Demulsifier

Introduction

Demulsifier, also known as emulsion breaker, is a class of specialty chemical used to promote separation of oil and water. Demulsifier is mainly used in crude oil exploitation. Crude oil is produced from underground in the form of oil-water emulsion. If not timely dehydration, it will increase the pump, pipe line and storage tank load and cause metal surface corrosion and scaling. The crude oil in the discharge water will also cause environmental pollution and waste of resources. Therefore, it is necessary to demulsify and dehydrate crude oil from both economic and environmental perspectives. In addition, with the development of sewage treatment needs, many seriously emulsified oil-bearing industrial wastewaters also need demulsification purification treatment. At present, adding demulsifier is the most common demulsification method because of the advantages of high activity and quick effect.

Fig. 1. Demulsification phenomenon after adding demulsifier.

Development

The development of demulsifier can be divided into the following stages.

• From 1920 to 1930's, the first generation of demulsifier is mainly low molecular weight anionic surfactant, such as naphthenate, fatty acid salt, etc.
• In 1940s, the industrial production of ethylene oxide led to a leap in demulsifier research and application, and the emergence of polyoxyethylene ether non-ionic surfactants. The most representative demulsifiers are surfactants with structures of ethylene oxide and propylene oxide, which are still the main source of demulsifier, today.
• After 1960's, the third generation of demulsifier represented by polymer polyether demulsifier developed rapidly, include SP, AE and AP demulsifiers.
• After 1980's, polyurethane, amphoteric ionic and polymer demulsifier have been developed continuously.
• Since the late 1980s, based on the improvement of the third generation of polyether demulsifier, a large number of new demulsifiers have been researched and developed. The representative products are acrylic tetrad copolymerization demulsifier, organic polyamine demulsifier, cationic amide demulsifier, Gemini surfactant and hydrophobic association trimer.

Fig. 2. The typical structures of (a) acrylic tetrad copolymerization demulsifier, (b) organic polyamine demulsifier, (c) cationic amide demulsifier and (d) hydrophobic association trimer.

Mechanism

In recent years, a lot of research works have been carried out on the action mechanism of demulsifier. But, due to the complex of demulsifier function, no unified theory has been formed up to now. At present, the recognized demulsification mechanisms are as follows.

• Phase transition mechanism: With the addition of demulsifier, a phase transformation occurs. In this theory, demulsifier is easy to form complex with the emulsifier so that the emulsifier loses its emulsification, achieving the effect of demulsification.
• Collision breaking interface membrane mechanism: Under the condition of heating or stirring, the demulsifier has more chances to collide with the interface film of emulsion, or adsorbs on the interface film of emulsion, or displaces part of the surface-active substances of emulsion, so as to break the interface film and greatly reduce its stability. Thus, the phenomenon of flocculation, coalescence and demulsification occur.
• Solubilization mechanism: The demulsifier can form micelles by a molecule or a few molecules. The micelles can solubilize emulsifier molecules, causing emulsified oil demulsification.
• Colloidal mechanism: The mechanism holds that the demulsifier molecules have colloidal action at the oil-water interface, that is, hydrophobic film forming substances (such as colloid) and macromolecular wax crystals are converted into substances that can be dissolved in the oil phase. Then the substances disperse in the oil in colloidal form, thus promoting the coalescence between droplets and greatly increasing the interfacial tension.

Alfa Chemistry can offer you with various demulsifiers. If you can't find the desired product in our product catalog, we also offer you with custom synthesis service. Please contact us, if you have any needs.