The mechanism of crude oil demulsifiers is based on phase inversion-reverse deformation theory. After adding the demulsifier, a phase inversion occurs, generating surfactants that produce the opposite emulsion type to that formed by the emulsifier (reverse demulsifier). These demulsifiers interact with hydrophobic emulsifiers to form complexes, thereby neutralizing the emulsifying properties. Another mechanism is interfacial film rupture through collision. Under heating or agitation, demulsifiers frequently collide with the interfacial film of the emulsion—either adsorbing onto it or displacing some surfactant molecules—which destabilizes the film, leading to flocculation, coalescence, and eventual demulsification.
Crude oil emulsions commonly occur during oil production and refining. Most of the world's crude oil is produced in an emulsified form. An emulsion consists of at least two immiscible liquids, where one is dispersed as extremely fine droplets (about 1 mm in diameter) suspended in the other.
Typically, one of these liquids is water, and the other is oil. The oil can be finely dispersed in water, forming an oil-in-water (O/W) emulsion, where water is the continuous phase and oil is the dispersed phase. Conversely, if oil is the continuous phase and water is dispersed, it forms a water-in-oil (W/O) emulsion. Most crude oil emulsions belong to the latter type.
In recent years, research on crude oil demulsification mechanisms has focused on detailed observations of droplet coalescence and the impact of demulsifiers on interfacial rheology. However, due to the complexity of demulsifier-emulsion interactions, despite extensive research, there is still no unified theory on the demulsification mechanism.
Several widely accepted mechanisms include:
1.Molecule displacement: Demulsifier molecules replace emulsifiers at the interface, destabilizing the emulsion.
2.Wrinkle deformation: Microscopic studies show W/O emulsions have double or multiple water layers separated by oil rings. Under heating, agitation, and demulsifier action, these layers interconnect, causing droplet coalescence.
Additionally, domestic research on O/W emulsion systems suggests that an ideal demulsifier must meet the following criteria: strong surface activity, good wettability, sufficient flocculation capability, and effective coalescence performance.
Demulsifiers can be classified based on surfactant types:
• Anionic demulsifiers: Include carboxylates, sulfonates, and polyoxyethylene fatty sulfates. They are less effective, require large dosages, and are sensitive to electrolytes.
• Cationic demulsifiers: Mainly quaternary ammonium salts, effective for light oil but unsuitable for heavy or aged oil.
• Nonionic demulsifiers: Include block polyethers initiated by amines or alcohols, alkylphenol resin block polyethers, phenol-amine resin block polyethers, silicone-based demulsifiers, ultra-high molecular weight demulsifiers, polyphosphates, modified block polyethers, and zwitterionic demulsifiers (e.g., imidazoline-based crude oil demulsifiers).
Post time: Aug-22-2025