Overview of Epoxidized Linseed Oil Production Process

Epoxidized Linseed Oil (ELO) is a bio-based plasticizer and heat stabilizer obtained by selectively epoxidizing linseed oil. It is widely used in PVC, coatings, and rubber formulations. The process aims to achieve a high epoxy value, low by-product formation, and stable color, while also ensuring safe and green production.

Principles and Raw Materials

• Reaction Mechanism: Prilezhaev epoxidation of carbon-carbon double bonds using peroxy acids, commonly generated in situ using peracetic acid or performic acid systems (formed by the reaction of hydrogen peroxide with acetic acid/formic acid under acid catalysis).
• Catalytic System: Solid acids such as acidic ion exchange resins or heteropolyacids are preferred to reduce corrosion and post-treatment burdens.
• Base Oil Requirements: Low moisture, low phosphorus content, high and stable iodine value. The higher the degree of unsaturation, the higher the potential epoxy value.

Process Flow

1. Pretreatment: Degumming, drying, and fine filtration to control moisture and impurities, reducing the risk of side reactions.
2. Epoxidation Reaction: Hydrogen peroxide is added stepwise under stirring at 50–65 ℃ to generate peroxy acids in situ. Heat release and pH are controlled to suppress epoxy ring opening. Typical molar ratios are C═C: H2O2≈1:1.1–1.3, Acid: H2O2≈0.2–0.5.
3. Post-treatment: Washing with water to neutralize to near neutrality, vacuum dehydration. If necessary, decolorization and deodorization with activated clay, followed by fine filtration to obtain the finished product. By-product acid phase and washing water can be recycled and treated.

Key Control Points

• Temperature and Heat Transfer: Epoxidation is strongly exothermic, requiring batch-wise addition of reactants, enhanced stirring, and efficient heat exchange to prevent hot spots that can trigger ring opening and color increase.
• Medium and Impurities: Control of free acids and metal ions to avoid strong acidity or excessive moisture that can cause epoxy ring opening and polymerization.
• Process Monitoring: Real-time tracking of iodine value decrease and epoxy value increase, adjusting feed rate and stirring intensity as needed.
• Safety: Standardized storage and metering of peroxides, use of corrosion-resistant materials, and provision of pressure relief and interlock protection.

Quality Indicators and Testing

• Key Indicators: Epoxy value (OOC) approximately 8.5–9.0%, residual iodine value <6 g I2/100 g, acid value <1.0 mgKOH/g, stable color and viscosity.
• Testing Methods: HBr-acetic acid method for epoxy value, acid-base titration for acid value, FTIR monitoring of the epoxy band (approximately 823 cm⁻¹) and double bond decay, and thermal stability and volatile content tests as needed.

Greening and Applications

• Green Enhancement: Solid acid catalysis, closed-loop water washing, waste heat recovery, and continuous processing (such as microreactors) all help reduce energy consumption and waste emissions.
• Applications and Storage: In PVC, it functions as both a plasticizer and an HCl scavenger, and can be used for epoxy resin modification and anti-migration formulations. The finished product should be stored in a closed container, protected from light and moisture, and away from acids, water, and metal salts to prevent degradation.

In summary, the key process points of epoxidized linseed oil are the controlled in-situ generation of peroxy acids, precise heat and material management, and a clean post-treatment system, thereby achieving high epoxy value, low by-product formation, and sustainable industrial manufacturing.