Question

Acetaldehyde is a colorless liquid with a pungent, fruity odor. It is primarily used as a chemical intermediate, principally for the production of acetic acid, pyridine and pyridine bases, peracetic acid, pentaeythritol, butylene glycol, and chloral. Acetaldehyde is a volatile and flammable liquid that is miscible in water, alcohol, ether, benzene, gasoline, and other common organic solvents. In this problem, the synthesis of acetaldehyde via the dehydrogenation of ethanol is to be considered. The following reactions occur during the dehydrogenation of ethanol:

 

The single-pass conversion of ethanol is typically 60%. The yields for each reaction are approximately:

1. Acetaldehyde 92%

2. Ethyl acetate 4%

3. Butanol 2%

4. Acetic acid 2%

1. For this process, generate a process concept diagram showing all the input and output chemicals.

2. Develop two alternative preliminary process flow diagrams for this process.

Answer 1

a.

 

Order of volatility is acetaldehyde, water, ethyl acetate, ethanol, isobutanol, acetic acid.

 b.

 

Alternative 1 assumes butanol and acetic acid can be sold as a mixed product ⇒ very unlikely so probably have to add another column to separate. 

This alternative recycles C2H5OH and produces “pure” acetaldehyde the remaining streams are considered waste incineration of organics or wastewater treatment are possible ways to remove organics.