Research On The Selective Oxidation Of Bio-Derived 5-Hydroxymethylfurfural To 2,5-Diformylfuran

The insufficient reserves of fossil fuels and the increasing environmental pollution hinder the sustainable development strategy.As the only carbon-containing renewable energy on earth,biomass can synthesize liquid fuels such as biodiesel and high value-added chemical products through chemical conversion and biological fermentation,and has become the most attractive material in modern energy and chemical research.5-hydroxymethylfurfural（5-HMF）,as an important biomass-based platform compound,is derived from biomass and can be used to manufacture a variety of drugs,antifungal agents,polymers and so on.Conversion is a key method to achieve reasonable and efficient utilization of biomass.Among them,5-HMF can be oxidized to obtain 2,5-furandiformaldehyde（DFF）which has a wide range of applications in the synthesis of fluorescent materials,medicine,organic conductors and so on.Therefore,the aerobic oxidation of 5-HMF to DFF has attracted a lot of researchers in the field of biomass value-added utilization.Aiming at the problems of high cost,easy deactivation of precious metal catalysts and low activity of non-noble metal catalysts in the 5-HMF oxidation system,two heterogeneous catalysts were developed including hydroxyapatite-supported manganese oxides（Mn O_x/HAP-X-T）and nitrogen-doped carbon material（NC-T）.Combined with the experimental results and characterization analysis,the oxidation activity and properties of catalysts were evaluated.In this paper,a series of MnO_x/HAP-X-T catalysts were prepared by precipitation method.The properties and morphology of the catalysts were analyzed by XRD,ICP,BET,SEM,XPS techniques.The Mn O_x/HAP-10.0-400 catalyst had larger specific surface area,the highest concentration of Mn⁴⁺and lattice oxygen.86.4%conversion of 5-HMF with 90.9%selectivity of DFF had been achieved using toluene as the reaction solvent at 120℃and 1.0 MPa O₂ for 12 h.In addition,the catalyst maintaind an excellent stability which can be used at least 4 times.Finally,based on the reaction results and characterization analysis,the possible reaction mechanism over Mn O_x/HAP-10.0-400 catalyst for the selective oxidation of 5-HMF to DFF was proposed.NC-T material was prepared by a simple process and examined as a metal-free catalyst for selective oxidation of 5-HMF.The results of reaction and characterization showed that the pyrolysis temperature in the preparation process had a significant effect on the activity of the catalyst.The NC-800 material exhibited the highest content of graphitic nitrogen and lattice defects as well as a larger specific surface area.As a result,the highest HMF conversion of 93.0%with DFF selectivity of 94.4%was obtained at110℃under 1.0 MPa O₂ pressure after 8 h in acetonitrile solvent.In addition,NC-800had excellent stability.The presence of graphiteic nitrogen species was significant for the formation of active sites on the surface of catalyst.The Oxygen radicals from O₂abidsorbed on the carbon atoms adjacent to the graphitic nitrogen were involved in the oxidation process of 5-HMF to DFF.