Page 89 - Chemical and process design handbook

Speight_Part II_A 11/7/01 3:16 PM Page 2.30

ADIPIC ACID

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Adipic acid (melting point: 152.1 C, density: 1.344) is manufactured pre-
dominantly by the oxidation of cyclohexane followed by oxidation of the
cyclohexanol/cyclohexanone mixture with nitric acid (Figs. 1 and 2):
C H → CH CH CH CH CH CHOH + CH CH CH CH CH C=O
6 12 2 2 2 2 2 2 2 2 2 2
CH CH CH CH CH CHOH + [O] → HO C(CH ) CO H
2 2 2 2 2 2 2 4 2
CH CH CH CH CH C=O +[O] → HO C(CH ) CO H
2 2 2 2 2 2 2 4 2
There is no need to separate the cyclohexanol/cyclohexanone mixture into
its individual components; oxidation of the mixture is carried out directly.
Adipic acid can also be made by hydrogenation of phenol with a palla-
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dium or nickel catalyst (150 C, 50 psi) to the mixed oil, then nitric acid
oxidation to adipic acid. If palladium is used, more cyclohexanone is
formed.

Recycle
Catalyst
Recycle
Cyclohexane

Caustic
Air
Salt solution

Acid-alcohol-ketone
mixture
FIGURE 1 Manufacture of adipic acid by aerial oxidation of cyclohexane.

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