Ambient Synthesis of Cyclohexanone Oxime via In Situ Produced Hydrogen Peroxide over Cobalt-Based Electrocatalyst.

Abstract

Cyclohexanone oxime, a critical precursor for nylon-6 production, is traditionally synthesized via the hydroxylamine method under industrial harsh conditions. Here is present a one-step electrochemical integrated approach for the efficient production of cyclohexanone oxime under ambient conditions. This approach employed the coupling of in situ electro-synthesized H₂O₂ over a cobalt (Co)-based electrocatalyst with the titanium silicate-1 (TS-1) heterogeneous catalyst to achieve the cyclohexanone ammoximation process. The cathode electrocatalyst is consisted of atomically dispersed Co sites and small Co nanoparticles co-anchored on carboxylic multi-walled carbon nanotubes (CoSAs/SNPs-OCNTs), which delivered superior electrocatalytic activity toward the two-electron oxygen reduction reaction (2e^- ORR) with high-efficient H₂O₂ production in 0.1 m sodium phosphate (NaPi). Theoretical calculations revealed that the introduction of Co nanoparticles effectively optimized the binding strength of ^*OOH species on Co atomic sites, thus facilitating the 2e^- ORR. The subsequent tandem catalytic system achieved a high cyclohexanone conversion of 71.7% ± 1.1% with a cyclohexanone oxime selectivity of 70.3% ± 0.6%. In this system, the TS-1 catalyst effectively captured the ^*OOH intermediate and activated the in situ generated H₂O₂ to form Ti-OOH species, which promoted the formation of hydroxylamine and thereby enhanced the oxime production performance.