Design Of Iron-Based Catalyst And Its Catalytic Performance For 5-Hydroxymethylfurfural Oxidation

In recent years,the depletion of fossil energy has been increasing,and the greenhouse effect has become more and more serious.Therefore,the conversion of renewable resources to high value-added chemicals has received increasing attention.The efficient conversion of abundant biomass and its derivatives into urgently needed fine chemical products by catalytic method is the commanding height of science and technology that all countries are seizing.5-hydroxymethylfurfural（HMF）is an important platform molecule derived from plant biomass.The highly selective catalytic oxidation of HMF to 5-hydroxymethyl-2-furancarboxylic acid（HMFCA）,5-formyl-2-furancarboxylic acid（FFCA）and 2,5-furandicarboxylic acid（FDCA）by green chemistry and sustainable development is of great significance.In this paper,a series of highly active iron-based non-precious metal heterogeneous catalysts were prepared for the selective catalytic oxidation of HMF to HMFCA,FFCA and FDCA.The main research contents and results are as follows:（1）Nitrogen-doped biomass carbon（N/C）was prepared by using sycamore leaves as carbon source and urea as nitrogen source.A series of composite catalysts Fe TPP-N/C-x were prepared by ultrasonic compounding with iron porphyrin（Fe TPP）,and their catalytic performance in HMF oxidation was studied.The physical and chemical properties of the catalyst were characterized by a series of methods.The effects of the amount of alkaline additives,reaction temperature,reaction time and oxygen pressure on the reaction were investigated.When the ratio of iron porphyrin to nitrogen-doped porous carbon is 1:1,the catalyst exhibits good catalytic activity.The main product of HMF oxidation is HMFCA,and the yield can reach89.8%.Recyclability and thermal filtration experiments proved that the catalyst had good recyclability and thermal stability.（2）Iron phthalocyanine（FePc）and copper-iron hydrotalcite（LDH）were intercalated by ultrasonic method,and FFCA was prepared by selective catalytic oxidation of HMF in the presence of H₂O₂.The physical and chemical properties of the catalyst such as morphology,crystal phase,thermal stability,specific surface area and surface properties of the catalyst were observed by various characterizations.The effects of reaction temperature,reaction time,dosage of alkaline additive,H₂O₂ and catalyst on the reaction were investigated.Under the optimal reaction conditions,the catalyst showed good catalytic activity,the conversion of HMF was 85%,the main product was FFCA,and the yield was 89.8%.The catalyst has no significant loss of catalytic activity after 5 cycles and has good stability.（3）NiFe-LDH was prepared,and then NiFeS and NiFeP-400 catalysts were obtained by hydrothermal vulcanization with thioacetamide at 120°C or phosphating with sodium hypophosphite at 400°C,respectively.X-ray diffraction（XRD）and high-resolution transmission electron microscopy（HR-TEM）analysis showed that these catalysts were dominated by Fe Ni₂S₄ and Fe Ni₂P,respectively.The catalytic activity of each catalyst was optimized by exploring the effects of reaction solvent,temperature,oxidant and time on HMF conversion and product distribution.Under the optimal conditions,the conversion of HMF was100%and the selectivity of FDCA was 83.2%over NiFeS catalyst.The catalytic activity of NiFeP-400 catalyst is basically the same,the conversion of HMF is 100%and the selectivity of FDCA is 82.7%.Both catalysts show excellent stability in the recirculation experiment,and the catalyst has good magnetic properties that can be collected by magnets.Based on the experimental results,we proposed a similar reaction mechanism for the oxidation of HMF to FDCA on two catalysts.