Preparation And Characterization Of Low Cerium Content Rare Earth Oxygen Storage Material

Recently, more and more attention has been paid to the purification of automobile exhaust. The application of three way catalysts (TWC) can effectively get rid of the harmful hydrocarbon (HC), nitrogen oxides (NO_X) and carbon monoxide. As the key components and supports of the TWCs, Oxygen storage materials' textural properties, oxygen storage capacity and their thermal stabilities have' great effects on the performance of the catalyst. Now, the thermal stability of materials' oxygen storage capacity (OSC) has been improved greatly, but its textural properties, especially after being aged at high temperature, are still dissatisfying.In this dissertation, a series of high specific surface area, large pore volume and low Ce content OSMs were precipitated with mixed ammonia-ammonium carbonate solution, and assisted by PEG and PVA. Concentrated ammonia aqueous solution, ammonium carbonate solution and mixed ammonia-ammonium carbonate solution were used as precipitator to prepare OSM with different composition, their properties were studied. A detailed investigation was carried on the effects of preparation condition on the propertiesof OSM with composition of Ceo.15Zro.75Yo.10O2. After being treated at different temperature, the samples' textural properties, oxygen storage capacities, phase composition, and redox behavior were researched with BET, oxygen pulse adsorption, X-ray diffraction (XRD) and H2-temperature programmed reduction (H2-TPR) techniques.The results indicate that OSMs precipitated with concentrated ammonia solution showed superior OSC; and materials prepared with ammonium carbonate solution have a large specific surface area before aged. After being aged at 1000 °C, OSMs prepared with mixed precipitator exhibit excellent thermal stability of their textural properties and oxygen storage capacities. Especially, the material with the composition of Ceo.15Zro.75Yo.10O2 showed the best thermal stability of textural property and oxygen storage capacity. With the addition of polymers, a relatively higher precipitation temperature and more concentrated reactant mixed solution can improve the materials textural properties, oxygen storage capacities, and their thermal stabilities. Furthermore, treatinging at high temperature and long time will benefit to the formation of big pores, this can improve the materials thermal stability. The addition of appropriate amount of PEG and PVA before spray drying can improve the thermal stabilities of materials' textural properties.