Monoethanolamine

Monoethanolamine is a somewhat viscous hygroscopic liquid with an ammoniacal odor. 

It is miscible with water and many organic solvents. Its molecule contains both a hydroxyl and an amine group, thus producing derivatives that have characteristics of both types of compounds. It is used as a softener and conditioning agent, and in the recovery and extraction of carbon dioxide and hydrogen sulfide from industrial gases. Its soaps with fatty acids are excellent emulsifiers for waxes. It is also utilized as an intermediote In the manufacture of rubber accelerators and dyestuffs. 

Refractive index at 20 C SpeciAe gravity at 20 (20 C Specific heat at 30 C Surface tension at 20 0 Viscosity at 20 C Vapor pressure at 20 C Weight per gallon at 20 C 

Boiling range at 760 mm Not less than 90% over Color.  

The acute oral toxicity value in animals was low to moderate. An oral LD50 value in rats is 500 mg/kg (NIOSH 1986). 

Structure HO—CH2—CH2—NH2 the amine contains a primary alcoholic —OH group Synonyms ethanolamine 2-aminoethanol jd-aminoethyl alcohol 2-hydroxyethyla-mine colamine 

Monoethanolamine is used as a dispersing agent for agricultural chemicals, in the 

Colorless, viscous liquid with a mild ammo-niacal odor hygroscopic density 1.018 at 20°C (68°F) bp 171°C (339°F) solidifies at 10.3°C (50°F) miscible with water, alcohol, and acetone strongly alkaline, pH 12.05 (0.1 N aqueous solution) absorbs CO2. 

Monoethanolamine causes severe irritation of the eyes and mild to moderate irritation of the skin. The pure liquid caused redness and swelling when applied to rabbits skin. The acute oral toxicity of this compound was low in animals. The toxic symptoms included somnolence, lethargy, muscle contraction, and respiratory distress. The oral LD50 values showed a wide variation with species. 

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Here the ethylene oxide undergoes parallel reactions, whereas the monoethanolamine undergoes a series reaction to diethanolamine and triethanolamine. 

Example 2.4 Monoethanolamine is required as a product. This can be produced from the reaction between ethylene oxide and ammonia ... 

The secondary reactions are parallel with respect to ethylene oxide but series with respect to monoethanolamine. Monoethanolamine is more valuable than both the di- and triethanolamine. As a first step in the flowsheet synthesis, make an initial choice of reactor which will maximize the production of monoethanolamine relative to di- and triethanolamine. 

Solution We wish to avoid as much as possible the production of di- and triethanolamine, which are formed by series reactions with respect to monoethanolamine. In a continuous well-mixed reactor, part of the monoethanolamine formed in the primary reaction could stay for extended periods, thus increasing its chances of being converted to di- and triethanolamine. The ideal batch or plug-flow arrangement is preferred, to carefully control the residence time in the reactor. 

Cmea = molar concentration of monoethanolamine Cdea = molar concentration of diethanolamine... 

The use of an excess of ammonia is home out in practice. A mole ratio of ammonia to ethylene oxide of 10 1 3delds 75 percent monoethanolamine, 21 percent diethanolamine, and 4 percent triethanolamine. Using equimolar proportions under the same reaction conditions, the respective proportions become 12, 23, and 65 percent. 

Another possibility to improve selectivity is to reduce the concentration of monoethanolamine in the reactor by using more than one reactor with intermediate separation of the monoethanolamine. Considering the boiling points of the components given in Table 2.3, then separation by distillation is apparently possible. Unfortunately, repeated distillation operations are likely to be very expensive. Also, there is a market to sell both di- and triethanolamine, even though their value is lower than that of monoethanolamine. Thus, in this case, repeated reaction and separation are probably not justified, and the choice is a single plug-flow reactor. 

An initial guess for the reactor conversion is very difficult to make. A high conversion increases the concentration of monoethanolamine and increases the rates of the secondary reactions. As we shall see later, a low conversion has the effect of decreasing the reactor capital cost but increasing the capital cost of many other items of equipment in the flowsheet. Thus an initial value of 50 percent conversion is probably as good as a guess as can be made at this stage. 

For example, hydrogen sulfide and carbon dioxide can be removed from natural gas by reaction with monoethanolamine in an absorber according to the following reactions ... 

