Synthesis Of HMF And FDCA From Agricultural Waste To Bio-based Platform Molecules

With the aggravation of global environmental problems and the shortage of fossil resources,it is particularly important to seek environmentally friendly renewable chemicals and fuels that can replace fossil resources.As a typical biomass-derived product,5-hydroxymethylfurfural（HMF）is one of the most important platform molecules,as its chemical structure allows the preparation of various high value-added products via catalytic routes.2,5-Furandicarboxylic acid（FDCA）produced after oxidation of HMF,is a promising bio-derived building block and valuable monomer of polyethylene furandicarboxylate（PEF）being considered as a future alternative to polyethylene terephthalate（PET）.In this paper,based on microwave heating technology,the homogeneous catalyst Al Cl₃ was used to catalyze the conversion of glucose to HMF,and then the supported catalyst Ru/Al₂O₃ was used to catalyze the oxidation of HMF to prepare FDCA monomer.The influence of catalytic conditions on the yield of the target product was analyzed systematically.The supported catalyst was prepared from biomass carbon,and the FDCA was directly produced by using cellulose as raw material by one-pot method.It is hoped to provide some feasible and valuable ideas for the development of efficient catalytic system of biomass conversion into high value-added platform chemicals.The main research contents and results of the study are as follows:（1）Through the use of microwave technology and green solvent system consisting ofγ-valerolactone（GVL）and water,together with inexpensive and low-toxicity catalysts Al Cl₃,glucose was directly converted to 5-hydroxymethylfurfural（HMF）in a biphasic reaction system.The influence of various catalytic reaction conditions on the reaction outcome was investigated,and the unique phase separation phenomenon of the reaction product was further analyzed to evaluate the catalyst recovery and solvent reuse performance.During the optimization process,factors such as microwave power,reaction time,catalyst dosage,and solvent ratio were examined for their significant impact on the product yield.The optimized reaction condition was determined to be 2mmol of Al Cl₃ catalyzing 1 g of glucose under 220 W microwave radiation,leading to a final HMF yield of 74.04%in 10 minutes.Furthermore,the recovered catalyst retained a certain level of catalytic activity for up to five cycles of experiments.（2）To more effectively promote the oxidation of HMF to produce 2,5-furandicarboxylic acid（FDCA）,a low-content ruthenium-loaded alumina catalyst was prepared,and a sustainable microwave catalytic reaction system was established to inject oxidants and alkaline solutions to reduce side reactions.Specific studies were conducted on the effects of different heating conditions,catalyst and oxidant amounts on the HMF conversion rate and FDCA yield.The optimized experimental conditions were the use of 0.08 g of catalyst under 200 W of microwave irradiation for 10 min,with oxidant and alkali solution injection rates of 0.8 m L/min and 1 m L/min,respectively,the final FDCA yield was 82.24%,and the HMF conversion rate was98.33%.In addition,the recyclability of the catalyst was tested,and after the sixth cycle,the catalyst still yielded 70.88%of FDCA,and the reasons for the change in catalytic activity were further analyzed,along with potential solutions.（3）Building upon the aforementioned study,a one-pot approach was used to directly prepare 2,5-furandicarboxylic acid（FDCA）from corn cob biomass using a carbon-based catalyst prepared from corn cob biomass,which was loaded with ruthenium and sulfonated.The catalysts were characterized and tested before being used for direct catalysis of the corn cob pretreatment mixture to produce FDCA,and the catalytic performance was analyzed.In addition,the yield variation of FDCA prepared under different reaction conditions for both catalysts were studied in detail.Results showed that using 0.12 g of Ru/C catalyst under 200 W,27%yield of FDCA was obtained directly catalyzing the pretreated corn cob mixture,while the sulfonated carbon catalyst yielded approximately 19%under the same conditions with an injection rate of 1.4 m L/min of oxidant H₂O₂.