Methyldiethanolamine (N-Methyldiethanolamine, MDEA) Storage & Tank Compatibility

Storing Methyldiethanolamine (N-Methyldiethanolamine, MDEA)? Start Here

Methyldiethanolamine, also called N-methyldiethanolamine or MDEA (C₅H₁₃NO₂), is a colorless, water-miscible tertiary alkanolamine that pairs a hindered amine nitrogen with two hydroxyl groups. That structure gives it a useful selectivity: it absorbs hydrogen sulfide quickly while taking up carbon dioxide more slowly, which is why MDEA is the workhorse solvent for selective gas sweetening in refineries, natural-gas plants, and ammonia and syngas units. It also serves as a pH buffer and neutralizer, a corrosion inhibitor, and a building block for surfactants and pharmaceuticals. Because it is mildly alkaline and reactive toward certain metals and elastomers, the material of construction matters: the wrong seal compound or a copper-bearing alloy will degrade, contaminate the amine, or shorten service life. A tank, gasket, and fitting package genuinely rated for amine duty protects both the chemical and the people handling it.

Can you store methyldiethanolamine in a poly tank?

Yes. Methyldiethanolamine is compatible with polyethylene. Published resistance charts rate amines, alkanolamines, alcohols, and glycols as Resistant on both HDPE and crosslinked (XLPE) polyethylene at ambient temperature, and aqueous ammonia (a close chemical analog) is likewise rated Resistant. A chemical-service poly tank is a sound, economical choice for bulk MDEA storage and make-up. Its specific gravity is only about 1.04, so a standard 1.5 specific-gravity tank carries the load comfortably. Specify EPDM gaskets rather than Viton/FKM, and keep copper, brass, bronze, and aluminum out of all wetted hardware. For heated lean/rich amine loops, regenerator service, or high-purity applications, 316 stainless steel is the upgrade path; otherwise quality poly performs well for atmospheric storage and dispensing.

Material compatibility at a glance

Methyldiethanolamine is a mildly alkaline tertiary alkanolamine that is compatible with chemical-grade HDPE and XLPE polyethylene, polypropylene, and 304/316 stainless steel. Avoid copper alloys, aluminum, and fluoroelastomer (Viton/FKM) seals; specify EPDM gaskets.

Ratings: S suitable · C conditional / limited · U unsuitable. Verify against the cited resistance charts and your concentration/temperature before specifying.

The safety that actually matters

• Eye irritant (H319/H320): Causes serious eye irritation — chemical goggles and a face shield are required when handling or transferring.
• Reproductive concern (H361): Suspected of damaging fertility or the unborn child — minimize exposure and follow exposure controls for sensitive personnel.
• Combustible liquid: Flash point near 127 °C (260 °F); keep away from heat, sparks, and open flame and store cool and ventilated. Combustion can release nitrogen oxides and carbon monoxide.
• Mild base: Reacts exothermically with strong acids and oxidizers; segregate from acids, oxidizers, and isocyanates and add slowly when neutralizing.
• Mist and vapor: Volatility is very low, but provide local exhaust where mist or aerosol can form to limit eye and respiratory irritation.
• Spill control: Contain spills and prevent release to drains or surface water; the material is fully water-miscible and spreads readily.

Common questions

Is methyldiethanolamine compatible with HDPE and XLPE tanks?

Yes. Polyethylene resistance charts rate amines, alkanolamines, and alcohols as Resistant on HDPE and XLPE at ambient temperature. Use a chemical-service poly tank with EPDM seals; with a specific gravity near 1.04, a standard 1.5 SG tank is more than adequate.

What is the NFPA 704 rating for methyldiethanolamine?

NOAA CAMEO Chemicals lists Health 1, Flammability 1, and Instability 0, with no special hazard. It is a mildly hazardous, combustible liquid that is normally stable.

Which materials should be avoided with methyldiethanolamine?

Avoid copper, brass, bronze, and aluminum, which this alkaline amine corrodes, and avoid Viton/FKM elastomer seals, which amines attack. Specify EPDM gaskets and poly, polypropylene, or 316 stainless wetted parts instead.

Is methyldiethanolamine flammable?

It is a combustible liquid rather than a highly flammable one, with a closed-cup flash point near 127 °C (260 °F) and very low vapor pressure. Keep it away from heat and ignition sources and store it cool and ventilated.