The Study On The Synthesis Of γ-Valerolactone Based On Carbon Supported Non-Noble Metal Catalyst

With the continuous consumption of fossil energy,disastrous events such as heat waves,droughts and sea level rise occur frequently.In response to the growing climate crisis,carbon neutral planning has become a global consensus,and the substitution of low-carbon or zero-carbon renewable energy for fossil energy in the preparation of bulk chemicals is considered to be an important way to achieve this goal.Biomass is considered to be the only zero-carbon energy in many emerging renewable resources.The high-value conversion of biomass,especially its platform molecules,has become a very active research field.As an important fine chemical,γ-valerolactone was widely used in lubricants,plasticizers,oil additives and other fields.Under the background of carbon neutralization,it is undoubtedly of great economic,environmental and social significance to realize the green production ofγ-valerolactone from bio-based levulinic acid as the starting material.However,due to the intrinsic acidity of levulinic acid and multiple conversion routes,the construction of catalysts with high stability and high activity has become an urgent problem in this field.In order to solve the above problems,several non-noble metal catalysts with high stability and activity were constructed based on the confinement effect of carbon materials,and the directional and controllable conversion of levulinic acid（derivatives）was realized.The structure-activity relationship and action mechanism of the catalysts were systematically studied by means of catalyst characterization technology.The main contents of this thesis are as follows:1.Nitrogen-doped carbon material confined cobalt-based catalyst（Co@NC-800）was constructed by in-situ pyrolysis strategy.The catalyst shows good catalytic performance in the research of aqueous directional conversion of levulinic acid（LA）intoγ-valerolactone,namely,the yield ofγ-valerolactone is not less than 99%.The catalyst can still maintain high activity after being used for 10 times.The results of catalyst characterization and control experiments show that the good activity of the catalyst is mainly due to the synergistic effect of Co⁰,Co-Nx and Co₃O₄;The stability of the catalyst is mainly attributed to its core-shell confinement structure.2.Co@CN catalysts derived from MOFs were prepared using ZIF-67 as the substrate and the strategy of surface confined pyrolysis.The conversion of ethyl levulinate（EL）was100%and the yield ofγ-valerolactone was 97%under the optimum reaction conditions（H₂pressure 2 MPa,reaction temperature 200℃and reaction time 6 h）.The catalyst was used continuously for 7 times and no obvious decrease in catalytic performance was observed.3.Co-Zn/NC catalyst was prepared using ZIF-8 as support by the coupling strategy of urea co-precipitation and pyrolysis.The yield ofγ-valerolactone was 98%under the conditions of hydrogen pressure of 0.5 MPa and reaction temperature of 160℃.The results of catalyst characterization show that the excellent activity of the catalyst is most likely due to the synergistic effect of elemental cobalt and Lewis’s acid-base catalytic sites.