What Ethanolamine Is
Ethanolamine (CAS 141-43-5), also called monoethanolamine or MEA, has the formula C2H7NO and a molecular weight of about 61.08. It is a colourless, viscous liquid with a boiling point near 170 degrees Celsius, an ammoniacal odour and complete miscibility with water. Its industrial value comes from having two functional groups on a very small molecule: a primary amine that reacts readily with acids and with acidic gases, and a hydroxyl group that keeps the molecule water soluble and compatible with many formulations.
MEA is the first member of the ethanolamine family, which also includes diethanolamine (CAS 111-42-2) and triethanolamine (CAS 102-71-6). The three are produced together and separated by distillation, and they are sold separately for different duties.
Gas Treating: Carbon Dioxide and Hydrogen Sulfide Removal
The largest industrial outlet is gas sweetening. Aqueous MEA solutions, typically in the 15 to 30 percent by weight range, are circulated through an absorber where the solution contacts natural gas, refinery gas, synthesis gas or biogas and chemically absorbs acidic gases, chiefly carbon dioxide and hydrogen sulfide. The rich solution is then regenerated in a stripper at elevated temperature, where the acid gases are released and the lean amine is returned to the absorber.
This chemistry works because MEA is a fast-reacting primary amine, which gives high absorption efficiency in compact equipment. The operating costs to watch are thermal energy for regeneration, solution losses through evaporation and entrainment, and the gradual formation of heat-stable salts when the amine reacts with stronger acids in the gas stream. Those salts reduce the effective amine concentration and must be controlled by reclaiming or by adding fresh material. Corrosion of carbon steel in the rich solution side of the loop is the other classic problem, and it is managed by concentration control, filtration, and the use of corrosion-resistant materials at hot points.
Surfactants, Detergents and Personal Care
MEA is a building block for surfactants and emulsifiers. Reacted with fatty acids it forms amine soaps that appear in liquid detergents, hard-surface cleaners, industrial degreasers, polishes and metalworking fluids, where they combine detergency with emulsifying power. It is also used to neutralise acidic components in formulations and to raise pH.
In personal care products, ethanolamines act as pH adjusters, emulsifiers and neutralisers in shampoos, conditioners, creams and lotions, and they help disperse oils and pigments. Cosmetic grades are controlled for nitrosamine precursors and are supplied with tight limits on secondary amine content, because the regulatory expectation in this sector is that nitrosamine formation is prevented rather than managed.
Agrochemicals, Textiles, Cement and Metalworking
| Industry | Function of ethanolamine |
|---|---|
| Agrochemicals | Neutralises acidic active ingredients to form water-soluble amine salts for liquid formulations |
| Textiles | Dyeing auxiliary, softening agent and pH control in finishing liquors |
| Cement | Grinding aid that reduces mill energy consumption and improves powder flow |
| Metalworking | Amine soap component in cutting fluids, with corrosion inhibition and emulsification |
| Wood and coatings | Neutralising agent in waterborne resin and coating systems |
Quality Parameters, Handling and Storage
Purchase specifications for MEA usually control assay, water, colour and the ratio of secondary and tertiary amines. Water is determined by Karl Fischer titration following ASTM E203 practice, and colour is measured on the platinum-cobalt scale used in ASTM D1209. Colour is a sensitive indicator of contamination, because MEA is hygroscopic and reacts with carbon dioxide in air to form carbamate salts, which darken the product and consume active amine.
Tanks should be blanketed with dry nitrogen and kept closed to limit moisture and carbon dioxide pickup. MEA freezes near 10 degrees Celsius, so heat tracing or heated storage is needed in cold climates. Because amines attack copper, zinc and galvanised surfaces, storage and transfer equipment is normally carbon steel, stainless steel or compatible plastic. MEA is alkaline and corrosive to skin and eyes, and it is classified as a hazardous material for transport under UN 2491, so handling requires chemical splash goggles, face protection and suitable gloves, with immediate washing after any contact.
Frequently Asked Questions
Q: What is ethanolamine used for?
A: The largest use is gas treating, where aqueous monoethanolamine removes carbon dioxide and hydrogen sulfide from natural gas, refinery gas and synthesis gas. Other significant uses are surfactant and detergent production, agrochemical salts, textile auxiliaries, metalworking fluids and cement grinding aids.
Q: What is the difference between MEA, DEA and TEA?
A: They are the mono, di and tri ethanolamines, sharing a common production route and separated by distillation. MEA is the most reactive and the most used in gas treating; DEA and TEA are used where lower volatility or a different balance of amine and hydroxyl groups is needed.
Q: Why must ethanolamine be stored under nitrogen?
A: It absorbs both moisture and carbon dioxide from air, forming carbamate salts that consume active amine and raise colour. A dry nitrogen blanket keeps the assay and colour within specification.
Q: Why does ethanolamine need heated storage in cold weather?
A: It freezes close to 10 degrees Celsius, so tanks and lines require trace heating or lagging to stay pumpable in winter conditions.
Q: What materials are suitable for ethanolamine service?
A: Carbon steel, stainless steel and compatible plastics. Copper, zinc, aluminium and galvanised surfaces are attacked by amines and should be avoided in tanks, lines, pumps and instrument parts.
