Acetaldehyde Flowsheet

Topics: Oxygen, Ethanol, Nitrogen Pages: 3 (819 words) Published: December 11, 2012
Process Description
Acetaldehyde is produced via dehydrogenation of Ethanol. The reaction is as below: CH3CH2OH CH3CHO + H2 , ΔH = +82.5 kJ/mol

Besides the main reaction producing Acetaldehyde, there are three side reactions present in the reactor, as shown below: 2 CH3CH2OH CH3COOC2H5 + H2
2 CH3CH2OH CH3(CH2)3OH + H2O

The feed of 90% Ethanol is kept in a storage tank with an air vent. Tank blanketing is used in the storage tank with Nitrogen gas. This is to prevent contamination of the feed. Nitrogen tank blanketing will reduce the oxygen level in the tank, and thus reduce the risk of fires and/or explosions posed by Ethanol, which is a volatile and combustible substance. The Nitrogen gas will exit from the air vent, preventing it from flowing into the process.

The feed is pumped from a pressure of 1 bar to 6 bar, and is then mixed with the recycle stream of 90 % Ethanol composition. The reason of operating the process at high pressure is to ensure maximum separation of product, by-products and unreacted Ethanol after the reactor. The mixture is pre-heated to a temperature of 275oC (the optimum temperature for dehydrogenation of Ethanol using Copper-Chromium-Cobalt catalyst) before entering the packed bed reactor. The reaction takes place in gaseous state. The reason for using a packed bed reactor is because it allows gaseous reactions, has higher conversion per weight of catalyst compared to other catalytic reactors and the reaction rate is dependent on the catalyst surface area instead of the volume of reactor, allowing it to take up less space without affecting the rate of reaction.

In the reactor, the catalyst used is Copper, with small traces of Chromium and Cobalt. The selection of catalyst was chosen because of its ability to sustain an average of approximately 90% activity for up to 100 hours. The conversion of Ethanol is assumed to be 50% and the yield of Acetaldehyde is assumed to be 85%. Among...
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