Study On The Reduction Of 5-hydroxymethylfurfural To 2,5-dimethylfuran Catalyzed By Non-precious Bimetallic Borat

As the only renewable resource that can be used as both a material and an energy source,biomass is characterized by its wide distribution,easy access,rapid regeneration and large reserves.It can be used as a supplement and substitute for fossil resources.The 2,5dimethylfuran（DMF）which is derived from biomass-based platform compound 5-hydroxymethylfurfural（HMF）has the advantages of high energy density,high octane number and low viscosity.It is an ideal next-generation clean fuel additive for internal combustion engines.DMF can also undergo a Diels-Alder reaction with ethylene to produce p-xylene,an important organic synthesis raw material.However,currently reported catalytic systems for DMF suffer from low reduction efficiency,which greatly limits the application of DMF.To address the problem of low catalytic efficiency,the key lies in the design of high-efficiency catalysts.The catalytic reduction of HMF to prepare DMF involves a multi-step series of reaction processes including hydrogenation and hydrogenolysis,which requires the catalyst to contain two style of active sites for hydrogenation and C-O bond breaking.After a systematic study of the catalytic system for reducing HMF to prepare DMF,we have fabricated two bimetallic catalysts.These two catalysts have been shown to perform well in different hydrogen donor catalytic systems.Metal borate catalysts prepared by simple chemical reduction methods have many advantages,such as coordination unsaturated,uniform structure,abundant sites,and adjustable structure.In order to solve the problem of low catalytic efficiency of HMF reduction,a Ni_1.52Fe_0.36BO_x（Ni-Fe bimetallic borate）catalyst was prepared by chemical reduction method based on the principle of HMF hydrogenation and hydrogenolysis reaction.It can obtain 99%DMF yield under green ethanol as solvent at 160°C,1MPa H₂,and 1h.The DMF generation rate can reach 16.5mmol _DMF·g_cat^-1·h^-1,which is significantly higher than the existing literature.The catalyst characterization and experimental results indicate that the Ni_1.52Fe_0.36BO_x catalyst has an amorphous structure.The addition of Fe species leads to the formation of electron-rich metal Ni sites and acidic sites,which favor the activation of hydrogen and the cleavage of hydroxyl groups.The presence of abundant catalytic sites allows the catalysts to achieve good catalytic performance.Prepared Ni-Fe bimetallic catalysts have excellent catalytic properties and universal applicability to a variety of biogenic unsaturated aldehydes.In order to avoid the use of hydrogen in the hydrogenation and hydrogenolysis process,we continues to synthesize Cu-Zr bimetallic borate catalyst by chemical reduction method,which can use isopropyl alcohol as a green and safe hydrogen donor to catalyze the reduction of HMF to prepare DMF efficiently.The Cu₁₀Zr_0.39BO_x（Cu-Zr bimetallic borate）catalyst showed the best catalytic activity,and the DMF yield reached 98%at 180°C and 3h.The DMF formation rate reached 5.4mmol _DMF·g_cat^-1·h^-1,which was superior to the isopropyl alcohol transfer hydrogenation catalyst system reported in the literature.Experimental results and characterization of Cu₁₀Zr_0.39BO_x show that the Zr in the catalyst is uniformly dispersed in the form of a single atom and strongly interacts with the Cu O_x species,which alters the valence distribution of Cu sites and the metal dispersion at the catalyst surface.It has also been shown that doping of the Zr species in Cu₁₀Zr_0.39BO_x has a stabilizing effect on the Cu O_x species.The bimetallic catalyst(Cu₁₀Zr_0.39BO_x)is much more stable than the monometallic Cu O_x catalyst.In summary,two efficient bimetallic borate catalysts have been synthesized and used to catalyze the reduction of HMF to prepare DMF systems.Experimental results show that the addition of a second metal modifies the acidity and electron distribution of the catalysts,effectively increasing their activity.The addition of Fe species made Ni-Fe bimetallic borate catalyst(Ni_1.52Fe_0.36BO_x)form electron-rich metal Ni sites and acidic sites,which greatly promoted the hydrodeoxidation efficiency of HMF.The addition of monatomic Zr modified Cu O_x species on the surface of Cu₁₀Zr_0.39BO_x,showing excellent catalytic activity.This paper provides new applications for the bimetallic borate catalysts with high reduction activity,and some achievements have been made in the field of DMF preparation for biomass-based fuels.