【作者】 孙焕花；

【导师】 姜浩锡；

【作者基本信息】 天津大学 ， 化学工艺， 2010， 硕士

【摘要】 铈锆氧化物固溶体因具有储放氧性能常被用作催化剂或者催化剂载体。但其催化活性温度比较高,储氧量（Oxygen Storage Capacity, OSC）也有待于进一步改善。基于改进上述缺点,众多学者对掺杂第三组分改性的铈锆氧化物固溶体做了研究,发现不同的制备方法对复合氧化物的结构及物化性能有很大影响。超临界抗溶剂法（Supercritical Anti-Solvent, SAS）是一种新兴的微粒制备技术,在聚合物、制药、催化剂等领域有很好的应用前景。本课题组采用超临界抗溶剂法成功制备出铈锆氧化物纳米颗粒,与传统方法相比,具有粒径小且分布均匀、形状规则、热稳定性好、比表面积大等优点。在前期研究基础上,本文采用SAS法制备在铈锆氧化物固溶体中添加第三组分铜的复合氧化物纳米颗粒,并对其晶体结构、氧化还原性能、储氧量性能等进行了表征,同时对铜铈锆复合氧化物中空结构颗粒的形成条件做了进一步讨论。本文通过SAS法成功制备出铜铈锆复合氧化物纳米颗粒的前驱体,经焙烧后得到粒径为30⁵0nm的铜铈锆复合氧化物纳米颗粒。表征结果发现,Cu²⁺离子已进入到CeO₂晶格中形成了CuO-CeO₂固溶体,其储氧量由506μmol·g^-1增加到636.9μmol·g^-1,同时三元复合氧化物的还原峰温度由600℃左右降低到120²40℃。采用SAS法制备铜铈锆复合氧化物时,随着溶液浓度增加,复合氧化物颗粒由中空纳米球变为实心纳米球。相平衡研究发现,溶质和温度对混合物临界（Mixture Critical Point,MCP）线的影响比较显著,乙酰丙酮铈、乙酰丙酮锆及乙酸铜的添加均能使CO₂-甲醇体系的MCP线向高压发生偏移,且乙酸铜的添加对CO₂-甲醇体系的MCP线影响程度最大;CO₂-甲醇体系的MCP线随制备温度的降低而向低压方向偏移。最后,对铜铈锆复合氧化物中空纳米球的适宜条件可控合成进行了探索研究。更多还原

【Abstract】 Ceria-zirconia solid solution is of excellent oxygen storage and release properties, thus it is often apllied as catalysts and carriers. However, the activated temperature of Ceria-zirconia is rather high, and the OSC （Oxygen Storage Capacity） should be also improved. Therefore, a lot of researchers have studied the ceria-zirconia solid solution doped with the third component, and found the preparation process has a considerable effect on the structure and physico-chemical properties of the composite oxide catalyst. Supercritical Anti-Solvent （SAS） process is a novel technique for particulates formation, which has promicing application potential in the fields of polymer, pharmacy, catalyst and more.In the previous works, the hollow nano-particulates of ceria-zirconia solid solution oxide were prepared by the SAS process successfully. Compared with the conventional methods, the composite oxides nano-particulates produced had the advantages of uniform particle size, regular shape, good thermal stability and large specific surface area. In this work, the copper component is addeded into the ceria-zirconia solid solution by the SAS process, and the crystal structure, redox property and oxygen storage capacity were characterized. Meanwhile, the proper conditions in favor of formation of particulates with hollow structure were discussed.The amorphous precursor of CuO-CeO₂-ZrO₂ nano-particulates was prepared by the SAS process successfully, and after calcinations, the nano-particulates with the average particle diameter of about 30⁵0 nm were obtained. It was found by the characterizations, the Cu²⁺cations were penetrated into the lattice of CeO₂ to form solid solution, the reduction temperature was decreased from 600℃to 120²40℃and the OSC value was improved from 506.0μmol·g^-1 to 636.9μmol·g^-1. The hollow structure was disappeared as with the increase of solution concentration, and the nano-particulates with solid structure were formed again. The phase equilibrium study revealed that solute and temperature were two more apparent influencing factors on the MCP （Mixture Critical Point） lines. It was demonstrated that the presence of solutes such as Ce（acac）3, Zr（acac）4 and Cu（CH3COO）2 could move the MCP line for the ternary system towards higher pressure, compared with those of the corresponding methanol-carbon dioxide binary system. The adding of cupric acetate showed the most obvious effect on the MCP line for the system. Moreover, as with the preparation temperature decreased, the MCP line for the ternary system would move towards lower pressure. Finally, the optimal conditions for synthesis of nano-particulates copper-ceria-zirconia ternary composite oxide with controllable hollow structure were investigated.更多还原