Methyldiethanolamine solutions MDEA

Rgure 2-70. Viscosity of Diglycolamlne and methyldiethanolamine solutions. MDEA data from Teng et al. (1994) DGA data trom Jefferson Chemical Co. (1969)... 

Tertiary amines cannot form carbamates, but they react with CO2 in aqueous solvents to form hydrogencarbonate (3.20). Yu and Astarita [29] studied the kinetics of the absorption of carbon dioxide in MDEA (bis(2-hydroxyethyl) methylamine 77-methyldiethanolamine) solutions and... 

Methyldiethanolamine (MDEA) and solutions of MDEA have increased in use for gas treating (150,151). Additional gas treating capacity can often be obtained with the same working equipment, because of the higher amine concentrations that can be used. 

The solvent used for the absorption/desorption experiments is a 99% methyldiethanolamine (MDEA) from Sigma-Aldrich in a 50 wt% distilled water solution. 

Aqueous alkanolamine solutions are frequently used for removal of acidic gases such as carbon dioxide and hydrogen sulfide from gas streams in the natural gas, synthetic, and refinery industries. Several options are available for removing acid gases, but by far the most popular is the absorption by amine based solvents such as monoethanolamine (MEA), diglycolamine (DGA), diethanolamine (DEA), di-isopropanolamine (DIPA), triethanolamine (TEA), N-methyldiethanolamine (MDEA), 2-amino-2-methyl-l-propanol (AMP), and 2-piperidineethanol (2-PE) in reversible absorption-regeneration processes [1]. 

Kaewsichan L, Al-hofersrai O, Yesavage VF, Selim MS. Predictions of the solubility of acid gasses in monoethanolamine (MEA) and methyldiethanolamine (MDEA) solutions using the electrolye-UNIQUAC model. Fluid Phase Equdih 2001 183 184 159-71. 

To remove the carbon dioxide, the gas mixture is led in counter-flow through a water solution of methyldiethanolamine, MDEA. Carbon dioxide is absorbed and is after-... 

Methyldiethanolamine (MDEA) is often used for the removal of CO2 from synthesis gases produced in steam reformers (cf Section 5.2.2.1). The aqueous solution of 35 to 50 wt-% MDEA reacts with CO2 ... 

There are a number of cases of industrial gas cleanups where two (A and B) or more gases are being simultaneously absorbed in the Uquid. The nature of mass transport, and therefore separation, will depend on how ficist each species reacts with the nonvolatile reactive species C (often the species C has some volatility, e.g. monoetha-nolamine). Each of gas species A and B can either react slowly or have a fast or instantaneous reaction with C. Thus, there can be a number of combinations, many of which are treated in Astarita et al. (1983). We consider here a particular case of considerable industrial importance, namely simultaneous absorption of H2S and CO2 into a reactive aqueous solution containing, say, methyldiethanolamine (MDEA). We want to show how the different rates of absorption lead to a high selectivity of H2S over CO2. The specific reactions are (Haimour et al, 1987)... 

Attributing corrosion to simple acid gas attack explains several observed corrosion phenomena. For example, primary amines, such as monoethanolamine (MEA) and Diglyco-lamine (DGA), are more corrosive than secondary and tertiary amines because in amine systems employing primary amines, which are difficult to strip, high concentrations of amine-acid gas salts are present in the hottest areas of the process. Conversely, methyldiethanolamine (MDEA), a tertiary amine, is easily stripped of both CO2 and H2S. Therefore, it is less corrosive because the bulk of the acid gas is evolved fiom solution at a lower temperature. 

Use of an aqueous methyldiethanolamine (MDEA) solution as a selective solvent (see Chapter 2) for hydrogen sulfide removal in tail gas cleanup has been described by Meissner (1983). With this solvent an overall conversion, including the Claus unit, of 99.9% of the H2S fed to the Claus unit is attainable. However, the treated gas contains some residual H2S, which may require incineration before discharge to the atmosphere. 

H. Arcis, L. Rodier, K. Ballerat-BusseroUes, J.Y. Coxam, Modeling of (vapor-l- liquid) equilibrium and enthalpy of solution of carbon dioxide (CO2) in aqueous methyldiethanolamine (MDEA) solutions. J. Chem. Thermodyn. 41(6), 783-789 (2009)... 

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