| HS Code | |
| Name | Monoethanolamine (MEA) |
| Iupacname | 2-Aminoethanol |
| Chemicalformula | C2H7NO |
| Molecularweight | 61.08 g/mol |
| Casnumber | 141-43-5 |
| Appearance | Colorless viscous liquid |
| Odor | Ammonia-like |
| Meltingpoint | 10.3 °C |
| Boilingpoint | 170.0 °C |
| Density | 1.0117 g/cm3 at 20 °C |
| Vaporpressure | 0.2 mmHg at 20 °C |
| Flashpoint | 93 °C (closed cup) |
| Autoignitiontemperature | 410 °C |
| Viscosity | 18.9 mPa·s at 25 °C |
| Solubility | Miscible with water, ethanol, acetone, chloroform |
| Pka | 9.50 at 25 °C |
| Refractiveindex | 1.4539 at 20 °C |
| Logp | -1.31 |
| Ph | 11.5 (1% aqueous solution) |
As an accredited Monoethanolamine (MEA) factory, we enforce strict quality protocols—every batch undergoes rigorous testing to ensure consistent efficacy and safety standards.
| Packing | Monoethanolamine (MEA) is supplied in 200 L steel drums or 1,000 kg IBC totes, tightly sealed for industrial handling. |
| Container Loading (20′ FCL) | Container Loading (20′ FCL) for Monoethanolamine (MEA): drums/IBCs secured, sealed, labeled corrosive, with full hazardous documentation for ocean transport. |
| Shipping | Monoethanolamine (MEA), UN 2491, is a Class 8 corrosive liquid, Packing Group III. Ship in UN-approved, corrosion-resistant drums, IBCs, or tanks. Label and placard as corrosive. Keep containers closed, away from acids, oxidizers, and moisture. Provide SDS and emergency response information. Follow IMDG, IATA, ADR, and 49 CFR rules. |
| Storage | Store MEA in a cool, dry, well-ventilated, fire-resistant area in tightly closed carbon steel or stainless steel containers. Keep above 10°C to prevent crystallization. Avoid copper, brass, aluminum, acids, oxidizers, and ignition sources. Blanket with dry nitrogen to limit moisture/CO₂ absorption. Use secondary containment, grounding, and spill kits; inspect regularly for leaks and corrosion. |
| Shelf Life | Typically 2 years when stored sealed, cool, and dry, away from moisture, air, acids, and oxidizers; MEA is hygroscopic and CO2-sensitive. |
Industrial MEA-based acid gas removal trains for natural gas, refinery off-gas, and ammonia synthesis gas operate within a narrow concentration window because carbon steel absorber and regenerator circuits are susceptible to amine stress corrosion cracking when free amine concentration and acid-gas loading exceed thresholds identified in API RP 945-2003. The lean MEA solution is maintained at 15–20 wt% MEA in demineralized water. An upper operating ceiling of 25 wt% is applied to carbon steel units without post-weld heat treatment or stainless cladding on the hot circuit. Rich amine loading is controlled at 0.30–0.40 mol acid gas per mol MEA; loadings above 0.45 mol/mol accelerate wall loss in the rich/lean exchanger and regenerator overhead circuit. The absorber is operated at 35–45 °C and 40–60 barg, depending on feed gas composition. Regenerator bottom temperature is limited to 120–126 °C with saturated steam at 0.5–0.8 barg. A continuous slipstream reclaimer of 1–3% of circulating inventory is maintained with sodium carbonate addition to recover free amine from heat-stable salts formed by oxygen ingress and acid gas degradation. Materials selection follows ISO 15156-1:2020 for sour service; weld procedures are qualified under NACE SP0472-2010 to reduce wet H2S and carbonate cracking.
| Process variable | Typical operating window | Reference basis |
|---|---|---|
| Lean MEA concentration | 15–20 wt% | API RP 945-2003 carbon steel service ceiling |
| Rich acid-gas loading | 0.30–0.40 mol/mol | Gas Processing Suppliers Association engineering data |
| Absorber inlet temperature | 35–45 °C | Vendor H2S slip guarantee basis |
| Regenerator bottom temperature | 120–126 °C | Saturated steam 0.5–0.8 barg |
| Reclaimer slipstream | 1–3% of circulating volume | API RP 945-2003 heat-stable salt control |
Downstream, treated gas is certified against ISO 13686:2013 quality designation H, with H2S below 4 ppmv and CO2 below 50 ppmv before dehydration. Terminal outputs are pipeline-spec natural gas, LNG feed after molecular-sieve dehydration, and hydrotreater make-up hydrogen after methanation. The acid gas stream is routed to a Claus unit; MEA selectivity is lower than formulated methyldiethanolamine solvents, which is why the unit is typically selected where deep CO2 removal is required alongside H2S.
