In 1897 Ludwig Knorr developed the modern industrial route (see below) and separated the products, including MEA, by fractional distillation, for the first time studying their properties.[13]
None of the ethanolamines were of any commercial importance until after the WWII industrial production of ethylene oxide took off.[12]
Occurrence in nature
MEA molecules are a component in the formation of cellular membranes and are thus a molecular building block for life. Ethanolamine is the second-most-abundant head group for phospholipids, substances found in biological membranes (particularly those of prokaryotes); e.g., phosphatidylethanolamine. It is also used in messenger molecules such as palmitoylethanolamide, which has an effect on CB1 receptors.[14]
MEA was thought to exist only on Earth and on certain asteroids, but in 2021 evidence was found that these molecules exist in interstellar space.[15]
Monoethanolamines can scrub combusted-coal, combusted-methane and combusted-biogas flue emissions of carbon dioxide (CO2) very efficiently. MEA carbon dioxide scrubbing is also used to regenerate the air on submarines.
MEA scrubbing solutions can be recycled through a regeneration unit. When heated, MEA, being a rather weak base, will release dissolved H2S or CO2 gas resulting in a pure MEA solution.[20][23]
Other uses
In pharmaceutical formulations, MEA is used primarily for buffering or preparation of emulsions. MEA can be used as pH regulator in cosmetics.[24]
It is an injectable sclerosant as a treatment option of symptomatic hemorrhoids. 2–5 ml of ethanolamine oleate can be injected into the mucosa just above the hemorrhoids to cause ulceration and mucosal fixation thus preventing hemorrhoids from descending out of the anal canal.
It is also an ingredient in cleaning fluid for automobile windshields.[25]
pH-control amine
Ethanolamine is often used for alkalinization of water in steam cycles of power plants, including nuclear power plants with pressurized water reactors. This alkalinization is performed to control corrosion of metal components. ETA (or sometimes a similar organic amine; e.g., morpholine) is selected because it does not accumulate in steam generators (boilers) and crevices due to its volatility, but rather distributes relatively uniformly throughout the entire steam cycle. In such application, ETA is a key ingredient of so-called "all-volatile treatment" of water (AVT).[citation needed]
Reactions
Upon reaction with carbon dioxide, 2 equivalents of ethanolamine react through the intermediacy of carbonic acid to form a carbamate salt,[26] which when heated usually reforms back to ethanolamine and carbon dioxide but occasionally can also cyclizate to 2-oxazolidone, generating amine gas treatment wastes.[27]
References
^ abNomenclature of Organic Chemistry : IUPAC Recommendations and Preferred Names 2013 (Blue Book). Cambridge: The Royal Society of Chemistry. 2014. pp. 649, 717. doi:10.1039/9781849733069-FP001. ISBN978-0-85404-182-4. For example, the name 'ethanolamine', which is still widely used, is badly constructed because of the presence of two suffixes; it is not an alternative to the preferred IUPAC name, '2-aminoethan-1-ol'.
^Reitmeier, R.E.; Sivertz, V.; Tartar, H.V. (1940). "Some Properties of Monoethanolamine and its Aqueous Solutions". Journal of the American Chemical Society. 62 (8): 1943–44. doi:10.1021/ja01865a009.
^Carrasco, F. (2009). "Ingredientes Cosméticos". Diccionario de Ingredientes Cosméticos 4ª Ed. www.imagenpersonal.net. p. 306. ISBN978-84-613-4979-1.
^Federal Motor Vehicle Safety Standards. U.S. Department of Transportation, National Highway Traffic Safety Administration. 1994. p. Part 571; S 108—PRE 128.
