Study On The Selective Catalytic Oxidation Of 5-hydroxymethylfurfural With Anderson Type Heteropolyacid

In recent years,China’s increasing demand for oil has led to an increase in oil imports and an increase in demand for alternative fuels.As a sole renewable organic carbon source,biomass energy research has also attracted extensive attention.5-Formyl-2-furancarboxylic acid（FFCA）is an important biological module material with broad application prospects in the fields of synthesis,chemical intermediates and medicines.5-Hydroxymethylfurfural（HMF）has many oxygen-containing functional groups,so selective oxidation of FFCA is relatively difficult and rarely studied.In the first part,Fe-Anderson type heteropoly acid Na₃H₆FeMo₆O₂₄·5H₂O（FeMo₆）was innovatively used to as a catalyst oxidize HMF to FFCA with high selectivity.The FeMo₆ catalyst was prepared by recrystallization and characterized by means of XRD,UV-vis,FT-IR,TG,ICP-AES and XPS.By comparing catalyst characterization and activity data,it is found that Mo⁵⁺and many surface oxygen species are closely related to catalytic performance.The experiment found that when N-methylpyrrolidone（NMP）was used as the reaction solvent and the molar ratio of HMF and K₂CO₃ was 0.5,the maximum FFCA yield could be obtained.Under the best conditions（HMF/K₂CO₃/Catalyst=1/0.5/0.08,100 ^oC,8 h）,in NMP solvent,the maximum yield of FFCA can reach 75%.Most importantly,the catalytic system can be carried out under normal pressure and the reaction conditions are very mild.2,5-Diformylfuran（DFF）is a key platform chemical that has been widely used in the synthesis of pharmaceutical intermediates,antifungal agents,organic conductors,macrocyclic ligands,and furan resins.In the second part,based on the concept of biomimetic catalysis,the reaction is skillfully decomposed into multi-step redox microcirculation to realize the high activity and high selective oxidation of HMF to the target product DFF.Anderson bifunctional catalyst CeCu（OH）₆Mo₆O₁₈ with similar properties to oxidase was prepared by ion exchange method,in which the cation Ce⁴⁺species was used as the electron transfer medium（ETM）and the anion[Cu（OH）₆Mo₆O₁₈]^4-was used as the electron donor.Through structure-activity analysis,it was found that the Mo⁵⁺and Ce⁴⁺species in the catalyst played a vital role in the oxidation of HMF to DFF.With p-chlorotoluene as the solvent,the yield of DFF is as high as 99%.This biomimetic catalytic concept provides an efficient method for the precise conversion of biomass.In the third part,a new method for the selective oxidation of HMF to DFF was developed by using the Anderson type heteropoly acid catalyst[(C₁₈H₃₇)₂N（CH₃）₂]₆Mo₇O₂₄,[C₁₂H₂₅N（CH₃）₃]₆Mo₇O₂₄ and[（C₄H₉）₄N]₆Mo₇O₂₄4 modified by quaternary ammonium salt cation.The catalyst was prepared by ion exchange and systematically characterized by FT-IR,TG and XPS techniques.It was found that the percentage of Mo⁵⁺species is closely related to the catalytic performance.The solvent effect has a significant effect on the catalytic performance,and the best solvent is p-chlorotoluene.Under the best conditions（catalyst mass=40 mg,130 ^oC,8 h）,HMF is oxidized under the action of[(C₁₈H₃₇)₂N（CH₃）₂]₆Mo₇O₂₄ catalyst to produce DFF with a yield of 99%.Finally,the mechanism of this system is explored.