Producing adipic acid without the nitrous oxide

Synthesis of nylon monomer from butadiene avoids emission of a potent greenhouse gas Adipic acid is a monomer for nylon polymers such as polyamide 66. As of now, its production by the oxidation of a cyclohexanone–cyclohexanol mixture with nitric acid (1) (see the figure) on an annual scale of multimillions of metric tons also produces stoichiometric amounts of the potent greenhouse gas nitrous oxide (N2O). The double carbonylation of butadiene to adipic acid or its esters could be a viable alternative that would avoid the use of nitric acid and emission of N2O and would also have a more flexible raw-material base. Several systems for this reaction have been reported in the past decades, mainly from commercial labs, but none have been developed as an industrial process because of insufficient activity, selectivity, or both (1, 2). On page 1514 of this issue, Yang et al. (3) now report a single-step system for the double carbonylation of butadiene with previously unmatched activity and selectivity.