Synergistic Effect Enhancing Baeyer-Villiger Oxidation Performance of Resin-Derived-Carbon Supported FeCe Bimetallic Catalyst

Upgrading cyclohexanone to & epsilon;-caprolactone (& epsilon;-CL) is of great importance to the synthesis of high value-added downstream chemicals and the reduction of foam plastic. The catalytic synthesis of & epsilon;-CL from cyclohexanone through O2/aldehyde method is an environmentally benign one-pot tandem reaction without using peroxy acid, balancing the requirements of safety and efficiency. However, due to lack of elaborate design and collaboration of multiple active sites for catalysts, the catalytic efficiency of O2/aldehyde method still remains to be improved. Herein, a pitaya-like catalyst (CeFe@RDC-3) with Ce and Fe highly dispersed on resin-derived-carbon is synthesized through high temperature self-assembly. On this bimetallic catalyst, high yield (97 %) of & epsilon;-CL is achieved through aerobic oxidation of cyclohexanone with only 1.5 equivalent benzaldehyde. Moreover, considerable yields of & epsilon;-CL, 88.3 % and 74.7 %, respectively, are also obtained over CeFe@RDC-3 with green solvent (EtOAc) or even without solvent. No loss of activity is observed after five successive cycles, demonstrating high stability of CeFe@RDC-3. The mechanism study reveals that the high performance of CeFe@RDC-3 is ascribed to the Ce-Fe bimetallic synergy, uniform metal dispersion, abundant active oxygen and stabilizing effect of resin-derived-carbon to free radicals. This work provides prospect for a green, safe and low-cost strategy for Baeyer-Villiger process. Benefiting from the synergistic effect of supported bimetallic CeFe which induces higher metal dispersion and higher content of reactive oxygen, and the buffering effect of resin-derived-carbon on free radicals, the aerobic oxidation of cyclohexanone to & epsilon;-caprolactone (& epsilon;-CL) is performed over CeFe@RDC-x, and the catalytic efficiency is significantly improved. Especially, when solvent-free and green solvents (such as ethyl acetate) are used, excellent catalytic conversion effects are achieved.image