Adipic Acid (98/99-3)
Currently operating commercial production processes for adipic acid depend on the production or purchase of KA oil (a mixture of cyclohexanone, the ketone or K component, and cyclohexanol, the alcohol or A component), or of pure cyclohexanol, and its subsequent oxidation in solution to adipic acid using an excess of strong nitric acid. This report deals with KA oil/cyclohexanol production by various routes, followed by the common step of nitric acid oxidation. KA oil production from cyclohexane by the cobalt catalyst and boric acid air oxidation routes is reviewed. Production of KA oil from phenol is also covered, as is the Asahi process for cyclohexanol production from benzene via cyclohexene. Appropriately adjusted nitric acid oxidation is appended to each of these processes.
Solutia, working with the Boreskov Institute of Catalysis (BIC) in Russia, has developed a one step process to manufacture phenol from benzene, using nitrous oxide for the oxidation step. Thus, by coupling phenol production and adipic acid production, Solutia has no net production of nitrous oxide and very good production economics for both phenol and adipic acid.
In addition to the commercially employed technologies that all go through cyclohexanone or cyclohexenol or mixtures of both (KA oil), several speculative direct synthetic routes are covered in this report. These routes include butadiene-based processes, acrylic acid dimerization and direct oxidation of cyclohexane with oxygen of hydrogen peroxide. The chemistry of the commercial and speculative routes of adipic acid are summarized below.
O2 or H2O2