In the past, the industrial production of Adipic acid used benzene as a
starting material. Benzene is one of the basic chemicals for industrial
reactions and a solvent. It is known that derives mainly from the refining
processes of the petrochemical industry. Be3nzene is also known for its
carcinogenic properties (it causes leukemia to highly exposed workers).
Afterwards the starting material became cyclohexanone or a mixture of
cyclohexanone and cyclohexanol. For the oxidation process it was used nitric
acid, producing toxic fumes of nitric oxides, NOx, which are also contributors
to the greenhouse effect and the destruction of the ozone layer in the
stratosphere. It was Inevitable that the method had to be changed again with
more environmentally benign reactions.