Preparation of acetic acid: (the second method)

Vinegar fermenting:

A classical way to prepare acetic acid is fermenting (i.e, oxidize ethylic alcohol by air with the presence of vinegar ferment):

CH₃ – CH₂ – OH + O₂ ® CH₃ – COOH + H₂O

The condition for fermenting is that the concentration of alcohol is less than 10 degree. Besides, alcohol and vinegar ferment are contacted with a large amount of air.

Preparation of acetic acid: (the first method)

Synthesizing from C₂H₂ (acetylene):

-         One modern method for preparation of acetic acid is synthesizing from acetylene. Let acetylene do addition reaction with water with HgSO₄ or HgCl₂ as reactive catalyst to form acetaldehyde:

CH º CH + H₂0 ® CH₃ – CH = O (with HgSO₄ or HgCl₂ at 80^oC)

-         Oxidize CH₃CHO by O₂ in air with salt (CH₃COO)₂Mn as a catalyst:

2CH₃ – CH = O + O₂ ® 2CH₃ – COOH

This synthesizing process is done by several steps as following:

-         Water addition tower: Let acetylene and the catalyst solution with high temperature (at about 80^oC) flow into a water addition tower in the direction from the bottom to the top.

Acetaldehyde will be formed at this tower.

-         Washing tower: Acetaldehyde formed with acetylene are connected to the bottom of the washing tower. The air mixture goes from the bottom to the top of the washing tower, while water is going from the top to the bottom by opposite direction rule.

Acetylene not dissolved in water will be sublimated and then recovered. Acetaldehyde is dissolved in water to form a solution.

-         Distilling tower: Acetaldehyde solution is brought to the distilling tower to separate acetaldehyde from water.

-         Oxidizing tower: Bring acetic acetaldehyde vapor and O₂ (or air) to the oxidizing tower in the direction from the bottom to the top. The catalyst (CH₃COO)₂Mn solution flows from the top by the opposite direction rule. At this tower, acetaldehyde will be oxidized to become acetic acid. Separate acid from catalyst by distilling and refining method to get acetic acid.