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Epoxidation Of Cyclohexene With Oxygen Basing On Zeolitic And Mesostructured Catalysts

Posted on:2010-01-07Degree:MasterType:Thesis
Country:ChinaCandidate:J SongFull Text:PDF
GTID:2131330338982312Subject:Chemical Engineering and Technology
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The catalytic epoxidation of cyclohexene by molecular oxygen in a heterogeneous system is one of the most attractive topics in the field of catalysis chemistry, so it has been being paid much attention from both scientific and industrial domains. At present, the industrial production of cyclohexene oxide is H2O2 method, in which H2O2 is expensive and there may be explosive hidden trouble. Therefore, it is meaningful in using cheap and clean molecular oxygen as oxidant because of its importance in academy and economy. The current catalysts reported in molecular oxygen method are divided into two parts. One is homogeneous catalyst, which is hard to separate and recycle; the other is heterogeneous catalyst, which is mainly supported by metal complexes and polynuclear metal complexes. However, some problems still exist, for example, complex preparation process, high price and easy to lose active components. What's more, the aldehyde used as co-reductant in the reaction is expensive. For example, catalytic epoxidation of cyclohexene with molecular oxygen was studied by R. Krishnan, in the presence of butyraldehyde using polynuclear manganese complexes, in which the conversion of cyclohexene is 63%, and the selectivity of cyclohexene oxide is 91%. The objective of cyclohexene epoxidation is to design the excellent catalyst, which is easy to separate and recycle, and activate molecular oxygen.In the present work, a series of catalysts containing transition metals are synthesized with different methods and characterized by XRD, FT-IR. The series of catalysts we prepared are SBA-15,MCM-41,TS-1,Y,ZSM-5 zeolites and AlPO intermingling transition metals. The modified SBA-15, MCM-41 mesoporous materials and TS-1 are synthesized by in situ method. The modified Y and ZSM-5 zeolites are prepared by impregnated or ion-exchanged method. Metal phosphor-aluminate catalysts are prepared by citric acid method and solid phase method, respectively.In this paper, the catalysts are used for the epoxidation of cyclohexene. Catalytic epoxidation of cyclohexene using CH3CN as solvent, benzaldehyde as reductant and molecular oxygen as oxygen source over these catalysts is studied. The effects of reaction factors, such as the molar ratio of aldehyde/cyclohexene, the amount of catalyst, reaction temperature and reaction time, are investigated over Ti-SBA-15 catalyst.Among all of the catalysts, La-SBA-15 shows the best catalytic activity for the epoxidation of cyclohexene, the yield of cyclohexene oxide is 62.01%. Secondly, Cu-MCM-41, Ni-TS-1, Cu/Y, LaAlPO and LaCuAlPO show the yield of cyclohexene oxide more than 50%.In conclusion, a series of novel catalysts, namely modified mesoporous materials and zeolites are synthesized and used for the epoxidation of cyclohexene, and there isn't any reported literature yet. For these catalyst systems, the catalysts have many advantages, such as good catalytic performance, easy to separate and long anticipating life. Moreover, the price of benzaldehyde as reductant compared with other aldehyde, such as n-butyraldehydel, isobutylaldehyde and neovaleraldehyde, is much lower. The catalytic data show that these catalysts are very active in the catalytic epoxidation of cyclohexene. The conversion of cyclohexene and the selectivity of objective production cyclohexene oxide have preferable result. Therefore, they have shown favorable development prospects in catalytic epoxidation of cyclohexene with molecular oxygen, and further research work should be done.
Keywords/Search Tags:Cyclohexene, Epoxidation, Zeolites, Mesoporous materials
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