Study Of Catalytic Hydrodeoxygenation Reaction Of Biomass Derivatives

With the over-exploitation of the fossil resources,finding sustainable green alternative resources is an urgent issue.As the most abundant renewable resource on the earth,biomass has the advantages of vast reserves,wide distribution,green and clean,so it has been widely concerned in recent years,and is considered to have the potential to replace fossil resources for the production of fuels and high value-added chemicals and materials.Catalytic conversion is the effective way to realize the transformation of biomass into fuels or important chemicals,and the construction of efficient catalytic system is the key for the catalytic conversion of biomass.Selective hydrodeoxygenation is an important reaction process to realize the conversion of biomass to fuels or useful chemicals.In this thesis,efficient catalysts have been constructed by changing the type of active metal and regulating the properties of the support,and high value-added chemicals,such as 2,5-dimethylfuran,γ-valerolactone and cyclohexanol,were obtained from the conversion of the biomass derivatives containing different carbon and oxygen structures（5-hydroxymethylfurfural,levulinic acid and guaiacol）.The main research contents and innovations are as follows:（1）2,5-dimethylfuran can be used as an important additive for liquid fuels and as an important chemicalwhich can be generated by selective hydrogenation and deoxidation of biomass-derived 5-hydroxymethylfurfural.However,it is challenging to realize this process without any additives under mild conditions.Here,we designed and prepared a palladium catalyst by supporting palladium nanoparticles on a zirconium-based metal-organic framework（Pd/MOF-808）,which could efficiently catalyze the hydrogenolysis of 5-hydroxymethylfurfural into 2,5-dimethylfuran at 100^℃ without any exogenous additives.In addition,the catalytic acitivity of the Pd/MOF-808 catalyst did not decrease obviously in several cycles of reuse.（2）As a promising biomass platform molecule,levulinic acid can be used to synthesize many value-added chemicals through hydrogenation and deoxidation,among whichγ-pentolactone has attracted wide attention due to its excellent physical and chemical properties.Here,the metal-organic framework（MOF）Ru/NH₂-MIL-125 was prepared by one-pot method as the precursor of catalyst,and the single ruthenium atom catalyst Ru/TiO₂@CN with ultra-low loading was prepared by calcination at 750 ^℃ in nitrogen atmosphere.Ru/TiO₂@CN catalyst exhibited excellent catalytic activity for the conversion of levulinic acid at room temperature,which producedγ-valerolactone with both selectivity and yield of near 100%.The conversion frequency（TOF）could reach 278 h^-1 with 100%conversion of levulinic acid,which was about 35 times higher than the commercial Ru/C catalyst.The Ru/TiO₂@CN catalyst was reused for several times,and their activities did not change noticebly,indicating of the excellent stability of the catalyst.（3）Cyclohexanol is a widely used chemical,which is mainly produced by oxidation of fossil materials.The selective hydrodeoxygenation of lignin derivatives has great potential in the production of cyclohexanol,but it is difficult.We designed ceria supported ruthenium single atom catalyst（Ru/CeO₂-S）,and realized for the first time the hydrodeoxygenation of aromatics in the single atom catalytic system.The Ru single atom catalyzed the hydrogenation of the lignin-derived guaiacol and cleavage of the C-O（R）bond with the C-O（H）bond retained,thus affording both the selectivity and yield of cyclohexanol up to nearly 100%.Based on the experiments and density functional theory calculations,Ru-O-Ce catalytic sites are formed on the catalyst which effectively realized the hydrogenation of the aromatic ring and cleavage of the C-O（R）bond.This work created a precedent of the hydrodeoxygenation of the aromatics by single-atom catalysis with low metal loading,and and provided a new way for the conversion and utilization of lignin resource.