Aerobic Cyclohexane Oxidation Catalyzed by Vanadium‐Substituted LaCoO3 Perovskites in the Liquid Phase

Abstract Spray flame‐synthesized LaV x Co 1‐x O 3 perovskites (x = 0.00, 0.01, 0.03, 0.05, 0.3, and 0.5) were found to enhance the KA oil (mixture of cyclohexanol and cyclohexanone) selectivity in the aerobic liquid‐phase oxidation of cyclohexane. The KA oil selectivity significantly improved even for a low vanadium doping of x = 0.01, and for x = 0.03, conversion and KA oil yield reached 22.5% and 17.1%, respectively, under mild reaction conditions of 120 °C and 15 bar O 2 . Kinetic investigations performed over LaV 0.03 Co 0.97 O 3 exhibited a first‐order‐like reaction with a low apparent activation energy of 44.8 kJ mol −1 , which is ascribed to the Co 2+ fraction generated upon doping V, which decomposes the cyclohexyl hydroperoxide (CHHP) intermediate. Radical scavenging studies combined with the electron paramagnetic resonance (EPR) spin trap studies identified C 6 H 11 OO ● , C 6 H 11 O ● , HO ● , O 2 •− , and C 6 H 11 ● as the active free radicals. Post‐reaction characterization revealed the partial reduction of Co 3+ to Co 2+ and presumably of V 5+ to V 4+ during cyclohexane oxidation. A plausible catalytic cycle is proposed based on an initial proton‐coupled electron transfer (PCET) process where the higher‐valent cations, such as Co 3+ and V 5+ , are reduced to lower‐valent Co 2+ and V 4+ , which further participate in a Haber–Weiss cycle, decomposing the CHHP intermediate.