Synthesis of a low temperature ionic liquid demulsifier and its demulsification mechanism

In this paper, an ionic liquid (DEBIL) was synthesized by a simple and controllable method. The chemical structure was verified by FT-IR, 1 H NMR and 13 C NMR, and the demulsification performance was observed by the bottle test. The results displayed that DEBIL had faster demulsification rate and higher demulsification efficiency (DE) than commercial demulsifiers. In addition, its production cost is lower than existing commercial demulsifiers which usually use ethylene oxide and propylene oxide as starting materials. In detail, the DE could reach 98.5 % after demulsifying with 300 mg/L of DEBIL for 2 h at 50 °C. Besides, DEBIL had a DE of greater than 95 % at high salinities (50000 mg/L), low temperature (40 °C), and wide pH range (2–10). Moreover, interfacial competitive adsorption between asphaltene and DEBIL was observed by the interfacial tension (IFT), three-phase contact angle (CA), coalescence time of droplets and elastic modulus of interfacial film. Furthermore, the possible demulsification mechanism was proposed in this study. DEBIL has both hydrophilic center and hydrophobic alkyl chains, which enables it to diffuse rapidly to the oil–water interface and reduce the IFT via replacing asphaltenes at the interface, resulting in the formation of unstable composite film and initiating the demulsification.