In dry-grinding of Portland clinker in closed-circuit ball mills, MEA is injected as one component of a processing-addition package at 0.02–0.05 wt% of clinker feed. The material functions by neutralizing electrostatic surface charges on freshly fractured clinker particles, reducing ball and liner coating, and stabilizing separator feed before classification. The dosage is lower than triethanolamine-based packages because MEA has a lower molecular weight and higher amine value per kilogram, which produces a measurable pH shift at the mill inlet. Compliance is assessed under ASTM C465-23 for processing additions; compressive strength retention is verified at 7 days and 28 days according to ASTM C109/C109M-21, while fineness is tracked by ASTM C204-18. Cement meeting EN 197-1:2011 and ASTM C150-22 is the release basis.
On the production line, MEA is dosed through an atomizing lance at the mill inlet or sprayed onto the first-compartment clinker bed. Ball mills with high-efficiency dynamic separators and closed-circuit operation show throughput gains of 8–12% at constant Blaine fineness in plant trials where the amine package is adjusted to mill ventilation and clinker temperature. For vertical roller mills, published data for MEA-only grinding aid formulations remains limited; most published evidence derives from triethanolamine and triisopropanolamine blends, and the MEA contribution must be verified against the specific clinker SO3 and alkali sulfate balance. The finished cement types include CEM I 42.5 N/R, CEM II/A-M 42.5, and ASTM C150 Type I/II portland cement.
MEA functions in emulsifiable metalworking fluid concentrates as a primary alkalinity donor and ferrous corrosion inhibitor. The neat concentrate is formulated with 2–8 wt% MEA, adjusted to the acid value of the naphthenic oil, tall oil fatty acid, or sulfonate emulsifier being neutralized. The working emulsion is prepared by diluting the concentrate to 5–10 vol% in water, producing a pH window of 9.0–9.5; this pH passivates ferrous surfaces but is not suitable for neat magnesium or zinc-rich alloys because alkaline attack can occur at sump temperatures above 60 °C. The classification for metal removal fluids is given under ISO 6743-7, and ferrous corrosion performance is tested by the Herbert corrosion test under DIN 51360-2. The concentrate itself is assessed under DIN 51360-1 for emulsion stability and oil separation. The MEA raw material registration under EU No 1907/2006 and classification under EU No 1272/2008 as Skin Corr. 1B H314 and Eye Dam. 1 H318 require closed transfer in concentrate plants.
During manufacture, MEA is added to the emulsifier package before oil dilution under high-shear rotor-stator mixing at 40–60 °C. The addition order controls the neutralization exotherm and prevents localized gel formation. Nitrite-based corrosion inhibitors are excluded from MEA concentrates because nitrosating conditions in acidic sumps can generate N-nitrosamine; relevant restriction is addressed under TRGS 611. Terminal finished products include semi-synthetic cutting fluids for central machining systems, tapping fluids for thread forming, and water-miscible grinding coolants. Where mist formation is possible during high-speed machining, local exhaust ventilation is specified because MEA has higher vapour pressure than triethanolamine at the same sump temperature.
When MEA is selected as the counterion for phenoxyalkanoic acid active ingredients, the neutralization reaction is run as a controlled batch process rather than a simple pH adjustment. For technical 2,4-D acid at 95% purity, MEA addition is approximately 0.26–0.28 kg per kg of technical acid, corresponding to a 1:1 molar ratio of carboxylic acid equivalent to amine. The final soluble concentrate may contain 40–60% by weight of the MEA salt expressed as acid equivalent, with the exact concentration fixed by the registration dossier. Technical acid is slurried in process water, and MEA is metered below the liquid surface with jacket cooling to control the neutralization exotherm. Batch temperature is maintained below 40 °C to prevent MEA vapour evolution, and endpoint pH is set at 7.5–8.5. Crystallization stability is checked at 0 °C and 54 °C, and pH is measured by CIPAC MT 75.3.
