What Is Monoethanolamine? Properties, Uses and Industrial Applications
Meta description: Monoethanolamine (MEA, CAS 141-43-5) is a primary alkanolamine used in gas treating, detergents and CO₂ capture. A practical technical overview for engineers and buyers.
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If you have ever worked on a natural-gas sweetening unit, a CO₂-capture pilot plant, a detergent formulation or a metalworking fluid, you have encountered monoethanolamine. It is one of those "invisible" industrial chemicals — not a household name, but almost every industrial process touches it somewhere.
What Is Monoethanolamine?
Monoethanolamine (MEA), also called 2-aminoethanol or simply ethanolamine, is the simplest alkanolamine. Its formula is HO–CH₂CH₂–NH₂. Molecules like this are interesting because they are both an amine (basic, can absorb acids) and an alcohol (hydrophilic, can form esters). That dual nature is why MEA is such a versatile industrial chemical.
At room temperature, MEA is a colourless, viscous liquid with a faint ammonia-like odour. It is fully miscible with water, ethanol and acetone, and immiscible with non-polar solvents like benzene.
Key Properties
| Property | Value |
|---|---|
| CAS number | 141-43-5 |
| Molecular formula | C₂H₇NO |
| Molecular weight | 61.08 g/mol |
| Boiling point | 170 °C |
| Freezing point | 10.3 °C |
| Density (20 °C) | 1.012 g/cm³ |
| pKa (25 °C) | ~ 9.5 |
| Flash point (closed cup) | ~ 93 °C |
| Vapour pressure (20 °C) | ~ 67 Pa |
MEA freezes at just above room temperature — around 10 °C — so in cold climates drums can solidify over winter. This is a practical handling detail engineers often underestimate.
How Is MEA Made?
MEA is produced by reacting ethylene oxide with aqueous ammonia. At a high ammonia-to-ethylene-oxide ratio, the reaction favours the mono-addition product (MEA). Lower ammonia ratios give mixtures of MEA, diethanolamine (DEA) and triethanolamine (TEA), which are then separated by vacuum distillation.
Global MEA capacity is concentrated in China, the United States, Western Europe and the Middle East. Chinese plants in Jiangsu, Shandong and Liaoning account for a large share of seaborne trade.
Where Is MEA Used?
1. Acid-Gas Treating and CO₂ Capture (~ 40% of demand)
MEA is the benchmark solvent for removing CO₂ and H₂S from natural gas, refinery off-gas and — increasingly — power-plant flue gas. In a typical amine unit, 15–20 wt% MEA solution is circulated through an absorber tower, picks up acid gas, then flows to a stripper where heat releases the CO₂ for compression or venting.
2. Detergents and Cleaning Products (~ 20%)
MEA neutralizes fatty acids to form "ethanolamine soaps." These are used in heavy-duty laundry detergents, car washes and industrial cleaners because they combine good grease-cutting with low corrosivity to aluminium.
3. Metalworking and Corrosion Inhibition (~ 10%)
In cutting fluids, grinding fluids and cooling systems, MEA acts as a pH buffer and corrosion inhibitor. It neutralizes organic acids generated during machining and protects ferrous surfaces.
4. Textile Chemicals (~ 10%)
MEA is a building block for dye-leveling agents, wool-scouring compounds and softeners. It also finds use as a Scroop agent for fabrics.
5. Personal Care and Pharmaceuticals (~ 10%)
MEA is a pH adjuster in cosmetics and a building block for certain drug salts.
6. Other Uses (~ 10%)
Agricultural intermediates, photographic chemicals, rubber additives and gas scrubbing in welding fume extraction.
Safety at a Glance
MEA is corrosive to skin and eyes. It is classified UN 2491 for sea transport (corrosive liquid). Inhalation of vapours can irritate the respiratory tract. Standard PPE — chemical goggles, butyl-rubber gloves, apron — is required for handling bulk MEA. Full details are in the SDS.
Why MEA Still Matters
Despite 80 years of commercial use and the rise of formulated amine blends (MDEA + piperazine activators, sterically hindered amines), MEA remains the reference solvent for deep CO₂ removal. Its low cost, well-understood chemistry and high reactivity make it the default when engineers design a new treating unit — and the benchmark against which newer solvents are measured.
*About the author: The author works with industrial alkanolamines and writes on chemical engineering topics for buyers and process engineers. COAs and technical data sheets for MEA are available through ChinaAmines.
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