Ethoxylation From Wikipedia, the free encyclopedia Jump to navigationJump to search This article is about the industrial scale process. For the attachment of polyethylene glycol to pharmaceuticals, see PEGylation. Ethoxylation is a chemical reaction in which ethylene oxide adds to a substrate. It is the most widely practiced alkoxylation, which involves the addition of epoxides to substrates.

In the usual application, alcohols and phenols are converted into R(OC2H4)nOH where n ranges from 1 to 10. Such compounds are called alcohol ethoxylates. Alcohol ethoxylates are often converted to related species called ethoxysulfates. Alcohol ethoxylates and ethoxysulfates are surfactants, used widely in cosmetic and other commercial products.[1] The process is of great industrial significance with more than 2,000,000 metric tons of various ethoxylates produced worldwide in 1994.[2]

Contents 1 Production 1.1 Alcohol ethoxylates 1.1.1 Ethoxylation/propoxylation 1.1.2 Ethoxysulfates 1.2 Other materials 2 Applications of ethoxylated products 2.1 Alcohol ethoxylates 2.2 Alcohol ethoxysulfates 3 Environmental and safety 3.1 Alcohol ethoxylates (AEs) 3.1.1 Human health 3.1.2 Aquatic and environmental aspects 3.2 Alcohol ethoxysulfates (AESs) 3.2.1 Biodegradation 3.2.2 In water 3.2.3 Human safety 4 References Production[edit] The process was developed at the Ludwigshafen laboratories of IG Farben by Conrad Sch?ller and Max Wittwer [de] during the 1930s.[3][4]

Alcohol ethoxylates[edit] Industrial ethoxylation is primarily performed upon fatty alcohols in order to generate fatty alcohol ethoxylates (FAE’s), which are a common form of nonionic surfactant (e.g. octaethylene glycol monododecyl ether). Such alcohols may be obtained by the hydrogenation of fatty acids from seed oils,[5] or by hydroformylation in the Shell higher olefin process.[6] The reaction proceeds by blowing ethylene oxide through the alcohol at 180 °C and under 1-2 bar of pressure, with potassium hydroxide (KOH) serving as a catalyst.[7] The process is highly exothermic (?H -92 kJ/mol of ethylene oxide reacted) and requires careful control to avoid a potentially disastrous thermal runaway.[7]

ROH + n C2H4O ? R(OC2H4)nOH The starting materials are usually primary alcohols as they tend to react 10–30× faster than do secondary alcohols.[8] Typically 5-10 units of ethylene oxide are added to each alcohol,[6] however ethoxylated alcohols can be more prone to ethoxylation than the starting alcohol, making the reaction difficult to control and leading to the formation of a product with varying repeat unit length (the value of n in the equation above). Better control can be afforded by the use of more sophisticated catalysts,[9] which can be used to generate narrow-range ethoxylates. Ethoxylated alcohols are considered to be a high production volume (HPV) chemical by the US EPA.[10]