Methyl diethanolamine
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| Names | |
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Preferred IUPAC name
2,2'-(Methylazanediyl)di(ethan-1-ol)
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| Other names
Bis(2-hydroxyethyl)(methyl)amine
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| Identifiers | |
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3D model (JSmol)
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| 1734441 | |
| ChemSpider | |
| ECHA InfoCard | 100.003.012 |
| EC Number | 203-312-7 |
| MeSH | N-methyldiethanolamine |
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PubChem CID
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| RTECS number | KL7525000 |
| UNII | |
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| Properties | |
| C5H13NO2 | |
| Molar mass | 119.16 g·mol−1 |
| Appearance | Colorless liquid |
| Odor | Ammoniacal |
| Density | 1.038 g mL−1 |
| Melting point | −21.00 °C; −5.80 °F; 252.15 K |
| Boiling point | 247.1 °C; 476.7 °F; 520.2 K |
| Miscible | |
| Vapor pressure | 1 Pa (at 20 °C) |
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Refractive index (nD)
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1.4694 |
| Viscosity | 101 mPa s (at 20°C) |
| Pharmacology | |
| Oral | |
| Hazards | |
| GHS pictograms |  |
| GHS signal word | WARNING |
| H319 | |
| P305+351+338 | |
| NFPA 704 | |
| Flash point | 127 °C (261 °F; 400 K) |
| 410 °C (770 °F; 683 K) | |
| Explosive limits | 1.4-8.8% |
| Lethal dose or concentration (LD, LC): | |
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LD50 (median dose)
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1.945 g kg−1(oral, rat) |
| Related compounds | |
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Related alkanols
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Related compounds
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Diethylhydroxylamine |
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Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
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 (what is   ?) |
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| Infobox references | |
Methyl diethanolamine is a clear, colorless or pale yellow liquid with an ammonia odor. It is miscible with water, alcohol and benzene. Methyl diethanolamine is also known as N-methyl diethanolamine and more commonly as MDEA. It has the formula CH3N(C2H4OH)2. MDEA is a tertiary amine and is widely used as a sweetening agent in chemical, oil refinery, syngas production and natural gas.
Similar compounds are monoethanolamine (MEA), a primary amine, and diethanolamine (DEA), a secondary amine, both of which are also used for amine gas treating. MDEA's defining characteristic when compared to these other amines is its ability to preferentially remove H2S (and strip CO2) from sour gas streams..
MDEA's popularity as a solvent for gas treating stems from several advantages it has when compared to other alkanolamines. One of these advantages is a low vapor pressure, which allows for high amine compositions without appreciable losses through the absorber and regenerator. MDEA is also resistant to thermal and chemical degradation and is largely immiscible with hydrocarbons. Lastly, MDEA has a relatively low heat of reaction with hydrogen sulfide and carbon dioxide, which allows for lower reboiler duties, thus lower operating costs.
MDEA is less reactive towards CO2, but has an equilibrium loading capacity approaching 1 mole CO2 per mole amine. It also requires less energy to regenerate. To combine the advantages of MDEA and the smaller amines, MDEA is usually mixed with a catalytic promoter such as piperazine, PZ, or a fast reacting amine such as MEA to retain reactivity, but lower regeneration costs. Activated MDEA or aMDEA uses piperazine as a catalyst to increase the speed of the reaction with CO2. It has been commercially successful. Many tests have been conducted on the performance of MDEA/MEA or MDEA/Piperazine mixtures compared to single amines. CO2 production rates were higher than MEA for the same heat duty and total molar concentration when experiments were performed in the University of Regina pilot plant, which is a modeled after a natural gas plant. There were also insignificant trace amounts of degradation products detected. However, when the same control variables and tests were conducted at the Boundary Dam plant, the CO2 production rate for the mixed solvent was lower than MEA. This was a result of the reduction in the capacity of the solvent to absorb CO2 after degradation. Because the Boundary Dam plant is a coal-fired power plant, it operates under harsher environments and produces an impure flue gas containing, fly ash, SO2, and NO2 that are fed into carbon capture. Even with flue gas pretreatment, there is still enough to produce degradation products such as straight chain amines and sulfur compounds, which accumulate so it is no longer possible to regenerate MEA and MDEA. For these blends to be successful in reducing heat duty, their chemical stabilities must be maintained.
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