A gemini ionic liquid and its low-temperature demulsification performance in water-in-crude oil emulsions

Abstract

In the demulsification process of crude oil emulsions, the temperatures of above 60 °C are most commonly required. In this work, a gemini ionic liquid (PGE-TFA) with amphipathy and interfacial activity was prepared by a simple and safe method, which could be used at the temperature of 40 °C for the effective demulsification of crude oil emulsions. The chemical structure and thermostability was investigated by FTIR, 1HNMR and TGA. The demulsification tests of PGE-TFA showed that it had higher demulsification efficiency (DE) and faster demulsification rate than common commercial demulsifiers. PGE-TFA could be used at a low temperature of 40 °C, a wide pH range and high salinity. The DE reached as high as 95.53 % in water-in-oil emulsions with the concentration of 500 mg/L at 40 °C for 90 min. The temperature of 70 °C could slightly increase the DE and significantly improve the demulsification rate, and the DE of 97.72 % was obtained with the same concentration for 30 min. In addition, the demulsification mechanism was investigated by dynamic interfacial tension, competitive adsorption and zeta potential. The results displayed that PGE-TFA had amphipathy and interfacial activity, which promoted it quickly diffuse to the oil-water interface and displace asphaltenes at the interface. Therefore, an unstable composite film could be formed at the interface and the interfacial tension was lowered, which induced the demulsification of the emulsions.