Registrations fall under EU Regulation (EC) No 1107/2009 for plant protection products and maximum residue limits under EU Regulation (EC) No 396/2005. In the United States, residues of 2,4-D are regulated under 40 CFR 180.142. The terminal product type is a soluble liquid (SL) formulation for cereals, pasture, and rights-of-way vegetation management; this is distinct from ester emulsifiable concentrates and does not require aromatic hydrocarbon solvent. MEA salt selection reduces dust and odour issues compared with dimethylamine salt handling at the mixer.
Replacement of diethanolamine with MEA in fatty acid methyl ester condensation changes the melting profile and thickening efficiency of the resulting nonionic surfactant. The reaction is run at a methyl ester-to-MEA molar ratio of 1.0:1.05 to 1.0:1.10; sodium methoxide catalyst is charged at 0.1–0.3 wt% of total batch. Reactor temperature is ramped from 110 °C to 160 °C under vacuum at 50–200 mbar. Methanol vapour is taken overhead through a small fractionation column at 60–70 °C. The reaction is continued until free fatty acid is below 0.5 wt% and residual methanol is below 0.1 wt%. Feedstock moisture must be held below 0.1 wt% because water deactivates the methoxide catalyst and produces fatty acid soap side products. The vacuum system is typically a liquid-ring pump with methanol recovery, and a slow nitrogen sparge is maintained to control colour development.
Finished monoethanolamide is post-dosed into liquid dishwashing detergents at 1–3 wt% to build viscosity and stabilize foam. Neat amide solidifies at 70–80 °C, so heated storage and transfer at 55–65 °C or a hydrotrope system is required. Regulatory compliance for the finished detergent is governed by EU Regulation (EC) No 648/2004; the MEA raw material and the amide are registered under EU No 1907/2006. Ready biodegradability of the amide is measured under OECD 301B. Terminal product types include hand dishwashing liquids, hard surface cleaners, industrial degreasers, and laundry liquids where high-foam nonionic systems are specified.
A waterborne copper ethanolamine wood preservative concentrate is produced by reacting basic copper carbonate with MEA. The MEA-to-copper molar ratio is set at 4:1, and MEA represents 20–30 wt% of the neat concentrate. Water is charged first, MEA is added, and basic copper carbonate is fed slowly under high-shear agitation at 50–60 °C. Carbon dioxide evolution is controlled by staged powder addition and vacuum; the reaction endpoint is visual clarity and pH 9.5–10.5. At ratios below 4:1, residual carbonate solids remain and copper availability drops. After dissolution, the concentrate is cooled to 30–35 °C and post-blended with quaternary ammonium compound or tebuconazole/azole co-biocide depending on the target product type.
The working preservative solution is diluted to 1–3% copper concentration and applied by vacuum-pressure impregnation. For Use Category UC4B ground-contact lumber, a copper retention target of 6.4 kg/m³ is common under AWPA U1-22. The preservative system is specified under AWPA P5-22 in the United States and under EN 599-1:2013 within the European biocidal products framework established by EU No 528/2012. Terminal products include ACQ-C and copper azole wood treated softwood lumber, utility poles, roundwood posts, and cross arms.
| Jurisdiction | Standard or regulation | MEA-relevant provision |
|---|---|---|
| United States | AWPA P5-22 / AWPA U1-22 | Waterborne copper-amine preservative retention for UC4B ground contact |
| European Union | EU No 528/2012 / EN 599-1:2013 | Active substance approval and treated article labelling obligations |
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Monoethanolamine (MEA, CAS 141-43-5) is a clear, hygroscopic primary alkanolamine supplied for acid-gas absorption, pH buffering, and chemical synthesis. Commercial model designations commonly include technical grade, low-iron grade, and anhydrous chemical grade; the main specification differentiators are trace iron, water, and color. The molecular formula is C₂H₇NO, and the molar mass is 61.08 g/mol. At 20 °C, the liquid has a density near 1.012 g/cm³, viscosity near 24 mPa·s, boiling point 170.8 °C at 101.3 kPa, freezing point 10.3 °C, and conjugate-acid pKa 9.50 at 25 °C. Because the molecule contains both a primary amine and a primary hydroxyl group, it reacts with carbon dioxide, epoxides, fatty acid esters, and sulfonic acids while retaining substantial water solubility.
