Study On The Selective Oxidation Of 5-hydroxymethylfurfural To 2,5-furandicarboxylicacid Over Supported Gold And Palladium Bimetallic Catalysts

Utilizing the carbon neutrality and high oxygen content of biomass,developing biomass directed conversion to produce high-value oxygen-containing chemicals of biomass is an important way to replace petrochemical products with biomass,which is of great significance for the sustainable development strategy of energy.2,5-furandicarboxylicacid（FDCA）is the most potential substitute of petroleum terephthalic acid（PTA）,which has a wide range of application prospects in plastics,packaging and other fields.5-Hydroxymethylfurfural（HMF）can be obtained from a wide range of sources of inexpensive biological carbohydrates,using it as the raw material to prepare FDCA is more in line with the concept of environmentally friendly,green and sustainable development.Supported noble metal catalysts often show high catalytic activity,and the choice of support is the key to the activity and stability of catalyst.In this work,a series of supported noble metal catalysts were prepared for catalytic oxidation of HMF to prepare FDCA.Firstly,hollow rod-shaped nitrogen-doped carbon-supported AuPd bimetallic catalysts were prepared using halloysite（HNTs）as template,which realized the oxidation of HMF to prepare FDCA in basic solvent.Secondly,nanoreactor catalysts were prepared using porous carbon coated AuPd alloy,which realized the efficient oxidation of HMF to prepare FDCA,showing excellent selectivity and stability.Finally,sepiolite supported AuPd bimetallic catalysts with alkaline functional groups on the surface were prepared to realize the base-free oxidation of HMF to prepare FDCA.The specific research results are as follows:（1）Hollow rod-shaped nitrogen-doped carbon-supported AuPd bimetallic catalyzed oxidation of HMF to prepare FDCADue to the advantages of large specific surface area,rich pore structure,excellent adsorption performance and surface modification,porous carbon materials are used as ideal supports for various catalysts.In this study,the natural clay ore halloysite,which is cheap in nature,abundant in yield,stable in performance and friendly to environment,was used as the template.After precipitation polymerization,high-temperature carbonization and template removal,porous carbon carrier was obtained.Then the hollow rod-like nitrogen-doped carbon-supported AuPd bimetallic catalyst was prepared by sol-gel method by loading Au and Pd nanoparticles on the surface.A series of catalysts with different nitrogen content and different metal sizes were prepared by adjusting the polymer monomer ratio and metal molar ratio.The oxidation of HMF to prepare FDCA was realized by the synergistic action between nitrogen doped carbon carrier and bimetal.The results showed that the 99.9%FDCA yield was obtained under the optimum conditions of aerobic oxidation of HMF with Au₃Pd₁/HRN₅C catalyst,which FDCA productivity could reach 17.9 mmol·g^-1·h^-1.（2）Porous carbon-coated AuPd alloy rod nanoreactor catalyzed HMF oxidation to FDCAIt is an effective means to promote the contact between reactants and active sites,and to improve the activity and stability of catalyst by coating AuPd nanoparticles in porous carbon carrier and providing microenvironment by designing micro-nano reactors.In this study,HNTs were used as the template,and AuPd nanoparticles were loaded onto HNTs by electrostatic attraction and in-situ reduction.Then,a layer of polymer was coated on the surface of the HNTs by precipitation polymerization.After pyrolysis and removal of the internal HNTS template,porous carbon-coated AuPd alloy rod nanoreactor catalyst was obtained.The confinement effect of the nanoreactor and the synergistic catalysis of AuPd alloy were used to achieve efficient oxidation of HMF to prepare FDCA.The results showed that the 99.9%FDCA yield could be obtained by aerobic oxidation of HMF with Au₂Pd₁@C₈₀₀ nanoreactor catalyst under the optimal reaction conditions,and there was no obvious activity loss after 12 cycles,showing excellent catalytic stability.In addition,the catalyst could also obtain 99.8%yield of FDCA for 30 minutes under the reaction of 1.0 wt%noble metal loading,which FDCA productivity could reach 2003.6 mmol·g^-1·h^-1,showing excellent catalytic performance.（3）Sepiolite supported AuPd bimetallic catalyzed base-free oxidation of HMF to prepare FDCASelective oxidation of HMF to prepare FDCA under base-free conditions is a major challenge in the field of green chemistry,and it also avoids problems such as equipment corrosion and product separation.In this study,natural alkaline sepiolite was used as the carrier to support Au and Pd nanoparticles,which provided more reaction sites for the supported catalyst due to its high porosity and rich surface hydroxyl groups,and the abundant surface hydroxyl group enabled the catalyst to prepare FDCA by efficient aerobic oxidation of HMF under base-free conditions.A series of supported catalysts were prepared by adjusting the ratio of AuPd bimetal.The results showed that under the optimal reaction conditions,the Au_1.2Pd₁/sepiolite catalyst could obtain 98.4%yield of FDCA for 10 h under base-free condition,which FDCA productivity could reach 41.5 mmol·g^-1·h^-1.