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

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.