| Parameter | Control Value | Unit | Test Method |
|---|---|---|---|
| MEA assay | ≥ 99.0 | % by mass | internal GC-FID |
| Water content | ≤ 0.30 | % by mass | ASTM E203 |
| Color, Pt-Co | ≤ 15 | APHA | ASTM D1209 |
| Density at 20 °C | 1.012–1.018 | g/cm³ | ASTM D4052 |
| Boiling range 5–95 mL | 166–173 | °C | ASTM D1078 |
Low-iron MEA is controlled to ≤ 0.5 ppm total iron for alkoxylation, pharmaceutical intermediate, and electronic-grade applications. Technical-grade MEA is typically packaged in 205 L epoxy-lined steel drums, 1000 L intermediate bulk containers, and bulk isotank containers with nitrogen blanketing. The product is classified under EU CLP Annex VI index number 603-030-00-8 as acute toxicity category 4 and skin corrosion category 1B; EU supply requires REACH registration and exposure-scenario documentation.
Aqueous MEA forms carbamate directly with carbon dioxide through the primary amine site, consuming 2 mol MEA per mol CO₂ at low loading. Diethanolamine (DEA), a secondary amine, also forms carbamate but with slower kinetics. Triethanolamine (TEA), a tertiary amine, does not form a stable carbamate and follows a base-catalysed carbon dioxide hydration route. On a per-kilogram basis, MEA provides 16.4 mol acid-neutralizing capacity versus 9.5 mol/kg for DEA and 6.7 mol/kg for TEA. The higher alkalinity per unit mass, lower molar mass, and greater vapor pressure of MEA make it more reactive in packed columns but also more prone to vapor-phase amine losses and corrosive behavior in hot lean/rich piping.
| Property | Monoethanolamine | Diethanolamine | Triethanolamine |
|---|---|---|---|
| CAS number | 141-43-5 | 111-42-2 | 102-71-6 |
| Molar mass | 61.08 g/mol | 105.14 g/mol | 149.19 g/mol |
| Boiling point at 101.3 kPa | 170.8 °C | 268.8 °C | 335.4 °C decomposition |
| pKa at 25 °C | 9.50 | 8.88 | 7.76 |
| Neutralization capacity | 16.4 mol/kg | 9.5 mol/kg | 6.7 mol/kg |
| CO₂ reaction route in aqueous solution | Fast carbamate formation | Slower carbamate formation | Carbonate/bicarbonate route, no carbamate |
In low-pressure natural gas and refinery off-gas service, MEA is circulated as a 15–20 wt% aqueous solution. The absorber is generally a countercurrent tray or structured-packing column operated at 1–7 MPa with lean solvent inlet temperature 35–40 °C. Rich-solvent loading is held between 0.40 and 0.45 mol CO₂ per mol MEA to limit corrosion, while lean loading is maintained at 0.10–0.15 mol/mol by controlling reboiler steam. The regeneration skid heats rich MEA through a plate-and-frame lean/rich exchanger to 95–100 °C before distillation in a reboiled stripper at 115–125 °C and 0.07–0.15 MPa overhead pressure. Reflux ratios are held at 0.5–1.5 mol/mol overhead vapour to reduce amine carryover.
Carbon steel is acceptable for stress-relieved contactor shells, but hot lean/rich piping requires 304L stainless steel or post-weld heat treatment. Copper and copper alloys are excluded from MEA service because the amine dissolves copper oxides and induces galvanic corrosion. The main operational boundary is thermal degradation. Above 125 °C, MEA can degrade by carbamate polymerization and ring closure to 2-oxazolidinone, with additional heat-stable salt formation from formate, acetate, and thiosulfate. Reclaimers on a 2–4% slipstream of lean inventory remove nonvolatile degradation products. Mechanical filters with 10 µm elements remove iron sulfide particulates that otherwise accumulate in absorber sumps. These operating limits differentiate MEA from formulated methyldiethanolamine blends, which tolerate higher acid-gas loadings and lower regeneration energy but exhibit slower CO₂ uptake under low-pressure flue-gas conditions.
