Dynamic Demulsification Mechanism of Asphaltene-Stabilized Water-in-Oil Emulsions by Ethylcellulose

Abstract

In previous studies, nontoxic and biodegradable ethylcellulose (EC) was shown to be capable of breaking water-in-diluted bitumen emulsions. Nevertheless, the demulsification mechanism of EC has not been correlated to its effect on the physical properties of stabilizing interfacial asphaltene films. In this study, the effect of EC addition on rheological properties and morphology of heptol diluted asphaltene-water interfacial films was investigated. The adsorption kinetics of asphaltenes and EC at oil-water interface showed that EC was able to compete with the asphaltenes at the interface and fracture the interfacial asphaltene films. The fracture of asphaltene films enhanced coalescence and dewatering, as confirmed in demulsification bottle test and droplet-droplet coalescence time experiment. The shear and compressional rheology measurements revealed that EC could significantly soften asphaltene films formed at oil-water interface, most likely as a result of disruption of the asphaltene films network as observed with Brewster angle microscopy. In conclusion, EC was proven to soften and break the asphaltene films at the oil-water interface, promoting the coalescence of water droplets and emulsion dewatering.