The Regulation Of Surface Structure Performance Of Cu/ZrO₂ Catalysts And The Study Of Their Catalytic Permance For Furfural Hydrogenation

With the depletion of fossil energy and the problem of environmental pollution caused by its overuse is becoming more and more serious,the effective utilization of biomass resources has gradually become the focus of research.Furfural(FFA),an important biomass platform molecule,can be converted through hydrogenation and hydrogenolysis processes to produce a series of chemical intermediates,fine chemicals and biofuel precursors.In recent years,researchers have found that FFA can be used to produce cyclopentone(CPO)by hydrogenation in the aqueous phase.As a kind of important intermediate molecules and organic solvent,CPO has wide application in the drug synthesis,synthetic rubber,spices,and other fields.Besides,with the process of condensation and hydrogenation,it can convert into fuel precursor and high density fuel,which is one of the important precursors for preparing biomass fuel.The reaction of FFA hydrogenation into CPO is green and cheap,which has important application value.At present,the research on this reaction system mainly focuses on precious metal(Pt,Ru,etc.)catalysts and non-precious metal(Cu,Ni,etc.)catalysts.Although the catalytic performance of non-precious metal catalysts is better,the reaction generally requires high temperature and high pressure,and the catalyst is poor in stability and low in reusability.Therefore,it is of great significance to explore the active sites of the catalyst by control the structure and properties of the catalyst surface and thus to improve its catalytic performance and stability.Copper-based catalysts are a commonly used hydrogenation catalyst and have a wide range of applications in furfural hydrogenation.Zirconium dioxide(ZrO2)is an oxide with good acidity and alkalinity on the surface.It has good physical and chemical properties and is a good catalyst carrier.Through the adjustment of the preparation method and the doping of other metal elements,the structural properties of ZrO2 can be enhanced.At the same time,the strong interaction between ZrO2 and the metal can further improve the catalytic performance of the catalyst.In this paper,through the regulation of the copper-based catalysts supported by the Mo-doped ZrO2 carrier,the effects of the acidity of the catalyst surface and the Cu species on the hydrogenated rearrangement of furfural to cyclopentanone were investigated.Based on the results,a highly-dispersed Cu/ZrO2 catalyst was prepared.The interaction between Cu and the support was enhanced by calcination,which further improved the catalytic activity,selectivity,and stability of the catalyst and the relationship between active sites and catalytic performance was studied in depth.(I)The molybdenum-doped ZrO2 carrier was prepared by coprecipitation method,and metal Cu nanoparticles were loaded by chemical reduction using sodium borohydride as reducing agent.The characterization of different series of catalysts shows that the doping of molybdenum is beneficial to reduce the crystallinity of ZrO2 and increase the acid strength of the catalyst surface,especially the Lewis acid content.The amount of sodium borohydride can regulate the reduction of Cu species on the surface of the catalyst.When the amount of sodium borohydride is five times of the molar amount of Cu,the reduction effect is best.Combined with the catalytic reaction results,the Lewis acid sites and Cu+ species on the surface of the catalyst are conducive to promote the rearrangement process and improve the selectivity of CPO.(II)The catalyst precursor was prepared by a combination of separate nucleation and aging steps assisted by a reduction-oxidation process,and was further reduced by different calcinations to obtain a highly dispersed copper-based catalyst supported on ZrO2.A series of characterization and catalytic experiments were performed to analyze the relationship between the structural properties of the catalyst surface and the catalytic properties.The results show that a certain calcination temperature can enhance the interaction between the ZrO2 support and metallic Cu,increase the content of Cu+ species on the catalyst surface,and maintain a rich Lewis acid sites.Under the synergistic effect of Cu0,Cu+ species and Lewis acid sites,the hydrogenation rearrangement of FFA to CPO was achieved at low pressure.In addition,the catalyst has high stability and the activity of the catalyst and selectivity to CPO are not significantly reduced after reused five times.