| Ceria-zirconia-alumina composite oxide is an important component in three way catalyst as oxygen storage material. It has replaced the mixture of ceria-zirconia solid solution and alumina to enhance the thermal stability. Ceria-zirconia-alumina composite oxide was prepared by precipitating cerium and zirconium simultaneously on the surface of alumina with pseudo boehmite as starting alumina source, cerium nitrate and zirconium nitrate as raw materials, hydrogen peroxide as oxidant and ammonia as precipitant.Effects of hydrogen peroxide, precipitants and alumina content were studied on the performance of ceria-zirconia-alumina composite oxide. Results showed that the optimized process was adding H2O2(1.2molar amount of Ce) before precipitating to oxidize Ce3+, adopting ammonia as precipitant to pH=10and alumina mass fraction is60%. Under this condition, effect of different solid alumina sources (pseudo boehmite, activated alumina, modified alumina) was studied. Results showed that ceria-zirconia-alumina composite oxide with pseudo boehmite as alumina source had the largest BET surface area while the sample with modified alumina as alumina source exhibited better aging resistance property and oxygen storage capacity.Different surfactants before precipitating and treatments on precursor were also studied on the performance of ceria-zirconia-alumina composite oxide. Results showed that cationic surfactant CTAB performed better than anionic surfactant SDS and non-ionic surfactant TW80with optimized adding amount of30wt%. The best aging temperature and time for precursor were70℃and2h. Different treatments (untreated, drying, adding dispersant) were made to the filter cake to explore the effect of dehydrating process of precursor on the performance of ceria-zirconia-alumina composite oxide. Results showed that the sample with filter cake dispersed exhibited better performance on surface and redox properties with high oxygen storage capacity. |
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