Study On The Electrocatalytic Oxidation Of 5-hydroxymethylfurfural Over Manganese-based Catalyst

Synthesis of high value-added chemicals by electrochemical conversion of biomass is an important direction in the development of chemical industry.5-hydroxymethylfurfural（HMF）is recognized as the most promising and representative new biomass platform compound in recent years.It can be obtained by acid catalytic hydrolysis and dehydration of cellulose.At the same time,various high value-added compounds can be prepared by oxidation,hydrogenation,esterification,polymerization and other chemical reactions.Its oxidation products,2,5-dimethyl furan（DFF）,5-hydroxymethyl-2-furan formic acid（HMFCA）,2-formyl-5-furan formic acid（FFCA）and 2,5-furan diformic acid（FDCA）,are important fine chemicals,pharmaceutical intermediates and material intermediates.2,5-furanediformic acid（FDCA）was also recommended by the US Department of Energy as one of 12 biomass based platform compounds of significant value to replace petroleum-based monomer terephthalic acid（PET）in the preparation of renewable biobased plastics.Electrochemical catalytic oxidation of 5-hydroxymethylfurfural to produce high value-added chemicals has become a hot topic in the current research field.Compared with traditional Thermocatalytic methods which require precious metal catalyst and high temperature and pressure conditions,electrochemical oxidation of 5-hydroxymethylfurfural has been widely concerned because of its advantages such as mild reaction conditions,high selectivity of products and stable catalyst.Currently,researchers have developed a variety of electrochemical catalysts,among which transition metal catalysts are considered to be one of the most promising development directions.In this paper,a relatively cheap transition metal was used to study the electrocatalytic oxidation of HMF.This paper draws the following conclusions:（1）Theε-MnO₂ catalyst was prepared and theε-MnO₂/bp catalyst was obtained by calcination and constant-current treatment.The electrochemical catalytic oxidation performance of the catalyst under acidic conditions was investigated.Under the same reaction conditions,ε-MnO₂/bp electrocatalytic oxidation activity of HMF is the best,the conversion rate of HMF is 65.49%,the oxidation rate of HMF is 0.21 h^–1,and the yield of FDCA is 4.87%.The oxidation path of HMF is HMF→DFF→FFCA→FDCA,and the apparent activation energies ofε-MnO₂/bp catalysts are 25.52,22.12,16.21 k J mol^–1,respectively.The electrochemical oxidation performance of HMF under different reaction conditions was further studied,and FDCA products were obtained under 1.6 V voltage and acidic electrolyte conditions.The XPS characterization of the catalyst before and after the reaction indicated that the electrocatalytic oxidation activity of HMF was positively correlated with the lattice oxygen content and the ratio of Mn⁴⁺/Mn³⁺.（2）A variety of different metal manganese spinel（AMn₂O₄,A is Ni,Cu,Fe,Co）catalysts were prepared by hydrothermal method,and their electrochemical catalytic oxidation performance of HMF was studied.The results show that NiMn₂O₄ catalyst has the best oxidation performance of HMF.In 25℃,1.5 V（vs.RHE）,1 M KOH solution for 5 h,the conversion of HMF was complete,the yield of FDCA was 87.24%.In this paper,the electrochemical activity of Ni-Mn catalysts with different proportions was further investigated.By comparing the catalytic activity data of Ni₂MnO₄,NiMnO₄,NiMn₂O₄ and Mn₃O₄,NiMn₂O₄catalyst had the best HMF oxidation performance.NiMn₂O₄ catalyst reacts at 1.5 V（vs.RHE）for 4 h,and the conversion rate of HMF is 96.08%,the oxidation rate of HMF is 0.81 h^–1,the yield and selectivity of FDCA are 79.41%,82.65%,and the average current density of the reaction is 8.17 m A cm^–2.