Controllable Synthesis And Catalytic Application Of ZIFs Derived Materials In The Selective Hydrogenation Of α, β-Unsaturated Aromatic Aldehydes/Acids

α,β-Unsaturated aromatic aldehydes/acids are a large number of natural compounds in nature.The compounds themselves and the selective hydrogenation products generally have a mild,lasting and comfortable aroma,elegant fragrance,and are widely used in the preparation of antibacterial drugs,anti-tumor drugs and HIV-1 protease inhibitors.Taking the selective hydrogenation of cinnamaldehyde（CAL）to cinnamyl alcohol（COL）as an example,the main difficulty of the reaction is that the bond energy of C=O bond(715 KJ·mol^-1)is greater than that of C=C(615 KJ·mol^-1),which leads to the difficulty in improving the selectivity of COL.Zeolite imidazole framework materials（ZIFs）are porous crystal materials composed of tetrahedral clusters of MN₄（M=Zn（II）,Co（II））,and are connected by simple imidazole ligands.ZIFs show significant potential in gas storage and eparation applications and catalytic chemical reactions.Because of its high thermal stability,ZIFs derived carbon materials have overcome the characteristics of metal particle migration,aggregation,sintering and leaching of many catalysts,and have attracted much attention due to their excellent performance in catalytic hydrogenation.Therefore,the study of ZIFs derived catalysts is significant for the selective catalytic hydrogenation of cinnamaldehyde/acid.In this paper,a variety of ZIFs were prepared by solvothermal method and their derived carbon materials were modified to synthesize Ni-containing N-doped carbon composites and bimetallic Pd/Ni and Co/Ni N-doped carbon composites with high catalytic activity and selectivity.The selective hydrogenation of theα,β-unsaturated aromatic compounds is the research content,and the heterogeneous catalytic reaction results of ZIF-derived catalysts in selective hydrogenation are studied.1.Using iron chloride,benzimidazole,and sodium formate as raw materials,Fe-ZIF was synthesized using a solvothermal method and used to prepare a derivative material Fe@CN.It was further prepared by adding Ni salts and urea,introducing Ni and N through ultrasonic assisted heating adsorption,and then preparing a bimetallic Ni₃/Fe@CN catalyst through H₂pyrolysis.The Ni₃/Fe@CN catalyst was used to catalyze the selective hydrogenation of cinnamaldehyde to cinnamyl alcohol at 140°C,94.3%conversion of cinnamaldehyde and86.3%selectivity of the cinnamyl alcohol were obtained.The reasons for the excellent catalytic performance of the material were investigated through XRD,FTIR,Raman,FESEM,TEM,TG,XPS,and H₂-TPR characterization.The introduction of metal Ni and urea was more conducive to the dispersion of Ni on the surface of the carrier,and it made the metal Ni and the carrier in the catalyst has a certain synergistic effect,so it exhibited good catalytic performance in the selective hydrogenation of cinnamaldehyde to cinnamyl alcohol.Subsequently,using nickel nitrate,benzimidazole,and sodium formate as raw materials,Ni-ZIF precursors were synthesized by a mixed solvothermal method,and then obtained by pyrolysis in N₂ atmosphere Ni@CN catalyzer.When applied to the catalytic selective hydrogenation of cinnamaldehyde to phenylpropanal,under reaction conditions of 100°C,2.0MPa H₂,and 4 h,the conversion up to 100%of cinnamaldehyde and the 100%selectivity of the product phenylpropanal can be obtained.Through a series of characterization of catalyst materials,the reasons for the excellent catalytic performance of the catalyst were explored.The material has a high metal Ni content and a large specific surface area,and the investigation of the circulation performance of the catalyst indicated that Ni@CN catalyst has excellent stability.2.The derived material Ni@CN was prepared by synthesizing Fe-ZIF in the hydrogenation system of cinnamaldehyde,and the catalyst Co/Ni@CN was prepared by introducing Co through impregnation and pyrolysis in H₂ atmosphere.It was used to catalyze the selective hydrogenation of cinnamic acid to phenylpropionic acid with a conversion of100%cinnamic acid and a selectivity of 100%phenylpropionic acid under reaction conditions of 50°C,3.0 MPa H₂,and 4 h.The reasons for the excellent catalytic performance of the material were investigated by XRD,FESEM,TEM,XPS,BET,WCA.The synergistic effect between the bimetallic compounds enhances the conversion of the reaction.Subsequently,Pd was introduced into carrier Ni@CN by impregnation method,and the catalyst 1‰Pd/Ni@CN was prepared by pyrolysis in H₂ atmosphere.It was applied to the catalytic selective hydrogenation of cinnamic acid,using water as a solvent,the selective hydrogenation of cinnamic acid was achieved under reaction conditions of 140°C,2.0 MPa H₂,and 5 h,100%selectivity of 3-cyclohexylpropionic acid was obtained.Under the reaction conditions of methanol as solvent,200°C,3.0 MPa H₂,and 12 h,the yield of 3-cyclohexylpropanol for the product of cinnamic acid total hydrogenation,could reach 90.1%.Through a series of characterization of catalyst materials,the reasons for the excellent catalytic performance of the materials were explored,one side Ni@CN The catalyst has a high metal Ni content and a large specific surface area and pore size,which improves its mass transfer efficiency.On the other hand,the doped Pd improves the selectivity of the target product by generating electronic coordination with Ni.