These reactions can be reversed in a distillation column. This releases the hydrogen sulfide and carbon dioxide for further processing. The monoethanolamine can then be recycled. 

Reaction with Aldehydes and Ketones. Formaldehyde combines with primary and secondary alkanolamines in the presence of alkali to give methylol derivatives. For the reaction of monoethanolamine with formaldehyde (12), the reaction scheme shown in Figure 1 occurs. 

Fig. 1. Reaction of formaldehyde with monoethanolamine. If two moles of monoethanolamine react with three moles of formaldehyde, the bisoxazohdine is the only product isolated. A 1 1 mole ratio of monoethanolamine to formaldehyde produces a mixture of the triazine and the bisoxazohdine.

Monoalkanolamines are converted by carbon disulfide into 2-metcaptothia2olines. Ethyleneurea (2-imida2ohdinone) can be prepared by heating a mixture of monoethanolamine and urea for several hours. 

In certain cases, alkanolamines function as reduciag agents. For example, monoethanolamine reduces anthraquiaone to anthranols, acetone to 2-propanol, and azobenzene to aniline (17). The reduction reaction depends on the decomposition of the alkan olamine iato ammonia and an aldehyde. Sinulady, diethan olamine converts o-chloronitrobenzene to 2,2 -dichloroazobenzene and y -dinitrobenzene to 3,3 -diamiQoazobenzene. 

Chemical Processing Intermediates and Other Applications. Monoethanolamine can be used as a raw material to produce ethylenedianiine. This technology has some advantages over the ethylene dichloride process in that salts are not a by-product. Additional reactions are requked to produce the higher ethyleneamines that are normally produced in the ethylene dichloride process. 

Expert Panel of the Cosmetic Ingredient Review, Final Report on the Safety Assessment for Diisopropano/amine, Triisopropano/amine, Isopropano/amine, Mixed Isopropano/amines, Sept. 26, 1986 Final Report for the Safety Assessment for Triethanolamine, Diethanolamine, Monoethanolamine, May 19, 1983. 

A.lkanolamine Process. Carbon dioxide is an acidic gas that reacts reversibly with aqueous alkaline solution to form a carbonate adduct. This adduct decomposes upon the addition of low level heat faciUtating CO2 removal. An aqueous solution of 15—20 wt % monoethanolamine (MEA) was the standard method for removing CO2 in early ammonia plants. 

GirhotolAmine Process. This process developed by the Girdler Corporation is similar in operation to the alkali carbonate processes. However, it uses aqueous solutions of an ethanolamine, ie, either mono-, di-, or triethanolamine. The operation of the Girbotol process depends on the reversible nature of the reaction of CO2 with monoetbanolamine [141-43-5] to form monoethanolamine carbonate [21829-52-7]. 

SolubiHty of carbon dioxide in ethanolamines is affected by temperature, amine solution strength, and carbon dioxide partial pressure. Information on the performance of amines is available in the Hterature and from amine manufacturers. Values for the solubiHty of carbon dioxide and hydrogen sulfide mixtures in monoethanolamine and for the solubiHty of carbon dioxide in diethanolamine are given (36,37). SolubiHty of carbon dioxide in monoethanolamine is provided (38). The effects of catalysts have been studied to improve the activity of amines and provide absorption data for carbon dioxide in both mono- and diethanolamine solutions with and without sodium arsenite as a catalyst (39). Absorption kinetics over a range of contact times for carbon dioxide in monoethanolamine have also been investigated (40). 

Of the four commercial processes for the purification of carbon monoxide two processes are based on the absorption of carbon monoxide by salt solutions, the third uses either low temperature condensation or fractionation, and the fourth method utilizes the adsorption of carbon monoxide on a soHd adsorbent material. AH four processes use similar techniques to remove minor impurities. Particulates are removed in cyclones or by scmbbing. Scmbbing also removes any tars or heavy hydrocarbon fractions. Acid gases are removed by absorption in monoethanolamine, hot potassium carbonate, or by other patented removal processes. The purified gas stream is then sent to a carbon monoxide recovery section for final purification and by-product recovery. 

TABLE 23-8 Correlation of Kgo for Absorption of CO by Aqueous Solutions of Monoethanolamine in Packed Towers ... 

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