Preparation Of CoCe Binary Oxide Nano-junctions And Its Catalytic Oxidation Of 5-hydroxymethylfurfural

Making full use of renewable biomass resources becomes an effective way of al eviating the energy crisis.General y,2,5-furandicarboxylic acid（FDCA）has played a key role in the material monomers,pharmaceutical intermediates,and fuels.So,the FDCA transformed from a bio-based platform substance of 5-hydroxymethylfurfural（HMF）understandably has received significant attention in recent years.However,there is a chal enge for the efficient oxidation of HMF to FDCA.Considering the high cost of noble metal catalysts and the lower activity of single component non-noble metals,the CoCe binary oxide nanojunctions were designed for the HMF oxidation to FDCA in this work.The main conclusions of this work were shown as follows:（1）A series of CoCe binary oxide nanojunctions catalysts with various CoCe molar ratios were prepared by the citric acid sol-gel method.Then the as-prepared samples were characterized by ICP-OES,XRD,N₂ isotherms,TEM,HRTEM,EDS-Mapping,XPS,O₂-TPD and EPR.And the HMF oxidations were performed over the as-prepared samples.Based on the results of characterization and reactions,we found that CoCe-15 with a CoCe molar ratio of 15 displayed excellent catalytic performance.Then,the effects of reaction conditions（reaction temperature,alkaline,reaction time,and pressure）on the HMF oxidation were also investigated on the catalyst of CoCe-15.The results showed that the conversion of HMF was 100%while the yield of FDCA at 77.4%for 4 h and 84.4%for 8h under the reaction conditions of 130℃,0.6 MPa O₂,and a lower concentration of aqueous sodium hydroxide solution.It was also found that the interfaces in the nanojunctions played a crucial role in HMF oxidation.In addition,the results of EPR analyses showed that superoxide anion（·O₂^-）was involved in the oxidation reaction.（2）For further to study the role of the interfaces in HMF oxidation,we prepared a series of CoCe binary oxide nanojunctions by using the different complexing agents of malic acid,lactic acid,acetic acid and water instead of citric acid.Then the as-prepared samples were also characterized by ICP-OES,XRD,N₂ isotherms,TEM,HRTEM,EDS-Mapping,XPS,O₂-TPD and EPR.The results suggested that the types of complexing agents strongly influenced on the formation of the nanojunctions,which displayed a key role in the HMF oxidation.Based on the results of characterization and reactions,the MA-CoCe,which was prepared using malic acid,had the richest interfaces and understandab ly displayed the best catalytic activity in HMF oxidation.The results showed that the conversion of HMF was 100%while the yield of FDCA at 83.9%for 4 h under the reaction conditions of 130℃,0.6 MPa O₂,and a lower concentration of aqueous sodium hydroxide solution,While the yield of FDCA was 92.3%at 110℃for 15 h.Additionally,the temperature of 110℃might be the optimum reaction temperature which could balance the FDCA selectivity and the reaction rate.