methanolysisethanolysis

Methanolysis and ethanolysis are chemical processes in which methanol or ethanol acts as the nucleophile to cleave esters or to convert triglycerides into alkyl esters and glycerol. They are specific forms of transesterification in which the alcohol serves as the alkylating agent.

In biodiesel production, methanolysis, or methanol transesterification, converts fats and oils (triglycerides) into fatty acid methyl esters (FAME) and glycerol. The reaction is commonly catalyzed by base catalysts such as sodium or potassium hydroxide, though acid-catalyzed or enzymatic routes exist. Methanol is favored for its low cost and generally faster reaction rates, but its high miscibility with water and oils can promote soap formation when free fatty acids are present, requiring pretreatment or specialized catalysts.

Ethanolysis operates similarly but uses ethanol to yield fatty acid ethyl esters (FAEE) and glycerol. Ethanol derived from renewable sources can be advantageous for sustainability and regulatory reasons, but ethanolysis can be slower and may require different catalysts or reaction conditions to reach comparable conversions.

Catalysis for both processes can be homogeneous or heterogeneous. Enzymatic methods using lipases offer milder conditions but can be sensitive to high concentrations of alcohol and may require staged alcohol addition or immobilized enzymes. Process parameters such as alcohol-to-oil molar ratio, water content, and free fatty acid levels influence efficiency and soap formation, separation, and purification of the ester products.

Both methanolysis and ethanolysis are used to produce biofuels and specialty esters, with the choice guided by feedstock, economics, environmental considerations, and regional fuel standards.