Mechanism of Synergistic Ce–Mn Catalysis for One-Step Highly Selective Cyclohexane Oxidation to KA-Oil

The one-step oxidation of cyclohexane to KA-oil (a critical intermediate for ε-caprolactam and adipic acid synthesis) represents a formidable catalytic challenge. Herein, the highly stable Ce–Mn composite oxide (CeMnOx) catalyst was prepared via the sol–gel method. Under optimal conditions, 7.7% cyclohexane conversion with 85.6% selectivity to KA-oil was acquired. Remarkably, CeMnOx retained its initial activity and structural integrity over 10 catalytic cycles. Comprehensive characterization revealed that the coexistence of multivalent Mn (Mn3+/Mn2+) and Ce (Ce4+/Ce3+) species enables synergistic redox interplay. This synergy critically directs the efficient decomposition/reduction of the cyclohexyl hydroperoxide (CHHP) intermediate, thereby enhancing the KA-oil yield. Integrated in situ DRIFTS studies and density functional theory calculations elucidated a radical-mediated reaction mechanism underpinned by the synergistic Ce–Mn couples. This work not only demonstrates a viable strategy for efficient single-step KA-oil production but also provides fundamental insights into designing selective oxidation catalysts for alkanes.