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Preparation of Cu-Ce-Zr Composite Oxide Nano-particulates by SAS Process and the Controllable Synthesis of Hollow Structure

Author: SunHuanHua
Tutor: JiangHaoXi
School: Tianjin University
Course: Chemical processes
Keywords: supercritical anti-solvent (SAS) process CuO-CeO2-ZrO2 nano-particulates hollow structure
CLC: TB383.1
Type: Master's thesis
Year: 2010
Downloads: 55
Quote: 1
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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.

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