Study On Catalytic Oxidation Of Bio-derived 5-Hydroxymethylfurfural Into 2,5-Diformylfuran Over Vanadium-based Catalysts

In recent decades,biomass resources are considered as the only renewable resources to replace fossil resources for the production of chemicals and liquid fuels.Therefore the conversion of biomass derived carbohydrates into 5-hydroxymethylfural?HMF?and 2,5-diformylfuran?DFF?has attracted much more attention in the scientific and industrial communities.According to the current research situation and exiting problems in HMF and DFF production,a series of studies persisted in the concept of green chemistry were carried out in this dissertation.This work describes on the aerobic oxidation of bio-derived HMF,which mainly focuses on the synthesis of green,efficient,low-cost and easily recycled catalysts.In this thesis,much work was focused on the catalytic conversion of HMF to DFF over magnetic core-shell nanoparticles Fe₃O₄@SiO₂-NH₂-VO²⁺ and Fe₃O₄@SiO₂-NH₂-Cu²⁺ catalysts.Amino functional Fe₃O₄@SiO₂ was used to immobilize Cu²⁺ and VO²⁺ for preparing Fe₃O₄@SiO₂-NH₂-Cu²⁺ and Fe₃O₄@SiO₂-NH2-VO²⁺ catalysts.Various technologies had been developed for the characterization of catalysts,such as XRD,XPS,FT-IR,SEM,TEM and VSM.The catalytic activity of Fe₃O₄@SiO₂-NH₂-VO²⁺ in HMF oxidation could be significantly enhanced by the use of Fe₃O₄@SiO₂-NH₂-Cu²⁺ as the co-catalysts.Moreover,the co-catalysts exhibited great stability and can be easily separated from mixture for the next run.As a comparison with other catalysts supports to improve the BET surface of the catalysts,the catalytic effect of amino functional mesoporous sieve MCM-41 was prepared for the oxidation conversion of HMF into DFF.Amino modified MCM-41?MCM-NH₂?was used to graft VO²⁺ and cupric Cu²⁺ ions,giving MCM-NH₂-VO²⁺ and MCM-NH₂-Cu²⁺ catalysts,respectively.Excellent activity and great stability were obtained with VO²⁺ or Cu²⁺ supported amino-functionalized MCM-41 in comparison with that of two ions supported mesoporous silica.In addition,V₂O₅/SBA-15 catalysts with theoretical loadings of 5,10,15 and 20%?by weight?V₂O₅ were prepared by the Molecular Designed Dispersion?MDD?method and characterized by various methods such as N₂-physisorption,low-angle and wide-angle XRD,TEM,FT-Raman,DRS and ICP-OES.Particularly,the 10%V₂O₅/SBA-15 catalyst showed highest HMF conversion and DFF selectivity in the presence of molecular oxygen under mild condition.The appreciable performance of the 10%V₂O₅/SBA-15 catalyst can be probably attributed to the isolated distribution of nano-vanadium species on the pore surfaces of hexagonally ordered mesoporous SBA-15.In conclusion,the results of characteristics suggested that VO²⁺ could be oxidized in the presence of Cu²⁺,and V^V species was obtained under the reaction conditions,which indicates that a V^IV/V^V redox cycle is probably involved.This study has provided a low-cost process and a certain industrial prospect for the oxidation of HMF into DFF.