Demulsification of Heavy Petroleum Emulsion Using Pyridinium Ionic Liquids with Distinct Anion Branching

Abstract

The challenges associated with heavy crude oil emulsions during hydrocarbon exploitation cannot be overemphasized. As such, water/crude oil separation in oil fields becomes necessary before conveyance to the refinery. In this study, we investigated new classes of pyridinium ionic liquids (ILs) demulsifiers, 1-butyl-4-methylpyridinium tetrafluoroborate, 1-butyl-4-methylpyridinium hexafluorophosphate, and 1-butyl-4-methylpyridinium iodide, designated as BMPT, BMPH, and BMPI, with unique anions (BF4–, PF6–, and I–), respectively. The effects of concentration dosages (100–1000 ppm) and anions of these ILs on the demulsification of produced emulsions were assessed using the bottle test technique at 75 °C. Viscosity and shear stress determination as well as interfacial tension (IFT) measurements were applied to affirm the effectiveness of these ILs to separate water/oil into phases. Bottle test results revealed that BMPT, BMPH, and BMPI demulsifiers removed water from the emulsion effectively, and the demulsification efficiency (% DE) increased with increasing dosage. BMPT, BMPH, and BMPI achieved the best % DE of 84%, 99%, and 59%, respectively, at 1000 ppm after 60 min. The highest water separation was recorded in PF6– anion because of its high hydrophobic nature. Viscosity and shear stress time-sweep measurements indicated the reduction in viscosities and shear stresses after injection of the demulsifiers. Also, the dynamic IFT results showed that these demulsifiers could mix with water–oil at the interface, break asphaltenes and resins molecules, and reduced the IFT from 16.01 to 12.47 mN/m. Optical microscopic emulsion images before and after demulsifier injection and the demulsification mechanism describing the water/oil separation stages are also discussed.