| Photocatalytic technology can oxidate organic compounds selectively in mild experimental conditions. Therefore, in recent years, the development and application of light catalysts with high catalytic activity and high selectivity is a hot topic of photocatalytic technology research in organic synthesis. The oxidation products of cyclohexene and cyclohexane are very important chemical intermediates, hence, it is extremely significant to realize the selective oxidation of cyclohexene and cyclohexane in mild experimental conditions. This thesis is focused on the study about the oxidation degradation of methyl orange and selective oxidation of cyclohexene and cyclohexane with molecular oxygen catalyzed by a series of semiconductor oxide catalysts under visible light irradiation, and the major works are summarized as follows:(1) A series of Cu2O catalysts were prepared by hydrothermal method(HM) and adding surfactant method(SM) using copper acetate as raw material. Then the obtained catalysts were characterized by nitrogen adsorption-desorption, UV-Vis, XRD and TEM, the results showed that the obtained catalysts exhibited broad visible light absorption, surface area is very small, particle size was about800nm, and the morphology of Cu2O(HM) and Cu2O(SM) were cotton-like and spherical respectively. And their photocatalytic performances evaluated with the oxidative degradation of methyl orange under visible light. These semiconductor oxides were found to be active to this degradation reaction, in the optimal reaction conditions,25mg of Cu2O(HM-5t) prepared though hydrothermal reaction for5h could gave96.7%degradation rate of methyl orange after irradiating for3h with a35W halogen lamp. While The photocatalytic performance of Cu2O(SM) was better,98.6%of degradation rate was obtained upon only10mg of Cu2O(SM) catalyst under the same reaction conditions.(2) In order to obtain catalysts with better photocatalytic performance, CuO/TiO2and CuO-TiO2composite oxides were prepared by an adsorption method and coprecipitation method respectively. Then characterized by nitrogen adsorption-desorption, UV-Vis, XRD and TEM. The results showed that both of CuO/TiO2and CuO-TiO2exhibited broad visible light absorption, their surface area were20.3m2/g and17.1m2/g respectively, particle size was about30-40nm, and the morphology of CuO/TiO2and CuO-TiO2were not neat. The selective oxidation of cyclohexene and cyclohexane with molecular oxygen in water-acetone media was employed to assess the photocatalytic performance of these catalysts and the promoted role of metal complexes was studied under halogen lamp irradiation in the small self-assembly photo-reactor. The results showed that, cyclohexene could be oxidized to cyclohexenol, cyclohexenone and a small of epoxycyclohexane, but its conversion was very low when only using these semiconductor oxides as catalysts; while the photocatalytic activity of CuO/TiO2and CuO-TiO2catalysts were promoted to a certain degree. Notably, after adding some metal complexes to the photoreaction system, the conversion increased significantly, especially for CuO/TiO2and CuO-TiO2catalysts. For example, the addition of5,7-dibromo-8-Quinolinolato Manganese Complex (Q3Mnm) resulted in an significant increase in cyclohexene conversion from2.8to20.8%. At the same time, it was found that the oxidation of cyclohexane by molecular oxygen hardly occurred in this photocatalytic system. What’s more, a reasonable reaction mechanism for the present photocatalysis was proposed.(3) On the basis of the reaction system described above, CuO-TiO2and Q3MnⅢ co-photocatalyzed oxidation of cylcohexene with dioxygen was investigated in details. Firstly, the effect of preparation conditions of CuO-TiO2catalyst on photocatalytic oxidation of cyclohexene were investigated, such as concentration of NaOH、calcining temperature and the mass ratio of copper and titanium, the results showed that the photocatalytic performance of CuO-TiO2catalyst was the best when concentration of NaOH was1mol/L, the calcining temperature was600℃, the mass ratio of copper and titanium was1:1; Secondly, the effect of different manganese source and different8-hydroxyquinoline ligands on photocatalytic oxidation of cyclohexene were investigated, the results showed that the promoting effect of manganese metal complexes was much better than that of manganese inorganic salts, and the promoting effect of8-hydroxyquinoline manganese metal complexes with substituents was obvious better; At last, it was with focus on the effect of various parameters on this photocatalytic reaction, which included reaction temperature and time, solvents and so on. Under the optimum reaction conditions, the conversion of cyclohexene was32.2%, providing cyclohexenone(60.6%), cyclohexenol(35.7%) and epoxycyclohexane (3.7%) as oxidative products. |
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