What Is Monoethanolamine?
Monoethanolamine (MEA) is an organic compound containing one amino group (-NH2) and one hydroxy group (-OH) in its molecule.
It is known by various names such as colamine, ethylamine, 2-aminoethanol, 2-hydroxyethylamine, β-aminoethyl alcohol, and β-oxyethylamine.
Monoethanolamine is classified as a hazardous substance and a deleterious substance under various laws.
Uses of Monoethanolamine
Monoethanolamine finds wide application as an emulsifier due to its solubility in both water and oil. It is also utilized in synthetic detergents, metal corrosion inhibitors, cosmetics, pharmaceuticals, and agricultural chemicals. Additionally, it is employed in gas-cleaning processes for absorbing acidic gases from mixed gases.
1. Surfactant
Monoethanolamine acts as an emulsifier or surfactant, facilitating the uniform mixing of water and organic solvents due to its hydrophilic and lipophilic nature. Apart from serving as a surfactant raw material, it is employed as an emulsifier in cosmetics like soaps.
2. Absorbent
Monoethanolamine is commonly used for removing acidic gases from gas mixtures. For instance, aqueous solutions of monoethanolamine are applied to eliminate carbon dioxide from gases generated during metal heating processes.
Properties of Monoethanolamine
Monoethanolamine’s structural formula is HO-(CH2)2-NH2. At room temperature and pressure, it appears as a colorless liquid with a slight ammonia odor.
It exhibits properties of both alcohol and amine. With a molecular weight of 61.08, a density of 1.012 g/cm3, a melting point of 10.3°C, a boiling point of 170°C, and a flash point of 85°C, it reacts with acids to form esters, amides, and salts.
Other Information on Monoethanolamine
1. Other Ethanolamines
Monoethanolamine is one of the reaction products of ethylene oxide and ammonia, collectively known as ethanolamines, along with diethanolamine and triethanolamine. These ethanolamines can be partially separated by adjusting the ratio of ethylene oxide (the raw material) to ammonia. Their characteristics are as follows:
Diethanolamine
Containing a secondary amine (-NH-) and two hydroxy groups, its structural formula is (HO-CH2CH2)2NH, with a molecular weight of 105.14. It serves as an emulsifier in detergents, cosmetics, and waxes, and as a wetting agent in spinning.
Triethanolamine
Featuring a tertiary amine (-N=) and three hydroxy groups, its structural formula is (HO-CH2CH2)3N, with a molecular weight of 149.19.
It acts as an emulsifier, plasticizer, anti-corrosion additive, moisturizer, and base catalyst in condensation and organic synthesis reactions. It is also utilized as a nitrogen dioxide collector in the atmosphere and for analytical purposes.
2. Production of Monoethanolamine
Monoethanolamine is synthesized by reacting ethylene oxide with ammonia. However, depending on the reaction conditions, diethanolamine and triethanolamine may also form. Adjusting the ammonia-to-ethylene oxide ratio can minimize diethanolamine and triethanolamine formation while maximizing monoethanolamine yield.
The production process involves distilling the reaction mixture to separate monoethanolamine from diethanolamine and triethanolamine.
- Monoethanolamine Generation: CH2CH2O + NH3 → HO-CH2CH2-NH2
- Diethanolamine Generation: 2CH2CH2O + NH3 → (HO-CH2CH2)2NH
- Triethanolamine Formation: 3CH2CH2O + NH3 → (HO-CH2CH2)3N