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.