Synthesis Of Graphene/Metal Nanomaterials And Investigation On Catalytic Oxidation Performance

In industrial production,heterogeneous catalysts can be easily separated from the reaction system and used circularly,which greatly overcomes the defect of homogeneous catalysts.However,low activity has brought challenges to the practical application of heterogenous catalysts in industrial catalysis.In order to solve the problem concerning low activity of heterogeneous catalysts,graphene,a new two-dimensional carbon material with excellent electrical properties,thermal stability and large specific surface area,is used as a carrier for loading metal nanoparticles.In this work,two kinds of graphene-based nano metal heterogeneous catalysts were designed and synthesized.They exhibited the characteristics of high efficiency and recycling in the catalytic oxidation of benzyl alcohol and ethylbenzene respectively.The main experimental contents and results are as follows:1.Reduced graphene oxide supporting copper nanoparticles（Cu/rGO）catalyst was obtained by one-step reduction method with NaBH₄.The surface morphology and chemical composition of the catalyst were analyzed by XRD,TEM,SEM and XPS.The catalytic performance of the Cu/rGO catalyst was evaluated by selective oxidation of benzyl alcohol in H₂O with O₂ and TEMPO.With optimizing the reaction conditions,it was found that Cu/rGO catalyst gave the 97%benzyl alcohol conversion and 99%benzaldehyde selectivity when the reaction temperature was 80℃,the reaction time was 10 h and the amount of catalyst was 16mg.Cu/rGO was reused for five times under optimized conditions and the conversion of benzyl alcohol and the selectivity of benzaldehyde were not found to be decreased significantly,indicating that the Cu/rGO catalyst had good cycling ability.The reaction system is suitable for the catalytic oxidation of various aromatic alcohols.2.Co₃O₄ nanoparticles evenly dispersed on the surface of reduced graphene oxide（Co₃O₄/rGO）were synthesized by hydrothermal method.The XRD,TEM,SEM and XPS were operated to characterize the structure of the Co₃O₄/rGO catalyst.The catalytic performance of the Co₃O₄/rGO catalysts was evaluated by selective oxidation of ethylbenzene in CH₃CN with O₂ and NHPI.The experimental results showed that 84%ethylbenzene conversion and 96%acetophenone selectivity were achieved within 2 h under 120℃.Co₃O₄/rGO was reused for five times under optimized conditions and the conversion of ethylbenzene and the selectivity of acetophenone were not found to be decreased significantly,indicating that the Co₃O₄/rGO catalyst had good cycling ability.The reaction time was greatly shortened in this reaction system,thus the amount of by-products was reduced and the selectivity of acetophenone was improved.The experimental results show that graphene as support material can improve the catalytic activity of metal nanomaterials,which provide a strategy for preparing other metal/graphene heterogeneous catalysts with high catalytic activity.