17.3 Ethanolamines

17.3.1 Reactions

• • Ethylene Oxide + Ammonia → Monoethanolamine

• Monoethanolamine + Ammonia → Diethanolamine

• DIethanolamine + Ammonia→ Triethanolamine

• The above reactions are series reaction scheme

• Reaction is exothermic

• Ammonia is in aqueous phase and ethylene oxide is in vapour state. Therefore, the reaction will be gas-liquid reaction

• Ethylene oxide is the limiting reactant

17.3.2 Process technology (Figure 17.2)

Figure 17.2 Flow sheet of production of ethanolamines

• • Ammonia is mixed with ammonia recycle stream from the process and pumped to the CSTR where liquid phase ammonolysis takes place.

• Ethylene oxide is compressed and fed to the CSTR.

• The CSTR operating pressure will be such that the feed (and product) mixtures do not vaporize and good liquid phase reaction can occur.

• The reactor is cooled using water in the cooling jacket as the reactions are mildly exothermic.

• The product stream is then sent to a flash unit that separates NH₃ + H₂O as a vapour stream and water + ethanolamines as a liquid stream.

• The ammonia + water stream is recycled to mix with the fresh ammonia and enter the reactor.

• The bottom product from ammonia flash unit is sent to a water separation tower that again removes dissolved ammonia in the ethanolamine rich solution. Once again ammonia + water are generated and this stream is also recycled to mix with fresh ammonia feed.

• The bottom product consisting of crude mixture of ethanolamines and heavy ends.

• This mixture is fed to a monoethanolamine tower first to separate the monoethanol amine from the other two and heavy ends.

• The bottom product from the first distillation tower then enters the second and third distillation towers which are operated under vacuum to produce diethanolamine and triethanolamine as top products. The bottom product from the last distillation tower is the heavy ends product.