Monoethanolamine (C2H7NO), Diethanolamine (C4H11NO2), and Triethanolamine (C6H15NO3) are three basic ethanolamines produced in large scale by reacting ammonia and ethylene oxide.
Chemical reactions equations:
- CH2-CH2-O + NH3 → NH2CH2CH2OH MEA
- CH2-CH2-O + NH2CH2CH2OH → NH(CH2CH2OH)2 DEA
- CH2-CH2-O + NH(CH2CH2OH)2 → N(CH2CH2OH)3 TEA
Process description of ethanolamines production:
Ammonia mixed with water to form aqueous ammonia solution with a concentration ranging from 25-30% and mixed with ethylene oxide in a stirred tank reactor. The reaction is exothermic so the reactors are provided with jackets and water circulated to remove the generated heat to maintain the reaction temperature. The fed ratio of the ammonia and ethylene oxide directly affects the product formation to MEA, DEM or TEM. Based on the product requirements the raw material fed ratio automatically adjusted during the reaction operation by the control valve opening by the DCS. In general, to obtain high monoethanolamine product in single reaction cycle high ammonia to ethylene fed ratio is the favourable condition. Unreacted ammonia is recycled from the ammonia flash separator. Three individual towers separate MEA, DEA and TEA from the reactor product stream and a provision of recycling DEA and MEA to the reactor is provide to converted into TEA or DEA. Di and Tri separation tower operate under vacuum to prevent decomposition problem.
Process flow diagram ethanolamines
Industrial application of ethanolamines:
- Aqueous ethanolamines are used as scrubbing agents to absorb sulphur compound (H2S, SO2) in gas like natural gas, flue gas, and process gases. Packed bed absorbers are used for the scrubbing operation called as sweetening process in case of natural gas treatment.
- Due to the basic(high pH) property of ethanolamines, ammonia in the form of amine functional group reacts with acids likes CO2 and CO. CO2 purification units and synthesis gas units use aqueous ethanolamines in continuous scrubbing process because these ethanolamines are regenerable. Diethanolamine dissolves in water to form aqueous solutions having absorption factor 0.4 towards carbon dioxide.