Structure, rheology and possible application of water-in-oil emulsions stabilized by asphaltenes

Abstract

Abstract Asphaltenes and resins remaining after heavy crude oil deasphalting (termed asphaltenes) require rational utilization. Due to their surface activity, such utilization can consist in obtaining and stabilizing water-in-oil emulsions. In this study, several series of emulsions were obtained using di(2-ethylhexyl) sebacate as a continuous phase and water or saturated aqueous solutions of various compounds (urea, NH4NO3, KH2PO4, CH3COONa) as a disperse phase. Asphaltenes were unlimitedly soluble in ester oil and could form dilute, semi-dilute, and concentrated solutions whose rheology was investigated. Even dilute solutions containing 3–5% of asphaltenes were suitable for obtaining stable emulsions without additional using usual surfactants. The rheology and morphology of emulsions containing from 3% to 15% of asphaltenes and from 15% to 85% of the disperse phase were investigated. The use of asphaltenes as surfactants causes agglomeration of water droplets, which leads to viscoelasticity and viscoplasticity of even dilute emulsions. Replacing pure water with saturated solutions of urea or inorganic salts resulted in the growth of both effective viscosity and yield stress of emulsions without radical changes in their rheology. Such emulsions can be potentially used as liquid fertilizers, explosives, or heat accumulators.