Synthesis And Catalytic Properties Of Bimetallic Porous Silicate Materials

In the past decades,the prominent hot issues such as energy crisis and environmental degradation,have brought new requirements and challenges to chemical production,requiring researchers to make more efforts to improve the stability and efficiency of catalysts.Due to the advantages of long-term effectiveness and recoverability,heterogeneous metal catalysts play a pivotal role in practical applications and have become the major center of research focus.In this thesis,a series of porous metal silicate（PMS）materials for stabilizing bimetallic active sites are developed on the basis of the methods of stabilizing metal active sites in zeolites,metal-organic framework materials and other methods for stabilizing metal active sites.The characterizations and catalytic properties of PMS materials are studied by a series of spectral tests and model reactions.The main research contents are as follows:（1）A bimetallic PMS material,denoted as PMS-12,is synthesized by sol-gel method in the presence of Cu and V bimetal–organic complex as the template,and subsequent calcination under a nitrogen atmosphere.PMS-12 demonstrates high activity in the aerobic oxidation of phenol,which could initiate the aerobic oxidation at30 ^oC under an atmosphere of 1.0 MPa O₂,and phenol can be almost completely converted to benzoquinone at 60 ^oC.The characterization results show that the electron transfer and synergistic effect between the Cu and V active sites in PMS-12 are the key factors to achieve high efficiently catalytic aerobic oxidation of phenol.PMS-12 could also prompt aerobic oxidation of a wide range of phenolic reactants under low oxygen pressure,which is even much superior to the noble metal catalysts in the literature.（2）A PMS material,denoted as PMS-20,is synthesized by sol-gel method in the presence of Cu-2-picolinate complex as the template and aluminum trichloride as the aluminum source,and subsequent calcination in an air atmosphere and reduction in an H₂/Ar atmosphere.The application of PMS-20 in upgrading of furfural to 2-methylfuran as a fuel component is studied.Almost complete conversion of furfural to the target product is achieved under mild reaction conditions of 160 ^oC and 1.5 MPa H₂.The pore confinement effect and the interaction between Cu sites and acidic sites highly improve the stability of PMS-20 in catalysis,inhibiting the migration and aggregation of metal sites during heat treatment and reaction processes.A series of characterization results show that acidic sites could affect the electronic state of Cu active sites,and the catalytic activity of PMS-20 and the selectivity of target products can be optimized by regulating the content of acid sites in the material.（3）A PMS material,denoted as PMS-36,is fabricated by using Ni-2-picolinate complex as the template in the presence of aluminum trichloride as the aluminum source via sol-gel synthesis method,and subsequent calcination under an air atmosphere and reduction in a mixed gas atmosphere of H₂ and Ar.The pore confinement effect and acidic sites highly improve the anti-sintering ability of Ni sites,greatly improving the stability and activity in catalysis.The application of PMS-36 in upgrading of lignin-derived phenolic compounds to saturated naphthenes is studied by catalyzing a model reaction of guaiacol hydrodeoxygenation reaction.The electronic environment of Ni sites in PMS-36 and the product distribution of the model reaction are systematically tunable by adjusting the content of acidic sites.Guaiacol can be almost completely converted to cyclohexane at 200 ^oC and 2.0 MPa H₂.PMS-36 also demonstrates high efficiency and selectivity in catalyzing a series of hydrodeoxygenation reactions with desired catalytic results by using different lignin-derived phenolic compounds as the substrates,which is much superior to the non-noble metal catalysts in the literature.