The Study On Preparation Of Au/Ce-Zr-O Catalyst And Their Catalytic Performances In The Oxidation Of 5-hydroxymethyl Furfural(HMF)

5-Hydroxymethylfurfural?HMF?is an important biomass platform molecule in which hydroxyl and aldehyde groups are present and can be selectively oxidized to2,5-furandicarboxylic acid?FDCA?.FDCA can theoretically be used as a substitute for petrochemical raw materials to synthesize polyester products and was therefore listed by the U.S.Department of Energy in 12 high value-added biomass-based compounds in 2004.In this paper,Au/Ce-Zr-O catalysts were prepared and characterized.The properties of catalytic oxidation of HMF were studied,and the relationship between catalyst structure and catalytic performance was explored.1,CeO₂,ZrO₂ and Ce_XZr_1-XO₂?X=0.5-0.9?composite oxides were prepared by the citric acid complex method,and 1wt%Au active component was loaded on the surface as a catalyst by deposition-precipitation method.The effect of Zr adulterates loading and the pH of the supported gold on the activity of the prepared catalyst.The structure,morphology and surface element states of the as-prepared catalysts were characterized by XRD,XPS,TEM and H₂-TPR.The study found that cerium oxide is mainly cubic fluorite crystal CeO₂,zirconia is mainly cubic crystal ZrO₂,Ce_XZr_1-XO₂ composite oxide,Zr content is less stable when the homogeneous cubic fluorite crystal CeO₂ crystal,the elements played a role in the adhesion of CeO₂ particles,CeO₂ and ZrO₂ crystals were present when the content of Zr was large.The gold active component exhibits the morphology of nanoparticles,the gold particles supported on a single oxide exhibit a regular spherical distribution,and the gold particles supported on the composite oxide exhibit an irregular spherical distribution around the periphery which thereby increasing the contact between the gold particles and the carrier.The surface of Au/Ce-Zr-O catalyst is mainly Au⁰,Ce⁴⁺and Zr⁴⁺,and Au?1wt%?/Ce_0.9Zr_0.1O₂?the pH of the loaded gold is 5.92?catalyst has strong interaction between gold particles and support whom contains a small amount of Ce³⁺as well as a large number of oxygen vacancies and adsorbed oxygen species.2.Establish a standard curve by HPLC and calculate the conversion of HMF and the selectivity of the product using external standard method.Using water as a solvent,sodium hydroxide was added,and oxygen was used as an oxidant to oxidize the HMF reaction with the above catalyst.It was found that Au?1 wt%?/Ce_0.9Zr_0.1O₂ catalyst can efficiently oxidize HMF to FDCA when the pH value is 5.92.When the temperature was 90°C,the reaction time was 3 h,and the oxygen pressure was 1 MPa,the conversion of HMF was100%,and the selectivity of FDCA was 97.3%.It was found that during the conversion of HMF to FDCA,the oxidation of hydroxy groups to aldehydes is the rate-determining step in the entire catalytic process.A small amount of Zr doping can speed up the electron transfer rate,A small amount of Zr doping can speed up the electron transfer rate,and at a suitable pH value,there is a strong interaction between the supported gold particles and the carrier,resulting in a small amount of Ce³⁺ions on the surface of the carrier,thereby improving the adsorption of the catalyst surface.The content of oxygen and oxygen vacancies helps to accelerate the oxidation rate of hydroxyl groups to aldehyde groups,thereby increasing the selectivity of FDCA.