluene at 1:1 volume ratio)-diluted bitumen to form a stable W/O emulsion. Regular deionized (DI) water was then added in the emulsion, followed by the centrifugation of the resulting mixture.…”

Problematic Stabilizing Films in Petroleum Emulsions: Shear Rheological Response of Viscoelastic Asphaltene Films and the Effect on Drop Coalescence

“…Competitive interaction of those species at the water-oil interface has been considered by several researchers, 3,8,9,10 while the introduction of resins has been shown to soften or increase the flexibility of an asphaltene interfacial film. 3,11 When studying micron-sized water drops immersed in diluted bitumen, Wu 12 considered the response of interfacial films to drop volume reduction. At low (solvent:bitumen) dilution ratio, the drop shape was maintained during withdrawal of water, while at high dilution ratio, the interfacial material offered resistance to in-plane shear as observed by drop crumpling.…”

Understanding Mechanisms of Asphaltene Adsorption from Organic Solvent on Mica

“…The interactions and assembly of adsorbed molecules or their aggregates lead to formation of a protective layer that resists droplet-droplet coalescence. [1][2][3][4][5][6][7][8][9][10][11] Stable emulsions have been a major challenge in petroleum production, affecting process throughput and downstream operations such as upgrading. It is necessary to develop knowledge on the formation of these protective layers to design suitable protocols for film disruption and prevention of stable emulsion formation.…”