Studies On The Reactions And Catalysts For The Catalytic Wet Air Oxidation Of Organic Pollutants

The catalytic wet air oxidation (CWAO) is one of the economically and technologically most viable solutions for cleaning polluted water.In this thesis, three kinds of transition metal oxide catalysts were prepared, and their catalytic activities and stabilities of CWAO for model wastewater were also investigated. Two kinds of noble metal catalysts, the eggshell Ru/TiO2 and bimetallic Ru-Ce/TiO2, were specially prepared, and their catalytic activities and stabilities for CWAO of industrial wastewater were also evaluated. On the basis of the study on the Ru-Ce/TiO2 catalyst in laboratory, the pilot-plant-scale and plant-scale processes were conducted, respectively.Based on the property of variable oxidation states of cobalt, a Co-spinel mixed oxide was obtained by calcining the corresponding hydrotalcite-like precursor treated hydrothermally. The surface area of the resulting spinel mixed oxide without the amorphous CoO is measured to be 91 m2/g. After a CWAO of phenol on the above Co-spinel mixed oxide at 190°C and 2.5 MPa initial air pressure, the CODcr removal was 93 % and the leaching of Co was only 0.65 ppm.The FeMgxO1.5+x spinel mixed oxide was prepared by co-precipitation, which contains the oligomeric cluster of FexOy phase. The oligomeric cluster of FexOy and MgO in FeMgxO1.5+x can act as oxidation and basic centers, respectively. With the synergetic effect of the two centers, sulfonic salicylic acid can efficientlydecompose in both catalytic wet air oxidation process at 190°C with air as oxidant and catalytic oxidation process at 60°C with H2O2 as oxidant.The perovskite-type oxide LaxFeO1.5(1+x) was prepared with the hydroxyl acid-aided process. Salicylic acid and sulfonic salicylic acid with intramolecular H-bonding can be effectively removed at the lower temperature of 140°C on the La1.4FeO3.6 in CWAO. The addition of Zr is helpful for stabilizing of LaxFeO1.5(1+x) catalyst. The activity of La1.4FeZr0.56O4.72 is almost the same as that of La1.4FeO3.6, while its metal leaching can be further reduced to 20 %.In order to reduce Ru loading, the eggshell Ru/TiO2 catalyst was prepared by a twice incipient wetness impregnation. Eggshell Ru/TiO2 catalysts showed higher activity compared to the corresponding uniform catalysts with same Ru loading under the same reaction conditions.CWAO of some industrial wastewaters over the bimetallic Ru-Ce/ TiO2 catalyst was investigated, and the catalyst was also prepared by pilot-plant and plant scales, respectively. The reaction results for CWAO of both the H-acid model and coke-plant industrial wastewaters in the pilot-plant-scale equipment are as good as that in the lab-scale setup under same reaction conditions.