ABSTRACT
Adipic acid is the most important aliphatic carboxylic acid because of its use as an intermediate in the production of nylon 66. The advantages of the nitric acid process over the air oxidation processes are: good yield; high conversion rate; short reaction time; and high product purity, suitable for nylon 66. Hydrocarboxylation processes for the synthesis of adipic acid have been patented by BASF and Texaco. Over 94% of adipic acid is manufactured from cyclohexane, with the remainder employing cyclohexanol or phenol as the starting material. Water contained in the reaction mixture is flashed off under vacuum distillation and adipic acid is recovered from the concentrated product stream by crystallization at 5°C, followed by centrifuging. Most production of adipic acid is used captively by the major fibre manufacturers. Care must be taken when handling adipic acid to avoid exposure to dust which can cause irritation to skin, nose and throat.
