Surface properties of CeO2-TiO2 catalyst and its catalytic activity in wet air oxidation

CeO2-TiO2 catalysts were prepared by sol-gel and coprecipitation methods. The physical properties including surface area, metal crystal phases, surface components, and pH(PZC) of the catalysts were characterized by N-2 adsorption, X-ray diffraction, transmission electron microscopy, X-ray photoelectron spectroscopy, and Zeta potentiometric analysis. The catalytic activity for wet air oxidation (WAO) of high concentration acetic acid and phenol was investigated. Moreover, the relationship between the surface structure and the catalytic activity was studied. The results showed that for the CeO2-TiO2 catalysts, the increase in the specific surface area and the decrease in the particle size are due to the interaction of Ce and Ti. A higher content of the chemisorbed oxygen was present on the surface of the CeO2-TiO2 catalysts. The pH(PZC) of the CeO2-TiO2-2 catalyst (pH(PZC) = 4.6) prepared by coprecipitation was higher than that of the CeO2-TiO2-1 catalyst (pH(PZC) = 3.2) prepared by the sol-gel method. The adsorption of acetic acid and phenol on the surface of CeO2-TiO2-2 is more effective. In WAO of acetic acid and phenol, the CeO2-TiO2 catalysts were very active. The activity of CeO2-TiO2-2 was the highest. By using the CeO2-TiO2-2 catalyst, about 79% COD removal was obtained in WAO of acetic acid at 230 degrees C and 5 MPa after 120 min reaction, while about 96% COD removal was achieved in WAO of phenol at 150 degrees C and 4 MPa after 120 min reaction.