Preparation of CeO2-ZrO2 mixed oxides with high thermal stability and their oxygen storage/release capacities
CeO2-ZrO2 mixed oxides are considered as one of the key components in the three-way catalysts for automotive exhaust purification.The increasingly strict emission regulations have brought much higher requitements regarding the thermal stability of CeO2-ZrO2 mixed oxides.In this work,CeO2-ZrO2 with excellent thermal stability were synthesized through co-precipitation method.The effect of synthesizing parameters including doping element,precursors,washing methods as well as ageing conditions on the specific surface area and thermal stability of the CeO2-ZrO2 samples were investigated.Results shown that CeO2/ZrO2/La2O3/Y2O3/Nd2O3(CZLYN)samples prepared by using La-Y-Nd co-doping as the modi-fied component,Ce(NH4)2(NO3)6 containing Ce4+as the cerium precursor,washed with ethanol and aged in an ethanol environment for 12 h exhibited the optimal specific surface area and thermal stability.The specific surface can still maintain at 38 m2·g-1 after 12 h thermal ageing at 1 050 ℃ using muffle furnace.The optimized CZLYN sample was further characterized and compared with one of the commercial CeO2-ZrO2 powder.Results showed that these two samples presented similar physical structure,grain size,pore size distribution and surface micro-morphology while the specific surface area of the optimized CZLYN sample was increased by about 60％.After thermal ageing at 1 050 ° using muffle furnace,the optimized CZLYN sample presented about 20％increase in the specific surface area of compared to the commercial CeO2-ZrO2 powder;after hydrothermal ageing,the optimized CZLYN samples still showed slightly higher specific surface area and about 30％increase in dynamic ox oxygen storage/release capacity,indicating its superior thermal stability.
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