Alcohol ethoxylates distillation

A typical prespotter formulation would contain petroleum distillates, linear alcohol ethoxylates, and/or nonyl phenol ethoxylates. Potential problems with using a harsh product are flammability, low volatility, clothing damage by way of color removal, and skin irritation. 

One of the modem technological trends consists in the production of ethoxylated alcohols having a rather narrow molecular weight distribution [9, 35-37]. It can be achieved by an intermediate distillation of the initial and low-ethoxylated products or by using more selective ethoxylation catalysts. Narrow-range ethoxylates present a new formulation potential, particularly in modem low-temperature detergents for automatic machines [38]. 

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. 

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, E. Kobus, Fractionation of ethoxylated fatty alcohols by molecular distillation, Tenside, Surfactants, Deterg., 1992,29, 345-348. 

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