A Study On Catalytic Hydrogenolysis Of 5-hydroxymethylfurfural To 2,5-dimethylfuran

5-hydroxymethylfurfural(5-HMF)is considered as an important biomass platform compound,which can be used to prepare different high value-added chemicals and liquid biofuel through catalytic method.It has arisen as a key topic in the field of biomass catalytic conversion.It is found that 2,5-dimethylfuran(DMF)is a new kind of high-quality liquid fuel with high energy density and octane number.At the same time,it is also an important chemical intermediate,which can react with ethylene to produce paraxylene(an important industrial application chemicals)through Diels-Alder reaction.The preparation of DMF from 5-HMF is a hot topic at domestic and abroad.And the same time,the most essential issue is the construction of highly efficient catalytic system.Although transition metal catalyst has a very broad application,how to use non-noble metal catalyst to obtain high DMF selectivity in HMF hydrogenation is a scientific problem to be solved urgently.Therefore,a series of catalysts with non-noble metal cobalt as the active component were selected to improve the selectivity of DMF.In the first part,the Co/Beta-DA catalyst was prepared by a simple impregnation-reduction method based on the interaction between metal ions and hydroxyl nests in the deep dealuminized all-silicon Beta molecular sieve.It was found that the particle size,content and falling position of Co,the crystal type and pore structure of molecular sieve were closely related to the selective hydrogenation performance of 5-HMF.Moreover,the process conditions of the reaction were optimized and the catalytic mechanism of the reaction was also explored.Under the optimal reaction conditions(temperature,pressure,time,etc.),100% HMF conversition and 83 % DMF yield were achieved through Co/Beta-DA catalyst.In a word,this method provides a simple,low-cost and high-performance way for HMF hydrogenolysis to DMF.Although Co/Beta-DA has high DMF selectivity,the catalytic mechanism of Co is unclear.In this study,the two-dimensional nanosheet cobalt-based catalysts with different phases were prepared through temperature-induced phase transition method and applied to the reaction of HMF.Under the optimal reaction conditions,2D HCP-Co nanosheet catalyst will make the yield of DMF reach to 95.1% after 4 hours.In addition,XRD,TEM and other characterization have been used to prove the formation of catalysts.The hydrodeoxidation reaction mechanism of the system was proposed and theoretical calculation(DFT)was used to prove that HCP-Co had excellent hydrogenation performance.Considered that the hydrogenation reaction of HMF involves high temperature and high pressure,it is a great challenge for the stability of the catalyst.In order to solve the problem of catalyst stability,alloy species with excellent stability are formed by adding transition metals such as iron and nickel.Hexagonal boron nitride(h-BN)has excellent oxidation resistance and thermal stability which combination with the active component(alloy)can greatly improve the stability of the catalyst.FeCoNi/BN catalyst with the optimal ratio was applied to HMF hydrogenation reaction.Under optimal reaction conditions,the yield of DMF was 94.0%.At the same time,the stability of the catalyst was tested.After ten recovery experiments,the yield of DMF was still higher than 82%,which proved that the catalyst had excellent stability.FeCoNi/BN was characterized by XRD,TEM and XPS and the FeNi alloy structure was proved.Finally,thermogravimetric analysis(TG)and ICP elemental analysis were used to analyze the reasons for the slight decrease of catalyst activity.