Preparation Of Ce_0.5Zr_0.5O₂ Nano-Support In Rotor-Stator Reactor

CO is a common air pollutant that is seriously harmful to human’s health. At present, supported noble metal catalysts are widely used as an effective way to eliminate the CO in the air. The catalytic activity of catalysts is closely related to the structure and properties of supports. The cerium-zirconium oxides are attractive supports owing to its good oxygen storage performance. Nanosized cerium-zirconium oxide can effectively improve the dispersion of noble metal and activity of catalysts. Higee technology, which can improve the mass transfer and micromixing efficiency because of its unique intensification mechanism, has a good application on preparing nanoparticles with high surface area and uniform dispersion.In this study, Ce0.5Zr0.5O2 nanosupports were synthesized by the gas-liquid method and double reverse microemulsion method respectively in a rotor-stator reactor (RSR) by taking advantage of Higee technology. The effects of experimental conditions on the properties of the nanosuppots were investigated, including the initial reactant concentration, reaction temperature, RSR rotating speed et al. And the optimum conditions for preparing the Ce0.5Zr0.5O2 nanosupports with high surface area were determined. XRD, XPS, HRTEM, BET, N2-adsorption and desorption analyses were employed to characterize the Ce0.5Zr0.5O2 nanosupports.The results show that the Ce0.5Zr0.5O2 nanosupports prepared by the two methods were a tetragonal phase. In gas-liquid method, the optimum conditions were determined as reaction temperature of 50℃, initial reactant concentration of 0.05 mol·L-1, RSR speed of 800 r-min-1 and reaction end point pH of 9, and nanosupports were obtained with the specific surface area of 104.7 m2·g-1, average particle diameter of 7.4 nm and particle size distribution of 4-10 nm. In double reverse microemulsion method, the optimum conditions were determined as reaction temperature of 30℃, initial reactant concentration of 0.5 mol·L-1, RSR speed of 600 r·min-1 and liquid volumetric flow rate of 15 L·h-1, and nanosupports were obtained with the specific surface area of 122.5 m2·g-1, average particle diameter of 5.4 nm and particle size distribution of 4-7 nm.Compared with the conventional stirring reactor, nanosupports with better crystallinity and larger surface area were obtained in the RSR, which shows a higher quality. Finally, Au/Ce0.5Zr00.5O2 catalysts were prepared by impregnation method and the activity of the catalysts were determined by CO oxidation. It is evidenced that CO was converted to CO2 at 120℃ and 110℃ for 95% with the catalysts whose supports were prepared by the gas-liquid method and double reverse microemulsion method, respectively.