• • In this lecture, we discuss upon the process technology for ethylene oxide and ethanolamines.

• Ethylene oxide is produced by the oxidation of ethylene using air.

• Ethanolamines are produced using the series reaction scheme of ethylene oxide with ammonia.

• Ethanolamines are significantly used as absorbents to remove CO₂ and H₂S from process gas streams.

17.2 Ethylene Oxide

17.2.1 Reactions

• • C₂ H₄ + 0.5 O₂→ CH₂ O.CH₂O

• Ethylene to air ratio: 3 – 10 %

• Side reaction products: CO₂ , H₂O

• Catalyst: Silver oxide on alumina

• Operating temperature and pressure: 250 – 300°C and 120 – 300 psi

• Supressing agent for side reactions: Ethylene dichloride

• Reaction is exothermic

 

17.2.2 Process technology (Figure 17.1)

Figure 17.1 Flow sheet of production of ethylene oxide

 

• • Air and ethylene are separate compressed and along with recycle stream are sent to the shell and tube reactor.

• The reactor is fed on the shell side with Dowtherm fluid that serves to maintain the reaction temperature. A dowtherm fluid is a heat transfer fluid , which is a mixture of two very stable compounds, biphenyl and diphenyl oxide. The fluid is dyed clear to light yellow to aid in leak detection.

• The hot dowtherm fluid from the reactor is sent to a waste heat recovery boiler to generate steam.

• The vapour stream is cooled using a integrated heat exchanger using the unreacted vapour stream generated from an absorber.

• The vapour stream is then sent to the heat integrated exchanger and is then sent back to the reactor and a fraction of that is purged to eliminate the accumulation of inerts such as Nitrogen and Argon.

• The product vapors are compressed and sent to a water absorber which absorbs ethylene oxide from the feed vapors. Eventually, the ethylene oxide rich water stream is sent to a stripper which desorbs the ethylene oxide + water as vapour and generates the regenerated water as bottom product. The regenerated water reaches the absorber through a heat integrated exchanger.

• The ethylene oxide + water vapour mixture is compressed (to about 4 - 5 atms) and then sent to a stripper to generate light ends + H₂O as a top product and the bottom product is then sent to another fractionators to produce ethylene oxide as top product. The heavy ends are obtained as bottom product.