Synergistic NiCu Alloy Catalysis for the Sustainable Upcycling of N -Cyclohexylcyclohexanamine to Cyclohexylamine via Reductive Amination

The oxidative conversion of cyclohexylamine (CHA) is a sustainable route to cyclohexanone oxime, but its main byproduct, N-cyclohexylcyclohexanamine (N-CCA), largely diminishes the atom economy. Herein, an innovative strategy for the upcycling of N-CCA back to CHA using a non-noble bimetallic NiCu/MgAlO catalyst via reductive amination has been reported. The catalyst, synthesized by urea-assisted coprecipitation, achieved 99.8% N-CCA conversion with 99.6% CHA selectivity under mild conditions using ethanol as a green solvent. The process exhibits 99.4% atom utilization and outstanding catalytic stability. Critically, a quantitative green metrics analysis reveals remarkably low waste generation, with an reaction E-factor of 3.62 and a process mass intensity of 4.62, underpinning the sustainability of this waste-to-value strategy. Density functional theory calculations revealed that the reaction proceeds mainly through a hydrogenation-first pathway (with H2) followed by amination (with NH3). Compared to the Ni(111) and Cu(111), the NiCu(111) facet exhibited stronger adsorption-activation capability for N-CCA and a lower activation energy for the rate-determining step. This work provides a green and practical solution for enhancing the circularity of nylon-6 production.