Selective Hydrogenation Of 5-hydroxymethylfurfural Over Nitrogen-doped Carbon-confined Cobalt-based Catalysts

Hydrogenation of 5-hydroxymethylfurfural（5-HMF）to 2,5-dimethylfuran（2,5-DMF）is an attractive route for the preparation of renewable fuels.The development of low cost and high efficient hydrogenation catalysts and catalytic reaction systems is the key to the industrialization of 2,5-DMF production.Non-noble metal catalysts such as Cu and Co have obvious cost advantages due to their low price.However,how to improve the activity and stability of the catalyst is the main challenge.In this thesis,we first carried out the research on Co-MOFs pyrolysis-derived nitrogen-doped carbon-supported cobalt-based catalysts.A nitrogen-doped carbon-confined cobalt monometallic catalyst was prepared by a series of heat treatment of cobalt-based metal-organic framework material ZIF-67 as a precursor,and the performance of the catalyst was explored under different reaction conditions.It was found that the best performance of the catalyst was obtained in H₂/N₂（4%）mixed atmosphere after heat treatment at 440°C for 8h and 900°C for 2h.With 2-butanol as the reaction solvent,at the reaction temperature of 180^oC and a hydrogen pressure of 2.0 MPa,after 4 hours of reaction,the catalyst achieved 100%of HMF conversion and 82.9%of DMF selectivity.The structure and active components of the catalyst were analyzed by various characterization methods,it was found that the precursor after heat treatment of the mixture formed a carbon-based material covered by carbon nanotubes,which retained the basic framework of ZIF-67,and the metal particals were confined in the carbon nanotubes,the Co⁰ and CoN_x were the main active components of the catalyst.In order to further improve the performance of the catalyst,the second active metal component copper was introduced.Using 2-methylimidazole as the nitrogen source,glucose and 2-methylimidazole as the carbon sources at the same time,a novel popcorn-like nitrogen-doped carbon-confined Cu Co bimetallic catalyst was successfully prepared.When2-Butanol was used as the reaction solvent,and the reaction was carried out at 180°C under a hydrogen partial pressure of 2 MPa,after 4 hours of reaction,the catalyst achieved 100%of HMF conversion and 93.7%of DMF selectivity.After five cycles,no distinct decrease was observed in either HMF conversion or DMF selectivity.This indicates that the catalyst is highly stable and adequately reusable.The structure of the Cu Co bimetallic catalyst was characterised using XRD,XPS,SEM,and TEM.It was found that the synergistic effect of Cu⁰ and Co⁰/Co O_x provided high activity during the reaction,and the high activity of the catalyst was closely related to its unique popcorn-like structure.In addition,2-butanol is not only be the solvent of this reaction,but also provides the hydrogen in this reaction.