The Nemesis of Emulsion Stability – Demulsifiers|Resources|UNPChemicals

October 31, 2025

The Nemesis of Emulsion Stability – Demulsifiers

In industrial production, the stability and effective separation of emulsions are crucial technical challenges. An emulsion is a mixture formed by two or more immiscible liquids, such as a mixture of oil and water. These mixtures can form stable emulsions under specific conditions, but in many application scenarios, we need to separate the different phases in these emulsions. At this time, the role of demulsifiers becomes particularly important. This article will briefly introduce the principle, types, application in the oilfield industry and selection principles of demulsifiers, aiming to provide some help for professionals in related fields.

What is Demulsifier？

Demulsifier is a special type of surfactant whose main function is to destroy the stability of emulsions, enabling the separation of different phases that were originally mixed together. In an emulsion, the emulsifier reduces the tension at the oil-water interface, allowing two immiscible liquids to form a stable mixture. Demulsifiers, however, replace the emulsifier's adsorption at the interface, increasing the interfacial tension, thereby destabilizing the emulsion and achieving separation.

Demulsifiers are polymerized from fatty alcohols, propylene oxide, and ethylene oxide. They are easily soluble in water, appearing as pale yellow or milky white viscous liquids with a soapy odor. Their freezing point ranges between 25 and 40 degrees Celsius, the hydroxyl value does not exceed 60 mg potassium hydroxide per gram, and the aqueous solution is milky white.

When using demulsifiers, it is necessary to first adjust the pH value of the emulsion. For strongly alkaline and strongly acidic emulsions, the pH value generally needs to be adjusted to the range of 1 to 10. In the treatment of oily emulsion wastewater in industries such as petroleum, chemical engineering, wool spinning, and mechanical processing, in addition to physical demulsification methods (such as heating, membrane separation, and electric field demulsification), demulsifiers are also commonly used for chemical treatment.

Commonly used demulsifiers are highly dispersible mixtures composed of multiple components. For the demulsification of oil-in-water emulsions, inorganic substances with cations such as H+, Al3+, and Fe3+ are usually used as demulsifiers, such as inorganic acids and ferric sulfate. For the demulsification of water-in-oil emulsions, anionic and non-ionic surfactants or their mixtures are generally used as demulsifiers.

Demulsification Mechanism

Surface activity: Demulsifiers have higher activity than emulsifiers and can quickly act on the oil-water interface, replacing or neutralizing the emulsifier, reducing interfacial tension, destabilizing water-in-oil emulsions, and promoting oil-water separation. However, the level of activity is not always proportional to demulsification ability.
Reverse emulsification: Hydrophilic demulsifiers can convert water-in-oil emulsions into oil-in-water emulsions. By utilizing the conversion of the emulsification process and the instability of oil-in-water emulsions, oil-water separation is achieved, and the aqueous phase aggregates into large water droplets and settles.
Wetting and penetration: Demulsifiers can dissolve the natural emulsifier at the oil-water interface, eliminating its hindrance to water droplet coalescence. For hydrophilic solid particles, demulsifiers pull them into water droplets; for lipophilic substances, they make them leave the interface and enter the oil, facilitating the merging and settling of water droplets.
Counterion action: For negatively charged water droplets, ionic demulsifiers weaken electrostatic repulsion by neutralizing positive charges, destroying the interfacial film, and promoting the merging and settling of water droplets.

Although the demulsification mechanism of demulsifiers is not yet perfect, two conclusions have been summarized from long-term practice: ① The molecular weight of the demulsifier must be greater than that of the natural emulsifier to achieve effective demulsification; ② If the demulsifier is used as an emulsifier for oil-water mixtures, it will form a reverse emulsion, namely an oil-in-water emulsion.

Types and Characteristics

According to their chemical properties and application fields, demulsifiers can be divided into the following categories:

