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Organically Functionalized Mesoporous Molecular Sieves Immobilize Metal Complexes: Design, Synthesis And Catalysis

Posted on:2005-12-26Degree:DoctorType:Dissertation
Country:ChinaCandidate:H Q YangFull Text:PDF
GTID:1101360125955776Subject:Physical chemistry
Abstract/Summary:PDF Full Text Request
Mesoporous molecular sieves with unique textural properties exhibits high potential applications and good prospects in chemical industry, environment protection, novel materials and even biological field,etc. As one important aspect of their applications, Mesoporous molecular sieves offer good opportunities and possibilities to heterogenization of the conventional homogeneous catalysts, which is widely regarded as an effective way to realize environment-friendly chemical process, and thus recently become one of hot topics in catalysis and organic synthesis.Beginning with synthesis of mesoporous sieves MCM-41 and HMS, a series of reactive organic groups or the groups with coordination functions were introduced into the channels of mesoporous molecular sieves, forming a series of organically functionalized mesoporous sieves. The metal complexes were immobilized on the organically functionalized mesoporous sieves through coordination, producing the developed the novel catalysts for Heck reaction and epoxidation reaction. As our studies showed, silylation of mesoporous molecular sieves with alkoxysilane was an usual method of linking desired organical groups. However ,as a result, the a lot of silanol groups still existed on the surface of mosoporous molecular sieves after silylation, which maybe affect the interface property and its catalystic activity. Based on this consideration, a novel method was proposed that a mixture of trichlorosilanes was used to silylate mesoporous molecular sieves, introducing both the further reactive group and hyhrophobic methyl group in one pot.Chapter one summarized the textual and surface properties of mesoporous sieves, summarized the major preparation methods, aspects of molecular design and applications of organically functionalized molecular sieves, reviewed the achievements of heterogenization of homogeneous catalysts, analyzed it advantages and disadvantages, simply expounded on the coming opportunities and possibilities for organically funtionalized mesoporous molecualar sieves, discussed the approaches of immobilization of homogeneous catalysts, reviewed and previewed their applications in catalysis and organic synthesis .Chapter two. The mesoporous molecular sieves MCM-41 and HMS were synthesized according to the reported references and characterized with XRD and N2 sorptiontechniques. The methods of synthesizing mesoporous silicas with relatively big size were also investigated.Chapter three . Dicyano-functionalized MCM-41 were synthesized via surface modification of chlorobenzyl and chloropropyl functionalized MCM-41.Palladium complexes were anchored on dicyano-functionalized MCM-41 through ligand exchange with Cl2Pd(C6H5CN)2. The introduction of dicyano groups enhanced the immobilizing activity towards Pd, and the relatively high dispersion was obtained after being reduced with NaBH4. The developed catalysts demonstrated good activities towards the Heck reaction of iodobenzene and methyl acrylate with about 90% yield, easy separation after reaction and reusability .The metal leaching was not apparent after four runs.BET, XRD, FT-IR, ICP-AES, H2 chemisorption as well as XPS analysis were employed to characterize the novel catalysts.Chapter four. Diamino & 2,4-pentadione-functionalized mesoporous molecular sieves were obtained by surface modfication of mesoporous HMS and chloropropyl-functionaled or chlorobenzyl-functionalied MCM-41, respectively. The homogeneous MoO(acac)2 and V(IV) species were heterogenized onto the organically functionalized mesoporous molecular sieves, resulting in the hybrid catalysts for alkene epoxidation. The developed catalysts, especially for HMS-aasp-Mo exhibited as high activity as homogeneous analogue for cyclohexene epoxidation , The selectivity was above 80% and the activity still reached 59% after five runs .Chapter five. As a novel method of immobilizing salen complexes, Co-salen complex was covalently anchored on MCM-41 through silylation of mesoporous material with alkoxysilane functionalized Co saleh complex, which was syn...
Keywords/Search Tags:mesoporous molecular sieves, organically functionalized, Heck reaction epoxidation, catalyst characterization
PDF Full Text Request
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