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Preparation, Characterization Of NaY Zeolite Encapsulated CoSalen Complex And Its Catalytic Performance

Posted on:2008-12-22Degree:MasterType:Thesis
Country:ChinaCandidate:F LiFull Text:PDF
GTID:2121360218457819Subject:Chemical Engineering
Abstract/Summary:PDF Full Text Request
N,N'-Bis (salicylidene)ethylenediiminocobalt (Cosalen) is widely used in the catalytic oxidation reaction with ability to activate oxygen efficiency. However, the Cobalt Schiff base complex is easily deactivated due to the formation ofμ-oxo-dimers and simple dimmers, Immobilizing the complex on microprous solids is considered to be an effective way to improve its stability.In this paper, Cobalt Schiff base complex was encapsulated in the supercage of NaY zeolite by the technique of"ship-in a-bottle". Firstly, the Co exchanged NaY zeolite (CoNaY) was prepared by treating dehydrated zeolite with Co(OAC)2.4H2O solution. then the complex between the CoNaY and salen ligand could be realized in the t-butyl alcohol solution under reflux temperature, after treating with the Soxhlet extraction, NaCl solution reflux, CoSalen/Y(SB)was obtained. At the same time, the impregnated Cosalen immobilized on the external surface of the zeolite was also prepared to compare with the encapsulated complex. The formed zeolite-encapsulated catalyst was characterized by FT-IR, DRS, XRD, TG/DTA and SEM. The results of FT-IR,DRS indicated the existence of CoSalen in zeolite, XRD and SEM'results proved that CoSalen had entered cavities of NaY zeolite successfully with no harm to crystalloid of zeolite, moreover, the results of TG/DTA showed that the sequence of heat stability was SB>IM>CoSalen. CoSalen/Y(SB) showed better catalytic activity in oxidation of cyclohexane byoxygen compared with CoSalen complex and CoSalen/Y(IM). The solvent effect was existed in the oxidation reaction catalyzed by the Cosalen/Y(SB). The conversion of cyclohexane was up to 25% used acetonitrile as solvent at 130℃for 3h under 0.85 MPa oxygen pressure in the presence of CoSalen/Y(SB), and the total selectivity of cyclohexanol, cyclohexanone and adpic acid was relatively high. The effect of reaction temperature, reaction time, initial oxygen pressure, oxygen source were also investigated. Among the products, the amount of cyclohexylhydroperoxide (CHHP) was small, it showed that the Cosalen/Y (SB) had the ability to add the decompose of the CHHP. Initial oxygen pressure was the important factor effected the reaction. With increasing oxygen pressure, the conversion of cyclohexane was improverd and in favor of the production of cyclohexone, the ratio of cyclohexone to cyclohexol was also improved. The oxidation reaction could proceed effectively when the usage of catalyst was 0.5% of the adding amount of cyclohexane. The amount of acid in the products was found to observably increase with increasing reaction time, Cosalen/Y (SB) showed the ability to oxidize cyclohexane into acid by one step. Four times reuse experiments showed that the catalyst can be used repeatedly with no obvious loss of reactivity.
Keywords/Search Tags:NaY zeolite, CoSalen, cyclohexane oxidation, molecular oxygen
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