In post-combustion CO₂ capture from pulverized-coal flue gas, the solvent is typically 30 wt% MEA, not 15–20 wt%. Specific reboiler duty is reported in the range 3.2–3.8 MJ/kg CO₂ for conventional MEA without advanced heat integration. Flue gas is cooled to 40–50 °C and passes through a water-wash section to control amine vapor emissions. Rich/lean loading difference is narrowed to 0.25–0.35 mol CO₂/mol amine to reduce degradation, while stripper reboiler temperature remains 120–125 °C. Oxidative degradation from flue-gas oxygen produces formate, glycolate, and ammonia; iron and copper ions accelerate oxidative breakdown, requiring low-iron makeup MEA and upstream filtration.
If the process goal is enrichment of acid gas for sulfur recovery and carbon dioxide is to remain in the treated stream, MEA is not the preferred solvent. Tertiary amines or formulated MDEA solutions are selected because they absorb hydrogen sulfide more selectively relative to carbon dioxide under absorber residence times of 1–2 s. MEA reacts rapidly with carbon dioxide, lowering the H₂S/CO₂ selectivity and increasing solvent regeneration duty. Published data for specific high-pressure selective MEA configurations is limited; general design practice is to use MEA only when bulk removal of both acid gases is acceptable. The same limitation applies to syngas treating ahead of ammonia synthesis, where residual CO₂ breakthrough specifications below 10 ppmv require a secondary guard bed or hot potassium carbonate unit downstream of the MEA absorber.
Neutralization of linear alkylbenzene sulfonic acid in detergents and personal-care concentrates uses MEA at stoichiometric ratio 1.0 mol amine per mol sulfonic acid. At 25 °C, addition of MEA to a 45 wt% active surfactant paste raises pH to 7.5–8.5; the low molar mass of MEA yields the highest alkalinity reserve per unit mass among common alkanolamines. In metalworking fluid concentrates, MEA is added at 0.5–2.0 wt% to maintain pH 9.0–9.5 and to buffer acidic oxidation products. The selection of MEA over TEA in these systems reduces the mass of base required and increases water compatibility, but MEA has higher vapor pressure and a stronger ammoniacal odor. Formulations with airborne exposure limits below 3 ppm may require ventilation or replacement by DEA. MEA is not combined with nitrosating agents or nitrite corrosion inhibitors because of potential nitrosamine formation under acidic storage conditions.
In closed-circuit cement mills, monoethanolamine is introduced at 0.02–0.05% by mass of clinker feed to reduce agglomeration on grinding media and improve separator efficiency. The amine adsorbs onto silicate surfaces and reduces electrostatic surface charge, but the magnitude of Blaine specific-surface change depends on mill ventilation, separator speed, and clinker tricalcium aluminate content. Published data for specific open-circuit mill configurations is limited; plant trials are required to establish the dosage window. Overdosing above 0.10% by mass may depress early-age compressive strength through air entrainment and calcium hydroxide buffering. The material is typically sprayed onto the mill feed belt as a 10–20 wt% aqueous solution using a peristaltic metering pump.
The liquid is hygroscopic and absorbs atmospheric carbon dioxide and water, which increases viscosity and precipitates carbamate salts. Storage tanks for anhydrous MEA use 316L stainless steel or lined carbon steel with nitrogen blanketing at 0.5–1.0 kPa positive pressure. Heat tracing maintains tank temperature above 15 °C because the freezing point is 10.3 °C; pumps and transfer lines are heat-traced to 20–25 °C. Centrifugal pumps with mechanical seals made of EPDM or PTFE are specified. Copper, zinc, and aluminum wetted parts are prohibited. Under prolonged exposure to air at relative humidity above 60%, water content can rise by 0.1–0.2 wt% in an open drum within 24 h. Transfer filtration through 5 µm polypropylene elements is performed before use in analytical or pharmaceutical processes.
