H_2O_2氧化对铈锆复合氧化物性能的影响研究

Effect of Peroxide Oxidation Time on the Properties of Cerium Zirconium Composite Oxide

以廉价白云石为原料所制备的碳酸氢镁溶液作为沉淀剂合成铈锆复合氧化物,研究沉淀过程中双氧水氧化稀土锆混合料液对铈锆复合氧化物性能的影响。采用XRD、BET、SEM、TPR、O2脉冲化学吸附技术等手段研究了不同氧化时间对铈锆复合氧化物的晶型、比表面积、微观形貌、氧化还原性质和储放氧能力的影响。结果表明:双氧水氧化稀土锆料液不仅可以有效提高铈锆复合氧化物的比表面和高温稳定性,抑制其发生分相,而且可以提高铈锆复合氧化物表面活性氧的数量。随着氧化时间的延长,铈锆复合氧化物的比表面积、老化性能及储氧量增加,氧化时间为30 min时达到最佳效果,其600℃焙烧新鲜比表面积为111.3 m2/g,1000℃老化比表面积为32.9 m2/g,500℃时储氧量为315μmol O2/g;继续延长氧化时间,比表面积、老化性能及储氧量变化不大。

CeO2-ZrO2 composite oxides （CZ） were prepared through a co-precipitation method using magnesium hydrogen carbonate as the precipitating agent which was prepared from the cheap dolomite ores. The effects of peroxide oxidation time on the properties of CZs were studied. The crystal structures, surface areas, surface micromorphologies, redox performances and oxygen storage capacities of the as-synthesized CZs were studied by XRD, BET, SEM, TPR and oxygen pulse adsorption techniques, respectively. The results show that the addition of peroxide increases CZ＇s surface area, improves thermal stability, suppresses phase separation, and also increases the active surface oxygen amount. The surface area, aging property and oxygen storage capacity increase with prolonging the oxidation time and they reach to the maximum values at 30 rain, when the sample＇s 600 ℃ calcined fresh specific surface area, 1000 ℃ aged specific surface area as well as 500 ℃ oxygen storage capacity could reach 111.3 m2/g, 32.9 m2/g and 315μmol O2/g, respectively. However, their values change little when prolonging the oxidation time further.