Study On Selective Catalytic Conversion Of Platform Compound 5-Hydroxymethylfurfural To Furan Derivates

Currently,biomass is one of the most promising renewable energy sources.Biomass resources have the advantages of wide distribution,abundant reserves and low cost of acquisition.They have attracted a lot of attentions.Compared with the currently widely used fossil resources,the use of biomass resources helps to maintain a balance of carbon.The content of this thesis mainly focuses on the high-value utilization of biomass resources,developing technical approaches for efficient conversion of biomass-based 5-hydroxymethylfurfural(HMF)and its’ derivatives to downstream oxidation products,such as 2,5-diformylfuran(DFF),2,5-furandicarboxylic acid(FDCA)and furan dimer-based aviation fuel precursor.First of all,a technical approach for the synthesis of DFF with high efficiency catalyzed by MnOx was studied.The manganese oxide catalysts were prepared using hydrothermal method by regulating the ratio of MnSO4·H2O to KMnO4,which were used for selective catalytic oxidation of HMF to DFF.Through the characterization of these manganese oxides,it was determined that they were divided into three types:αMnO2,β-MnO2 and δ-MnO2.Among them,α-MnO2 had the best catalytic performance.Under the optimal conditions,HMF conversion could reach 100%and DFF selectivity could reach 98.00%.Their characterizations revealed that the reduction initiation temperature,oxygen adsorption conditions on the surface,specific surface area,pore volume,particle size,dispersion and high-priced Mn element were the main factors affecting the effect of the catalyst.Secondly,a technical approach for the preparation of FDCA with high efficiency catalyzed by Ru/CeO2 was studied.A series of ruthenium catalysts were prepared using sodium borohydride reduction method in this thesis.Among them,the nano-ceria carrier supported ruthenium catalyst had the best performance.Nano-ceria carrier was prepared by the sol-gel method.Under the optimal conditions,the yield of FDCA could reach up to 99.82%from HMF.Ru/CeO2 showed good recycling performance.Through characterization,it was determined that the ruthenium catalysts prepared by the sodium borohydride reduction method had good dispersibility.It was also found that the specific surface area,the interaction between ruthenium and support had great influence on the catalytic efficiency.Finally,possible reaction paths were proposed by monitoring the changes of various products during the reaction.Ru/CeO2 catalyzed oxidation reaction of HMF to FDCA through two intermediates(DFF and HMFCA),and final step was oxidation reaction of FFCA to FDCA.The continued oxidation of FFCA was a rate limiting step in the selective catalytic oxidation process of HMF to FDCA.Then,a technical route for the preparation of FDCA by catalytic oxidation of a novel biomass-based furan platform compound 5-[(formyloxy)methyl]furfural(FMF)was studied.FDCA yield could reach up to 93.55%from FMF under optimal conditions.This yield was similar to that of using HMF as raw material.This confirmed the feasibility of replacing HMF by FMF to prepare FDCA.The study of reaction pathway showed that FMF and HMF had a reversible equilibrium in the reaction system,both of which can be oxidized to DFF.And then DFF was oxidized to FFCA.At the same time,the reaction path of HMF to HMFCA and FFCA also existed in the system.Finally,FFCA was oxidized to FDCA.The oxidation of FFCA to FDCA was the rate-limiting step of the whole reaction path.Finally,a technical approach for the preparation of furan dimer bis(5-methylfuran2-yl)methane(BMFM),a precursor of biomass aviation fuel,was studied.This approach used NaHSO4 as catalyst for the highly efficient condensation reaction of 5methyl-2-furan methanol(5-MFA)and 2-methylfuran(2-MF),which were downstream derivatives of HMF and furfural.Through catalyst screening and condition optimization,the best reaction conditions of condensation reaction to prepare furan dimer(BMFM)were as follows:the ratio of 5-MFA and 2-MF was 1:5,NaHSO4 dosage was 50%,acetonitrile reaction system,room temperature,10 min.BMFM yield was>99%under this condition.NaHSO4 could be recycled through simple filtration and drying after the reaction.Through the analysis and characterization of the reaction data,it was found that the crystallization water in the catalyst can promote the condensation reaction.The condensation reaction was mainly the nucleophilic addition process of 2-methylfuran and carbocation formed by dehydration of hydroxyl group on 5-MFA.The electrondonating substituents and conjugated structures on the furan ring could effectively promote the dehydration of hydroxyl group to form carbocation and the condensation reaction.