Study On Selective Oxidation Of 5-hydroxymethyl Furfural To 2,5-furandimaldehyde Under Visible Light

The development and utilization of green renewable energy into useful chemicals is one of the solutions to the shortage of fossil resources.5-Hydroxymethylfurfural（HMF）is an important intermediate for the synthesis of a variety of fine chemicals and furan-based polymers.It is considered to be a bridge connecting biomass resources and the petroleum industry.It can be formed by the degradation of biomass macromolecules through a simple and low-cost synthesis process.2,5-Furandiformaldehyde（DFF）,as one of the oxidation products of HMF,can be used in the synthesis of drugs,functional polymers,and bactericides.The selective oxidation of HMF into DFF with high efficiency has attracted much attention.The current catalytic system has some problems such as high energy consumption and unfriendly environment,so a low-cost,eco-friendly photocatalytic process is undoubtedly a more suitable choice.In this paper,two composite catalysts have been developed and used in the visible light catalytic oxidation of 5-hydroxymethylfurfural to 2,5-furandiformaldehyde.1.The Bi₂WO₆/mpg-C₃N₄ composite catalyst was prepared by hydrothermal method.The structure and composition of the photocatalyst were characterized by XRD,SEM,UV-Vis,FT-IR and XPS.The optical and electrochemical properties were studied by EIS,PC and PL.Through the capture experiment of active species,it can be inferred that·O₂^-is the main active species during reaction process.The formation of the heterostructure between Bi₂WO₆ and mpg-C₃N₄ can effectively transfer electrons and holes,inhibit photo-generated electron-hole recombination and improve the photocatalytic reaction performance.Under visible light irradiation,over the Bi₂WO₆/mpg-C₃N₄ photocatalyst the HMF conversion rate of 59.3%is obtained with DFF selectivity of 84.3%.2.The CdIn₂S₄/mpg-C₃N₄ composite photocatalyst was prepared by a simple precipitation method.The structure and composition of CdIn₂S₄/mpg-C₃N₄photocatalyst were studied by XRD,SEM,UV-Vis,FT-IR and XPS,etc.The optical and composition of CdIn₂S₄/mpg-C₃N₄ photocatalyst were analyzed by EIS,PC and PL.The effects of different reaction conditions on the catalytic performance were investigated,and the optimal reaction conditions were determined.The reactive species were explored through quencher experiments.The formation of the heterostructure of the CdIn₂S₄/mpg-C₃N₄ composite catalyst reduces the photo-generated electron-hole recombination efficiency and improves the photocatalytic reaction performance.Under visible light irradiation,the highest HMF conversion rate of 52%on the CdIn₂S₄/mpg-C₃N₄ photocatalyst is obtained,with the DFF selectivity of 81%.