Study On The Preparation Of 5-hydroxymethylfurfural By Efficient Dehydration Of Fructose And The Oxidative Derivation 2,5-furandicarboxylic Acid

Using carbon-neutral biomass to prepare high value-added chemicals is an important way to replace fossil energy with biomass energy,which is greatly significant to the sustainable development of energy.5-Hydroxymethylfurfural（HMF）is a bridge between biomass and fossil industry,and 2,5-furandicarboxylic acid（FDCA）obtained by HMF upgrading oxidation can be used as a substitute for petroleum-derived monomer terephthalic acid（TPA）used in traditional polyester industry.The construction of catalyst is the key to realize efficient preparation of HMF and FDCA.Firstly,biochar-based solid acid catalyst was prepared from agricultural waste rice straw for the dehydration of fructose to HMF.Secondly,in order to realize HMF upgrade oxidation to FDCA,supports with different Zr O₂ crystal phases were prepared and Au nanoparticles were loaded.The effects of oxygen vacancy（O_v）concentration,Lewis acid in Zr O₂ and metal-support interaction on catalytic activity were investigated.Finally,the best Zr O₂ crystal phase was selected as the research object and the carrier with higher O_v concentration was synthesized with the help of citric acid（CA）.Au Pd bimetallic nanoparticles were loaded on the carrier to realize the efficient oxidation of HMF to prepare FDCA.（1）The preparation of HMF by dehydration of fructose with crop straw biomass carbon-based solid acid as catalystBiochar-based solid acid catalyst was prepared from rice straw,which was used to efficiently catalyze the dehydration of fructose to HMF under microwave irradiation.The physical and chemical properties of a series of biochar-based solid acid catalysts were analyzed by SEM,Raman,XRD,BET,NH₃-TPD and XPS,and the effects of pyrolysis temperature,microwave and oil bath heating methods on catalytic performance were explored.The results showed that the biochar obtained by pyrolysis at 700℃had moderate acid content after sulfonation,which can effectively improve the conversion efficiency of fructose under microwave irradiation.Microwave-enhanced catalysis can be attributed to the combination of dipole polarization of sulfonic acid groups with microwave response and biochar carriers with microwave absorption ability.Under the optimum reaction conditions（120 W,120℃,5 min）,the best HMF yield of 92.6%can be obtained,which was significantly higher than the catalytic effect of traditional heating.（2）The preparation of FDCA by HMF selective oxidation catalyzed by Zr O₂@HNTs loaded with Au nanoparticlesPreparing high value-added FDCA from HMF is an important way to promote the biomass energy development.Zr O₂ samples coated on the surface of Halloysite nanotubes（HNTs）were synthesized and used as supports for loading Au nanoparticles.The supported metal catalysts with Au-Zr O_x active interfaces were successfully designed.The crystal phase of Zr O₂ was adjusted by changing the calcination temperature,so that the number of active sites were reasonably regulated.The physical and chemical properties and catalytic activity of catalysts showed that O_v was benefit to enhance O₂ adsorption ability of catalysts.At the same time,the interface active sites promoted the activation of O₂,which made it easier to produce active oxygen species（superoxide radical,·O₂^-）.In addition,in-situ FT-IR and adsorption experiments showed that catalyst with higher Lewis acid concentration had stronger adsorption ability for HMF and key intermediate HMFCA,which would speed up the rate-determining step.The experimental results showed that 650℃-Au/2L-Zr O₂@HNTs had higher O_v and Lewis acid concentration,and the best FDCA yield（99.4%）was obtained at 3 h.（3）The preparation of FDCA by selective oxidation of HMF catalyzed by Au Pd bimetal in cooperation with oxygen vacancyThe O_v,Lewis acid concentration and metal-support interaction had important effects on catalytic performance.Therefore,the Zr O₂ with optimal crystal phase was selected as the research object.CA and carrier with amorphous Zr O₂ were calcined at650℃after fully grinding to further improve the O_v concentration of catalyst.Moreover,supported metal catalysts Au_xPd_y/Zr O₂@HNTs-z CA were prepared by supporting Au Pd bimetallic nanoparticles on the surface of carrier with co-reduction method.The catalytic performance results showed that the best FDCA yield was 99.5%when Au₃Pd₁/Zr O₂@HNTs-1.0CA reacted for 25 min.The physical and chemical properties of catalyst showed that the excellent catalytic performance of catalyst was mainly attributed to the active interface of Au Pd-Zr O_x.The higher concentration of O_vin Zr O₂ improved the adsorption and activation ability of catalyst for O₂,and the higher Lewis acid concentration further enhanced the adsorption ability of catalyst for reaction substrates.The synergistic effect of Au Pd bimetallic nanoparticles promoted the activation of reactants and intermediates.The rate-determining step was accelerated,and the selectivity and FDCA yield were improved.