The Preparation Of Solid Polyoxometalates Catalysts In Catalytic Oxidation Of 5-HMF

With the increasing demand for renewable and sustainable energy sources,the replacement of petroleumbased carbon sources for synthesizing chemicals and materials have become important.Even though increasing attention has been devoted to renewable energy resources like solar,wind,and geothermal,none of these renewable energies is able to produce organic chemicals.Biomass is the only renewable green carbon source.Among the biomass-derived intermediates for bio-refineries,5-hydroxymethylfurfural?5-HMF?is regarded as the most important precursor chemical for the production of plastics,liquid fuels and pharmaceuticals.In this regard,DFF is an important product of 5-HMF oxidation and can be used in the synthesis of organic conductors,poly?schiff bases?,pharmaceuticals,antifungal agent,and cross-linking agents of poly?vinyl alcohol?for battery separations.So getting DFF is very important to society and life.Polyoxometalates?POMs?,as one kind of significant metal oxide clusters with unique structure and properties.How to carry out corresponding catalytic biomass conversion studies is of great significance for the expansion of biomass utilization and POMs catalytic research.Based on this,we have designed a molybdenum-vanadium containing polyoxometalate catalyst and its performance in oxygen oxidation of 5-HMF.1.H₅PMo₁₀V₂O₄₀/chitosan nanofibers?HPMoV/CS-f?had been synthesized using electrospinning method,the catalyst was characterized by Infrared spectrum?IR??X-ray powder diffraction?XRD??Phosphorus nucleus(³¹P NMR)and X-ray photoelectron spectroscopy?XPS?to define the composition and structure and applied to the oxidation of5-HMF.The best result for reaction is under the condition of 5-HMF 100 mg,120oC,0.8 MPa O₂,4 mL solvent,and catalyst amount of 60 mg for 6 h.The conversion of 5-HMF reached96.2%,the yield of DFF was 94.1%,and the selectivity of DFF was 97.8%.Decorating chitosan nanofibers by POMs generated enhanced catalytic activity by emerging their unique individual properties of redox ability,basic property,and nanofiber structure of higher surface area.After the end of the reaction,the catalyst was recycled,and the activity was not significantly decreased after repeated 5 experiments.The catalyst structure was stable before and after the reaction,and remained basically unchanged.2.The?NH₄?₅H₆PV₈Mo₄O₄₀/Ca₁₀?PO₄?₆?OH?₂ solid catalyst?NPVMo/HAP?was designed and synthesized,and characterized by IR,XRD and so on.Explore the optimal conditions:126mg 5-HMF,10 mL solvent,70 mg of catalyst,at 130°C,O₂ is introduced at atmospheric pressure,and the reaction is carried out for 8 h.The conversion of 5-HMF was 96%,the yield of DFF was 83.8%,and the selectivity of DFF was 87.3%.Its catalytic activity is mainly derived from the oxidation activity center of Mo and V and the strong acidity of Br?nsted and the basicity of hydroxyapatite.After the reaction,the catalyst was recycled and reused six times,and the activity was not significantly lost.It was found by IR,XPS and so on,that the polyoxometalate anion structure did not change,and the leaching amount was about 5.8%.The stability of the catalyst structure remained unchanged before and after the reaction.3.?NH₄?₅H₆PV₈Mo₄O₄₀/CeO₂ nanofibers?NPVMo/CeO₂-f?had been synthesized using electrospinning method,which realized highly efficient oxidation of 5-HMF to DFF.Decorating CeO2 by POMs generated enhanced catalytic activity by emerging their unique individual properties of redox ability,basic property,and nanofiber structure of higher surface area.As results,the catalyst was found to be most active in aerobic oxidation of 5-HMF to give86.7%yield of DFF at 98%conversion of 5-HMF.Optimal condition:126 mg 5-HMF,10mL solvent,70 mg of catalyst,at 130°C,reaction tume is 8 h..Moreover,The catalyst showed good stability and duration for being reused at least seven times without obvious leaching of POMs from CeO₂.