The production of adipic acid (a precursor for nylon-6,6) via nitric acid oxidation of cyclohexane/cyclohexanol generates significant quantities of N₂O as a byproduct. This single industrial process historically contributed approximately 5–8% of global anthropogenic N₂O emissions.
The Reaction
In adipic acid synthesis, cyclohexanol and cyclohexanone (“KA oil”) are oxidized with nitric acid at 60–80°C in the presence of copper and vanadium catalysts. The reaction sequence produces N₂O as an undesirable byproduct alongside the target adipic acid.
Abatement Technologies
Since the late 1990s, major adipic acid producers have implemented thermal decomposition and catalytic reduction systems that destroy over 98% of generated N₂O. BASF, Invista, and Radici Group have all deployed high-temperature (850–1000°C) thermal oxidation units with secondary heat recovery.