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The Preparation Of Ldh-salen Composite Materials And Their Application In N-oxidation Of Tertiary Amines

Posted on:2015-03-10Degree:MasterType:Thesis
Country:ChinaCandidate:J ZhangFull Text:PDF
GTID:2251330425984115Subject:Pharmaceutical Engineering
Abstract/Summary:PDF Full Text Request
The preparation of LDH-organic hybrid complex is an active area of academic and, more importantly, application research in the fields of electronics, photonics, magnetism and catalysis. In particular, as a superior catalyst, it has been proven to be effective in nearly all aspects of organic synthesis. Unfortunately, nearly no report about the application of LDH in the oxidation of tertiary amines has been published. The tertiary amine oxides are well-known for their valuable and practical effect in drug synthesis, oxidation of olefins, clinical therapy and catalyst preparation as intermediates. Thus, it’s not only broaden the applicational range of LDH but also possess industrial application value to prepare LDH-organic composite materials.The research was based on two main aspects. First of all, the LDH-salen composite material Cat.l was prepared via traditional ion exchange method and its structure and chemical composition were detected and confirmed by XRD、ICP-AES、 NMR、FTIR、SEM、UV and elemental analysis. The N-oxidation of4-picoline was taken as probe reaction. The optimal reaction conditions were determined via parallel experiment and the yield of4-picoline N-oxide was improved to84%.12different tertiary amines were introduced to test the general applicability of Cat.1, inferring that the Cat.l was more functional in N-oxidation of hydrophilic tertiary amines than hydrophobic ones. The substrates with electron-donating groups would more easily be N-oxidized. Based on current salen theory, we designed and prepared some catalysts with different salen molecular structures and chelating metal species and then using them to explore the catalytic mechanism. The results showed that the electronic effect of salen ligan played a vital role in determining the catalytic properties. The one with strong electron-donating groups would have8to12higher catalytic effect than those with weak electron-donating groups or electron-drawing groups. In addition, only the ligand chelated with Mn possessed the N-oxidation ability among the other metals as Cu, Cr, Fe and Co. The four steps’catalytic mechanism was proposed including:1) the forming of nitrogen-mental bond between subtrates and catalyst;2) the combination of reactive oxygen and Mn;3) the nucleophilic attack from N to O;4) removing one molecular water. Besides, some other catalysts like chitosan-salen porous material, Fe3O4@Salen magnetic material, W-Cs LDH,1%Au/C and TS-1were prepared and introduced, showing medium to excellent catalytic effect and providing new route to design this kind of catalysts. Finally, we did some scale-up experiment using2,3-dimethyl pyridine as substrate and the N-oxidation yield could reach97%. After catalyst resued for6times, the yield could still be maintained in95%, showing great industrial application potential.On the other hand, we successfully delaminated LDH incorporated with benzonate for the first time in our experiment. The single LDH nanosheet was detected and observed by AFM, TEM and DLS. We then demonstrated the successful direct assembly of LDH and Mn(II)-salen complex using a modied focculation process, thus providing a practical solution to introduce organic molecules into LDH galleries. The particles, when used as catalysts (Cat.4), showed remarkable catalytic properties and thermal stability over that prepared using a traditional ion exchange process. The yield of the oxidation of4-picoline to its N-oxide was over90%, even afer the catalyst was recycled6times. The reaction was both green and low cost, and the preparation was simple, thus offering an effective strategy for industrial production.
Keywords/Search Tags:LDH, Salen complex, tertiary amine, N-oxidation, sandwitch structure, nano material
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