Acid ethoxylates distillation

When the apparatus is in use, the bulb of the flask containing the hydriodic aid and the substance is heated in an oil bath at 130°. The methyl iodide is carried over into the absorber by a slow current of dry carbon dioxide, passing in at the side tube. The temperature on the thermometer should not be higher than 35°—40° for methoxyl, and 40° for ethoxyl compounds. At these temperatures no hydriodic acid is distilled over. As a further precaution, the neck of the flask is slanted away from the source of heat. 

For methoxyl and ethoxyl group estimations (p. 479) hydriodic acid (B.P. 127°) is distilled over phosphorus in a current of carbon dioxide. 

The industrial process [23, 212, 213] of ethoxylation and propoxylation is usually a semi-batch process. The starter alcohol and KOH are mixed and water is removed by distillation. In a second step, monomers are fed into the reactor, where the feed rate is chosen so as to be able to remove the heat of polymerization and to keep the latent heat of polymerization of unreacted monomers in a safe state. By this process, homopolymers and random copolymers are accessible. Block copolymers are produced by successive feeds of the respective monomers. Catalyst is removed by addition of acids and subsequent crystallization and filtration of precipitated salts. An optional fourth step is the removal of volatile compounds by distillation. 

These can be considered to be esters of fatty acids and polyethylene glycol, although they are generally made by direct addition of EO to the acid. They contain, besides the main monoester ingredient, diester, free acid, and free PEG. This class includes tall oil ethoxylates. Tall oil fatty acids are linear, long-chain, and unsaturated, being obtained by distillation of tall oil, a water-insoluble, ether-soluble fraction of pulp mill waste (3). 

Molecular distillation of an ethoxylated C12/C14 alcohol reaction mixture was possible up to about the 4-mole ethoxylate, but each fraction contained a mixture of diiferent alkyl chain lengths and varying degree of ethoxylation, as well as also containing PEG (6). Similar results were obtained for fatty acid esters of decanol, glycerol, and sorbitan (5). Thus, distillation is only suitable for preliminary sample workup, not for isolation of pure compounds. 

Szelag, H., W. Zwierzykowski, Fractionation of ethoxylated fatty acids using molecular distillation, Tenside, Surfactants, Deterg., 1984,21,14-16. 

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