Production process of fatty alcohol ethoxylates (AEO)

The production process of fatty alcohol ethoxylates (AEOs) is mainly based on the addition reaction of ethylene oxide to fatty alcohols, a process called “polyetherification” or “ethylene oxide addition reaction”. Fatty alcohol ethoxylates (AEOs) are nonionic surfactants that are widely used in detergents, emulsifiers, and dispersants. The following is a detailed introduction to the production process of fatty alcohol ethoxylate.

First, raw material selection and preparation

The main raw materials for the preparation of fatty alcohol ethoxylates (AEO) include fatty alcohols and ethylene oxide. Choosing the right type of fatty alcohol, molecular weight and purity, as well as the amount of ethylene oxide to do, has a direct impact on the properties and performance of the final product.

1. Fatty alcohols
   Commonly used fatty alcohols are C10-C18 linear saturated fatty alcohols, depending on the performance requirements of the target product.

• Medium carbon chain fatty alcohols: such as lauryl alcohol and myristic alcohol in C12-C14, the prepared AEO is suitable for use in detergents and detergents.
• Long-chain fatty alcohols: palmityl alcohol and stearyl alcohol, such as C16-C18, are used to prepare highly effective emulsifiers and solubilizers.

1. Ethylene Oxide
   Ethylene oxide is a highly toxic and flammable chemical that needs to be strictly controlled when operating. The amount of ethylene oxide determines the degree of polymerization and hydrophilic properties of AEO.
2. Catalyst
   Commonly used catalysts include basic catalysts such as sodium hydroxide, potassium hydroxide, and barium hydroxide, which can promote the ring-opening polymerization of ethylene oxide and improve the conversion of the product.

Second, reaction equipment

In the production process of fatty alcohol ethoxylate, a reaction kettle is commonly used for polymerization reaction. The reactor is generally a high-pressure stainless steel vessel, which has the characteristics of high temperature and high pressure resistance, and is equipped with a stirring system and a temperature and pressure monitoring system to ensure the uniformity and safety of the reaction.

1. Reactor
   It should have the functions of heating, cooling, feeding and discharging to ensure the controllability of the reaction process. The kettle is equipped with a high-efficiency stirring device to avoid uneven polymerization reaction.
2. Condensing device
   Due to the strong volatility of ethylene oxide, the reactor is equipped with a condensing device to cool and recover the unreacted ethylene oxide to improve the reaction efficiency.
3. Exhaust gas treatment system
   Ethylene oxide and the gas off-gases of the product must be treated to avoid environmental contamination and to protect operator safety.

Third, the production process steps

The production process of fatty alcohol ethoxylates (AEO) is mainly divided into the following steps: fatty alcohol preparation, catalyst addition, addition reaction, post-treatment and finished product testing.

1. Raw material preparation

The fatty alcohols are refined to an anhydrous state, and their moisture and acid number are tested to ensure that they meet the reaction requirements. Too much moisture content can affect the efficiency of the reaction and the quality of the product.

2. Add catalyst

The refined fatty alcohol was transferred to the reaction kettle, and an appropriate amount of catalyst was added. The catalyst is usually based on alkaline substances, which can promote the addition reaction of ethylene oxide to fatty alcohols. The amount of catalyst needs to be strictly controlled, too much may cause side reactions and affect product quality.

3. Ethylene oxide addition reaction

Ethylene oxide addition reaction is the core step in the preparation of fatty alcohol ethoxylate, which is divided into the following stages:

• Heating and dehydration: Fatty alcohols are heated to 80-100 °C under the action of a catalyst, and a certain vacuum condition is maintained to remove residual water and reduce the occurrence of side reactions.
• Add ethylene oxide: After the reactor reaches a suitable temperature, slowly add ethylene oxide. Under the action of an alkaline catalyst, ethylene oxide undergoes a nucleophilic addition reaction with fatty alcohols. Each molecule of ethylene oxide produces an oxyvinyl group (-CH2CH2O-) structure on the fatty alcohol molecule.
• Control reaction temperature and pressure: The reaction process will produce a certain amount of exothermy, so the temperature should be kept between 120-150°C, too high will cause side reactions. The reaction pressure is generally maintained at 0.2-0.5 MPa, and the reaction time is usually 4-8 hours.
• Reaction Stop: When the addition reaction reaches a predetermined degree of polymerization, the reaction is stopped by cooling and the unreacted ethylene oxide is removed by nitrogen purging.

4. Neutralization and post-processing

After the polymerization reaction is completed, neutralization and post-processing are required:

• Catalyst Neutralization: Use an acidic substance such as acetic acid or phosphoric acid to neutralize the residual alkaline catalyst to avoid over-alkaline products.
• Impurity removal filtration: The reaction solution is filtered out of impurities and insoluble substances, so that the product is pure and transparent, and the appearance quality of the product is improved.
• Desolvation and refining: If necessary, solvents and small amounts of oligomers are removed by vacuum distillation or other refining methods to obtain high-purity fatty alcohol ethoxylates.

Fourth, product testing and quality control

The aliphatic alcohol ethoxylates produced are tested and quality controlled to ensure they meet industry standards and usage requirements.

1. Detection Indicators

• Hydroxyl value: reflects the degree of polymerization of fatty alcohols, which is related to the hydrophilic properties of AEO.
• Acid number: Residual acidic components will affect the stability and effectiveness of the product.
• pH: It should be neutral or weakly alkaline, too strong acidity and alkalinity is not conducive to use.
• Molecular weight distribution: The higher the molecular weight uniformity, the more stable the AEO performance.

1. Performance Test

• Surface Tension: Reflects the surface activity of AEO, and its decontamination ability can be judged by measuring the surface tension.
• Emulsifying Properties: This is especially critical in emulsifier applications, and testing emulsifying performance can predict how AEO will behave in emulsified and dispersed systems.
• Solubility: The solubility of fatty alcohol ethoxylates in water and other solvents directly affects their use in detergents and emulsifiers.

5. Environmental protection and safety measures for fatty alcohol ethoxylates

Attention should be paid to safety and environmental protection in the production process of fatty alcohol ethoxylate:

1. Wastewater Treatment
   The wastewater generated in the production process contains unreacted raw materials, catalyst residues and by-products, etc., which need to be treated through neutralization, oxidation and other processes to meet environmental protection discharge standards.
2. Exhaust gas treatment
   Ethylene oxide is highly toxic and may contain trace amounts of ethylene oxide and other volatile organic compounds (VOCs) in the exhaust gas. Exhaust gas is treated by methods such as activated carbon adsorption or catalytic combustion to reduce pollution.
3. Production Safety
   Ethylene oxide is flammable and toxic, and needs to be reacted in a tightly sealed and ventilated environment to prevent gas leakage and electrostatic ignition.

Sixth, the main application of fatty alcohol ethoxylate

1. Detergent
   The AEO series is widely used in household cleaners and industrial cleaners due to its excellent decontamination and foaming properties.
2. Emulsifier
   AEO has excellent performance in emulsification and solubilization, and is commonly used in emulsification systems in the cosmetics, food and pharmaceutical industries.
3. Textile auxiliaries
   In the textile industry, fatty alcohol ethoxylates can be used as lubricants, softeners, etc., to increase the softness and comfort of fabrics.
4. Other Areas
   AEO can also be used as oilfield chemicals, leather treatment agents, etc.