Thursday, July 11, 2013

Ethoxylation & Ethoxylates

Ethoxylates are generally obtained by additions of ethylene oxide (EO) to compounds containing dissociated protons. The addition of EO to a substrate containing acidic hydrogen is catalyzed by bases or Lewis acids. Amphoteric catalysts, as well as heterogeneous catalysts are also used.

Substrates used for ethoxylation are primarily linear and branched C12-C18 alcohols, alkyl phenols, nonyl (propylene trimer) or decyl (propylene tetramer) groups, fatty acids and fatty acid derivatives.
The degree of ethoxylation ( the moles of EO added per mole of substrate ) varies over wide ranges, in general between 3 and 40, and is chosen according to the intended use.

Industrial ethoxylations are carried out mainly in a batchwise manner. The substrate together with the catalyst is first placed in the reaction vessel. The water introduced with the catalyst and the water formed in the first reaction is removed by heating or by passing N2 gas through the reaction mixture to avoid formation of polyglycols. The catalyst content is usually 0.1-1.0%. The ethoxylation is carried out between 130-180°C. The reactor contents must be cooled during the addition of EO. The reaction is carried out at 1-6 atm. The liquefied EO is dosed into the reaction.


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