In the industry large-scale chemical processes have been established
to produce adipic acid (Merchant Research & Consulting Ltd.,
2011). Almost all of the commercial adipic acid is obtained from
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E-mail address: t.polen@fz-juelich.de (T. Polen).
benzene, which is first reduced to cyclohexane. Cyclohexane is then
converted to a mixture of cyclohexanone and cyclohexanol by two
successive oxidation steps. This mixture is further reacted to adipic
acid with nitric acid and air using copper or vanadium as catalyst
(Fig. 1). Adipic acid is also made by the hydrocyanation of butadiene,
followed by hydroisomerization to adiponitrile, which then is
hydrolyzed. These and further chemical synthesis routes to adipic
acid have been reviewed, e.g. by Musser (2005).