Fabrication Of Non-noble Meta Catalyst Based On Metal Support Interaction And Their Application In Hydrogenation

Biomass is a renewable resource with abundant reserves on the earth,which is ideal new energy that can deal with the energy crisis caused by depleting fossil energy.Lignocellulose,biomass from a wide range of sources,whose derivatives such as vanillin and furfural can be transformed into fuels or high-value chemicals through various catalytic conversion processes,in which the catalyst plays a key role.Nonnoble metal catalysts have the advantages of low cost and easy availability,which have great potential in biomass conversion.Therefore,the design and synthesis of highefficiency non-noble metal catalysts is a meaningful research field.The metal support interaction(MSI)is an important effect in heterogeneous catalysis,which can adjust the electronic structure of active metals and stabilize active metals,playing a key role in the synthesis of efficient catalysts.This thesis based on the MSI effect,designed several high-performance catalysts,systematically studied the MSI effect in the catalysts that used reducible metal oxides or inert carbon as support.Various characterization methods were applied to determine the relationship between reaction and catalyst structure,and the influence of the MSI effect on the reaction was also discussed.The optimal conditions of the reaction were explored,and the reaction process and reaction mechanism were discussed.The main research contents are as follows:1.Active metal can easily form strong metal support interaction(SMSI)with metal oxide support,which is highly related to the exposed crystal plane of the metal oxide.In this work,three types of Cu/CeO2 with different morphologies and exposed facets were prepared,the relationship between SMSI effect and the facet of oxide support was studied,and the influence of this effect on liquid phase hydrogenation was also explored.Various characterization methods,including TEM,XPS,H2-TPR,were applied to determine the morphology,structure,chemical state and metal dispersion of these catalysts.It was found that the SMSI effectively improved the Cu dispersion and the stability of these Cu/CeO2 catalysts.The chemical state of Cu is affected by the SMSI effect with different intensity induced by different facets,as a result,these catalysts displayed significantly different catalytic performances.Besides,it is found that the SMSI effect is related to the metal loading,the SMSI effect would show greater influence at a lower metal loading.2.The above results show that too strong SMSI effect will inhibit the catalytic activity.To get the catalyst with higher activity,NiFe2O4(NFO)was used as the precursor to in-situ synthesize NiFe alloy catalyst(NiFe/NFO)with SMSI effect through the gradual reduction process of bimetallic ions.Benefiting from the synergistic effect of alloy and SMSI effect,the catalyst showed both high activity and high stability,the complete conversion of vanillin can be realized at room temperature,and the catalyst had no activity loss in the cycle experiments.H2-TPR,XPS and in-situ XRD were used to confirm the SMSI effect between NiFe alloy and NFO,and the formation mechanism of NiFe alloy was also revealed.In-situ FTIR and DFT calculation indicated that NiFe alloy enhanced the adsorption capacity of the catalyst.3.The carbon-supported catalysts usually show better catalytic activity than metal oxide supported catalysts due to their weaker MSI effect.However,this weak MSI effect will lead to poor catalytic stability.In this work,Ni particles were encapsulated into the cavity of hollow carbon sphere(HCS)to obtain the catalyst(Ni@HCS),which greatly enhanced the MSI effect between carbon support and the active metal due to the hollow structure of the catalyst,thus strengthening the stability of the catalyst.Besides,the void-confinement effect of the HCS also improved the selectivity of Ni@HCS,which can afford 99.1%cyclopentanone yield at 150℃.The reaction mechanism was studied by experiments combined with theoretical calculation,it was found that in this reaction water not only acted as solvent but also participated in the furan ring-opening rearrangement process and promoted the formation of cyclopentanone.4.The pyrolysis of metal organic complexes can in-situ produce catalysts with MSI effect between metal and carbon support through carbothermal process.The addition of heteroatoms in this process can further improve the MSI effect,which not only improve the stability of the catalyst but also provide new reactant adsorption sites to improve catalytic activity.Herein,the ionic liquid was applied as the precursor to synthesize Ni@NP-C catalyst,which is composed of high dispersed Ni nanoparticles and N,P co-doped carbon layer.Compared with the previous Ni@HCS catalyst,the activity of Ni@NP-C was significantly improved,which can achieve a high yield of cyclopentanone under milder conditions.XPS and TEM confirmed that the pyrolysis temperature can affect the MSI effect of the catalyst and the chemical state of heteroatoms,thus affecting the catalytic activity.The doped heteroatoms not only improved the activity but also improved the selectivity of the catalyst.To sum up,MSI effect plays an important role in the stability of heterogeneous catalysts.However,too strong MSI effect will inhibit the catalytic activity of active metals.In this thesis,a balance between MSI effect and catalytic activity was achieved by several methods,including adjusting the morphology of the support,constructing bimetallic alloy,using the void-confinement structure of carbon support and heteroatom doping.A variety of new catalysts with high activity,selectivity and stability were synthesized.This thesis provides new ideas and perspectives for the design and synthesis of efficient heterogeneous catalysts.