| Oxidation of cyclohexane constitutes one of the most promising and challenging reactions due to the large demand for its oxidized products such as cyclohexanone and cyclohexanol, which are important raw materials for the production of adipic acid and caprolactam.Polyoxometalates could be useful catalysts for oxidation of various organic substrates with hydrogen peroxide or molecule oxygen. The catalytic function of polyoxometalates has attracted much attention because their acidic and redox properties can be controlled at atomic or molecular levels. That is, when some metal atoms of heterpoly anion are substituted for other metal atom, the framewoke of the heteropoly anion is often still maintained, but its physical and chemical properties are substantially changed and often have specific catalytic function.In this paper, a series of Keggin type and Dawson type vanadium-substituted heteropolyanions were prepared successfully and characterized by IR, UV, DTA-TGA and cyclic voltammetry to study the oxidition-reduction beheviour and spectroscopic features. The catalyst showed excellent activity for the oxidation of cyclohexane with hydrogen peroxide as oxidant. We discussed the relationship between the activity and reaction condition. The mechanism of the oxidation over Vanadium-substituted heteropoly compounds was studied exploringly. We also synthesized a series of transition metal substituted heteropolytungstate compound and studied their oxidition-reduction beheviour detailedly in the mixed solvents of water-dioxane for the first time and those catalysts might be promising catalysts.1. Some Vanadium-contained compounds were prepared and characterized. We investigated their activity on the oxidation of cyclohexane and the decomposition of H2O2 and found that the coordinate surrounding of Vanadium effect the activity of reaction strongly. When we use vanadium-substituted heteropoly compounds as catalyst, the decomposition of H2O2 can be restrained. Especially when vanadium was on the coordination site, such as H4PMo11V1O40, the catalyst showed excellent activity for the oxidation of cyclohexane with low speed of the decomposition of H2O2.2. A series of Keggin type vanadium-substituted heteropolyanions PMo12-nVn (n=1~3) were prepared and studied how the reaction condition effect the oxidation of cyclohexane. The oxidation of cyclohexane with hydrogen peroxide did not proceed when we use Keggin type molybdophosporic heteropolyacid as catalyst. But the vanadium-substituted heteropolyanion catalyst showed excellent catalytic behaviors in the oxidation of cyclohexane and their catalytic activity was increased with the increment of the number of the vanadium atom in heteropoly anions. The main products were cyclohexanone, cyclohexanol and cyclohexyl hydroperoxide when using acetonitrile as solvent. The best result was obtained when the amount of the catalyst was 0.04~0.06g and temperatures was 60 (C and the amount of H2O2 was 19.1mmol. In addition, cyclohexanol is the mostly product when the amount of H2O2 was deficient. There was more cyclohexanone in products with the increment of amount of H2O2.At the beginning of the reaction the conversion of cyclohexane increased more rapid and became slow after 4~6 hour. At the beginning of the reaction did not identify the formation of cyclohexanone, only cyclohexanol and cyclohexyl hydroperoxide in the reaction solution. Amount of cyclohexyl hydroperoxide increaced along with the process of reaction, and then reduced. But the amount of cyclohexanone increaced at all times. Based upon the above discussions, it can be assumed that there was the decomposition of cyclohexyl hydroperoxide in the reaction and the formation of cyclohexanone might be the further oxidation of cyclohexanol or the decomposition of cyclohexyl hydroperoxide.3. A series of transition metal substituted molybdovanadophosphoric heteropoly compounds H3Na5PMo10VMO40·nH2O (M=Zn, Fe, Mn, Co, Ni, Cu) were prepared one step and characterized by ICP, IR, UV, DTA-TGA and cyclic voltammetr...
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