Preparation Of Mesoporous Composite Metal Oxides And Catalytic Selective Oxidation Reactions

Composite metal oxides made from cheap metals are welcomed by researchers because of their adjustable electronic band structure,wide range of oxidation performance,low cost and simple preparation.How to improve the specific surface area of the catalyst and thus enhance the active site of the catalyst is a key to breaking through the performance of the catalyst.In this thesis,mesoporous metal oxides MnCo₂O_4.5 and NiCo₂O₄ were prepared by using mesoporous silica as template and solvent-free continuous filling method,and applied to the catalytic synthesis of 1,5-diketone and poly-substituted imidazole.The main research contents are as follows:（1）Using ordered mesoporous material KIT-6 as a template,metal oxides MnCo₂O_4.5 and NiCo₂O₄ with high exposure,high specific surface area and special pore structure were prepared by continuous filling method.In this method,the nitrate containing crystal water is heated,melted and continuously filled into the template in batches,which overcomes the problem of the limited amount of metal salts that can be dissolved by the solvent,and greatly improves the utilization rate of the template.The composition elements and morphology of mesoporous MnCo₂O_4.5 and NiCo₂O₄ were further confirmed by XRD,XPS,TEM,SEM,HRTEM,and SAED characterization methods,demonstrating that the material has a highly ordered nanosieve structure.Due to the Jahn-Teller effect of different metal ions in the composite metal oxide,the material has the unique advantages of the multi-valence change of ions and the synergistic effect of high electronic capacity,thus improving the performance of the catalyst.（2）Application of mesoporous MnCo₂O_4.5 catalyst in the synthesis of 1,5-diketone from substituted benzyl alcohol and acetophenone in series.It was found that in the presence of catalyst,the benzaldehyde obtained from the oxidation of benzyl alcohol and acetophenone underwent 1,2-addition,elimination and 1,4-addition reactions successively under alkaline conditions,and the 1,5-dicarbonyl compound was successfully prepared,with a yield of 88%.It is worth mentioning that the benzaldehyde prepared by reaction catalysis can just drive the series reaction and make the reaction go smoothly.If benzaldehyde is directly used as the raw material,the reaction yield will be greatly reduced due to the production large amount of chalcone.According to the reaction results,it is found that the reaction is universal,and the target products with higher yields can be obtained from benzyl alcohol and acetophenone substituted by electron acceptor or electron donor.（3）Nano mesoporous NiCo₂O₄ material was used to catalyze the formation of polysubstituted imidazole compounds from diphenylethanone,benzaldehyde,aniline and ammonium acetate in series,with high yield.According to the experimental results,mesoporous NiCo₂O₄ plays a role in activating the reaction substrate and oxidizing the intermediate of diphenylethanone in the reaction.Benzaldehyde,aniline,and ammonium acetate are continuously connected in series to obtain a diamine intermediate,which is then subjected to nucleophilic addition with diphenylethanone,followed by oxidation and nucleophilic addition under catalyst catalysis,and then undergoes intramolecular dehydration and aromatization to obtain polysubstituted imidazole derivatives.Further research on the feasibility of various aldehydes and amine derivatives showed that the reaction had good universality,mild reaction conditions,and was environmentally friendly.