Preparation of adipic acid by oxidation of cyclohexanol and cyclohexanone with nitric acid: Part I. Reaction mechanism

✍ Scribed by W. J. van Asselt; D. W. van Krevelen

• Publisher: Elsevier Science
• Year: 2010
• Tongue: English
• Weight: 662 KB
• Volume: 82
• Category: Article
• ISSN: 0165-0513
• DOI: 10.1002/recl.19630820107

✦ Synopsis

Abstract

The oxidation of cyclohexanol with nitric acid to adipic acid proceeds via two stable intermediates known from the literature^1^ viz. 6‐hydroxyimino‐6‐nitro hexanoic acid and the hemihydrate of 1,2‐cyclohexanedione, two substances forming beside each other in a given ratio. This ratio can be calculated as a function, of the temperature and of the nitric acid and nitrous acid concentrations. The nitrous acid plays a very important part in the oxidation process. The oxidation of cyclohexanone proceeds in the same way as that of cyclohexanol, provided sufficient nitrous acid is present. In the absence of HNO~2~ the oxidation does not proceed at all at low temperatures.

The catalysts used ‐ ammonium vanadate and copper nitrate ‐ have very different functions. Under the influence of the vanadate the hemihydrate of cyclohexanedione is rapidly converted to adipic acid, whereas in the absence of vanadate this substance is slowly broken down to glutaric acid, succinic acid and oxalic acid. Copper is effective only at higher temperatures where it prevents the further break‐down of unstable intermediates.