Ethylbenzene is converted to styrene in the catalytic dehydrogenation reaction A flowchart of a simplified version of
Question:
Ethylbenzene is converted to styrene in the catalytic dehydrogenation reaction
A flowchart of a simplified version of the commercial process is shown here.
Fresh and recycled liquid ethylbenzene combine and are heated from 25°C to 500°C Ⓐ, and the heated ethylbenzene is mixed adiabatically with steam at 700°C Ⓑ to produce the feed to the reactor at 600°C. (The steam suppresses undesired side reactions and removes carbon deposited on the catalyst surface.) A once-through conversion of 35% is achieved in the reactor Ⓒ, and the products emerge at 560°C. The product stream is cooled to 25°C Ⓓ, condensing essentially all of the water, ethylbenzene, and styrene and allowing hydrogen to pass out as a recoverable by product of the process.
The water and hydrocarbon liquids are immiscible and are separated in a settling tank decanter Ⓔ. The water is vaporized and heated Ⓕ to produce the steam that mixes with the ethylbenzene feed to the reactor. The hydrocarbon stream leaving the decanter is fed to a distillation tower Ⓖ (actually, a series of towers), which separates the mixture into essentially pure styrene and ethylbenzene, each at 25°C after cooling and condensation steps have been carried out. The ethylbenzene is recycled to the reactor preheater, and the styrene is taken off as a product.
(a) On a basis of 100 kg/h styrene produced, calculate the required fresh ethylbenzene feed rate, the flow rate of recycled ethylbenzene, and the circulation rate of water, all in mol/h. (Assume P = 1 atm.)
(b) Calculate the required rates of heat input or withdrawal in kJ/h for the ethylbenzene preheater Ⓐ, steam generator Ⓕ, and reactor Ⓒ.
(c) Suggest possible ways to improve the energy economy of this process.
Physical Property Data
Step by Step Answer:
Elementary Principles of Chemical Processes
ISBN: 978-1119498759
4th edition
Authors: Richard M. Felder, Ronald W. Rousseau, Lisa G. Bullard