ethoxylation

Ethoxylation is a chemical reaction in which ethylene oxide (EO) is added to substrates containing active hydrogen atoms, most commonly alcohols or phenols, to form poly(ethylene oxide) chains. The process yields ethoxylated derivatives that are typically nonionic surfactants, characterized by a hydrophobic tail attached to a hydrophilic polyether chain ending in a hydroxyl group. The average length of the ethylene oxide units, known as the EO number, determines the product’s polarity and properties.

In industrial practice, ethoxylation is carried out in the presence of a catalyst, often a basic substance such as sodium hydroxide or potassium hydroxide, at elevated temperatures and controlled pressure. The substrate is deprotonated to form a reactive alkoxide, which sequentially adds EO units in a chain-growth reaction. The process is carefully regulated to control the degree of ethoxylation and to minimize side reactions. Ethoxylation can be performed on fatty alcohols, especially fatty alcohols derived from plants or petrochemicals, as well as on phenols and other compounds.

Products and applications include alkyl poly(ethylene oxide) ethers (alkyl ethoxylates) and related nonionic surfactants used in detergents, cleaners, cosmetics, paints, textiles, agricultural formulations, and lubricants. The EO number and the structure of the hydrophobic moiety influence surfactant behavior, biodegradability, and compatibility with formulations. Safety considerations are important: ethylene oxide is toxic, flammable, and a respiratory irritant, requiring careful containment and process controls. Ethoxylation is distinct from propoxylation, and mixed ethoxylated/propoxylated products are common in complex formulations.