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Preparation Of Expanded Graphite Load Cuo_x Catalyst And Molecular Oxygen Oxidation Of Ring-hexene Catalytic Performance Study

Posted on:2012-11-29Degree:MasterType:Thesis
Country:ChinaCandidate:R R ZhangFull Text:PDF
GTID:2191330335489076Subject:Organic Chemistry
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2-cyclohexene-l-one and its derivatives are very important Chemical intermediates in the manufacture of high-value fine chemicals, agrochemicals and pharmaceuticals. In traditional production process, 2-cyclohexene-1-one is prepared by oxidation of cyclohexene with chromic acid. There are many problems concerning low yield, catalyst lost, harsh condition, and serious pollution. Consequently, the development of oxidation reaction using molecular oxygen as a cheap, environmentally clean and convenient oxidant has attracted significant attention. Unfortunately, it was observed that the oxidation efficiency of molecular oxygen was poorer than other oxidants. Therefore, it is the key challenge to find effective catalysts for activation of molecular oxygen in developing new procedures using O2 as a green oxidant. Herein, with the aim to developing novel and more efficient catalyst, the research works below have been done:(1) Flake graphite supported CuOx catalyst (Cu/FG) is prepared and characterized by SEM, TEM and XRD, and applied to the oxidation of cyclohexene with molecular oxygen.2-cyclohexene-1-one and 2-cyclohexene-ol are got as the main products by ally lic oxidation. The influence of a series of different conditions for the reaction is also investigated. To a solution of cyclohexene (0.02 mol) in acetone (20 mL) in a three-necked flask equipped reflux condenser was added Cu/FG(1 wt%based on cyclohexene), the mixture was heated to 60℃and stirred for 12 h under 1 atm O2. The reaction conversion rate is 45.8%, and the total selectivity of allylic oxidation products is more than 90%, in particular, the selectivity of 2-cyclohexene-1-one could reach 49.7%.(2) Expanded graphite (EG) is prepared from FG by chemical oxidation. EG supported CuOx nano-catalysts (Cu/EG) is prepared and applied to the oxidation of cyclohexene reaction. Cu/EG shows superior catalytic activity to Cu/FG. The conversion of cyclohexene can be over 70%, the selectivity of 2-cyclohexene-l-one can be reached 61.8%. Furthermore, in order to explore the reasons, the catalysts are characterized by SEM and the corresponding EDAX, XRD, FT-IR, ICP and N2 adsorption and desorption, etc. Experimental results show the surface area of carriers can be increased by the chemical oxidation, and EG formed-OH, C=O, C-O-C and other functional groups on the surface; Meanwhile, Fe and Mn elements are also introduced into EG, which increase the multiple catalytic active center.(3) A novel cross-shaped Cu/EG is prepared by intermittent feeding method. This kind of catalyst showed better catalytic activity:conversion of cyclohexene can be more the 90%. In the optimum conditions, the conversion and the selectivity of 2-cyclohexene-l-one are 98.2% and 62.1%respectively. Such catalysts can be reused 3 times with high activity. Based on the experimental results and the literatures, the possible reaction mechanism is proposed.(4) EG1, EG2 and EG3 are prepared by changing the amount of FeCl3 and KMnO4 in the chemical oxidation. Then Cu/EG1, Cu/EG2 and Cu/EG3 are prepared by intermittent feeding. Cu/EG3 shows the best catalytic effect:the conversion of cyclohexene is 98.9%, and the selectivity of 2-cyclohexene-l-one is 71.3%. Furthermore, Bi, Co and Ni are doped into Cu/EG3 respectively. Among these catalysts, Bi-doping Cu/EG3 shows the best catalytic activity:the conversion of cyclohexene is 100%, and the selectivity of 2-cyclohexene-l-one is 78.9%. The supported catalyst can be reused for 4 times with high conversion (88.3%) and selectivity (73.2%).
Keywords/Search Tags:allylic oxidation, cyclohexene, molecular oxygen, expanded graphite supported CuO_x catalyst, 2-cyclohexene-1-one
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