Anionic demulsifiers: These demulsifiers form negatively charged ion groups in water and are often used for the demulsification of oil-in-water emulsions. They are usually composed of carboxylates, sulfonates, and polyoxyethylene fatty sulfate salts. Anionic demulsifiers have strong detergency and dispersibility but are easily affected by electrolytes in water.
Cationic demulsifiers: These demulsifiers form positively charged particle groups in water and are mainly used for the demulsification of water-in-oil emulsions. The representative of cationic demulsifiers is quaternary ammonium salt compounds, which have obvious effects on general crude oil but are not suitable for heavy oil and aged oil.
Non-ionic demulsifiers: These demulsifiers do not produce ions in water and are therefore not affected by electrolytes. They are usually composed of block polyethers, alkylphenol formaldehyde resin block polyethers, etc., and are suitable for the demulsification of various types of emulsions. Non-ionic demulsifiers have good wettability and permeability and are suitable for systems with low temperature and high electrolyte content.
UNPChemicals’ DEMET® series stands out as a portfolio of high-performance non-ionic demulsifiers, engineered to tackle emulsion separation challenges across industrial scenarios, with a strong focus on oilfield applications. This series encompasses multiple product types, including Alkoxylated resins, Diepoxides, Polyoxyalkylene glycols, and Polyacrylates. Leveraging their non-ionic nature, these demulsifiers exhibit excellent adaptability to various emulsion systems, resisting interference from electrolytes while delivering robust demulsification efficiency. Whether in crude oil dehydration, oil-water separation during refining, or other oilfield processes, the DEMET® series effectively disrupts emulsion stability, promotes rapid phase separation, and ensures smooth operations while enhancing overall productivity.
Amphoteric ionic demulsifiers: These demulsifiers can exhibit cationic or anionic characteristics in solutions with different pH values, so they can effectively demulsify under both acidic and alkaline conditions. They are cationic in acidic solutions and anionic in alkaline solutions, with good adaptability.

Application in the Oilfield Industry

In the oilfield industry, demulsifiers have a wide range of applications, especially in oilfield production and oil refining processes. Crude oil emulsions need to undergo demulsification treatment to separate oil and water, ensuring the quality of crude oil. Demulsifiers can effectively reduce the viscosity of crude oil, prevent oil well blockage, and improve the production efficiency of oil wells. During the extraction process, crude oil is often mixed with water to form emulsions, which increases the difficulty of transportation and processing. After adding demulsifiers, the stability of the emulsion is destroyed, oil and water are separated, which not only facilitates the transportation of crude oil but also reduces the corrosion of equipment by water, extending the service life of the equipment. In the oil refining process, the separation of oil and water is also a key link. Demulsifiers can improve the efficiency of oil-water separation, ensure the smooth progress of the refining process, and improve the quality of refined oil products.

Selection Principles

When selecting a demulsifier, the following principles need to be considered:

Surface activity: The demulsifier must have sufficient surface activity to effectively replace the emulsifier and destroy the stability of the emulsion. When selecting, the HLB value (hydrophilic-lipophilic balance value) of the demulsifier should be considered to ensure its effectiveness in a specific system.
Stability of the interfacial film: The interfacial film formed by the demulsifier at the oil-water interface should be easy to break, so that the droplets can coalesce. When selecting, the molecular structure and hydrophilic-lipophilic balance of the demulsifier should be considered to ensure that it can effectively destroy the interfacial film of the emulsion.
Charge neutralization: For charged emulsifiers, a demulsifier with the opposite charge should be selected to neutralize the charge on the droplet surface. This is particularly important for water-in-oil emulsions, as the stability of such emulsions largely depends on the charge on the droplet surface.
Molecular weight: Demulsifiers with relatively large molecular weights are more conducive to the aggregation and separation of droplets. High molecular weight demulsifiers can aggregate droplets through bridging, thereby coalescing, stratifying, and demulsifying.
Specific applications: For specific emulsion systems, it may be necessary to select specific demulsifiers to achieve the best demulsification effect. For example, for emulsions containing high concentrations of solid particles, demulsifiers with good wettability may need to be selected.

Conclusion

As a critical industrial chemical, demulsifiers play an indispensable role in the separation and treatment of emulsions, especially in the oilfield industry where efficient oil-water separation directly impacts production efficiency and product quality. Gaining a thorough understanding of demulsifiers’ working principles, types, oilfield applications, and selection criteria is pivotal to optimizing industrial processes and enhancing operational performance. With the advancement of science and technology and the evolving industrial demands, the research and application of demulsifiers will continue to deepen— and UNPChemicals’ DEMET® series non-ionic demulsifiers stand at the forefront of this development. Comprising Alkoxylated resins, Diepoxides, Polyoxyalkylene glycols, and Polyacrylates, the DEMET® series delivers exceptional adaptability and demulsification efficiency, effectively addressing emulsion challenges in oilfield production and refining. By integrating the DEMET® series into industrial workflows, enterprises can achieve more stable, efficient phase separation, driving productivity improvements and unlocking greater operational value. Moving forward, UNPChemicals will remain committed to advancing demulsifier technology, bringing reliable and high-performance solutions to support the sustainable development of industrial production.