稳定化ZrO_2超微粉体的制备及其催化CO氧化反应性能

Preparation of Cubic ZrO_2 Ultrafine Powders and Characterization of Their Catalytic Properties for CO Total Oxidation

采用凝胶 超临界流体干燥工艺制备无团聚ZrO2(CaO)超微粉体,考察ZrO2(CaO)及M/ZrO2(CaO)催化剂对CO完全氧化反应的催化活性.研究发现,超临界流体干燥可以有效地防止凝胶干燥过程中硬团聚体的生成,从而获得高比表面积、大孔体积、小粒径且具有良好单分散性能的ZrO2(CaO)粉体.作为催化剂活性组分及载体,超微ZrO2(CaO)在CO完全氧化反应中表现出优良的性能.未担载任何活性组分的超微ZrO2(CaO)是CO完全氧化反应的高温催化剂,其50%转化温度约为280℃,100%转化温度为550℃;以超微ZrO2(CaO)粉体作载体,担载Ni,Cu和Pd的负载型催化剂对CO低温氧化表现出较高的催化活性.

The fluoritetype zirconia powders were synthesized by various methods and were evaluated for the total oxidation of carbon monoxide. The preparation involved coprecipitation followed by two different drying approaches, i.e. common drying and alcohol launderingsupercritical fluid drying technology. The properties of ZrO2 (CaO) catalysts were sensitive to the drying methods. And the supercritical fluid drying technology could effectively alleviate the hard agglomeration of grains during the drying process, with the result that the morphology of the ultrafine powder retained the network texture of the original gel. The ultrafine powder was characterized by its small particle size, better monodispersibility, high specific surface area, and large pore volume. As catalyst and supporters for the total oxidation of carbon monoxide, the ultrafine fluoritetype zirconia showed high catalytic activity. Cubic fluoritetype zirconia ultrafine powder, without any active component on it, showed relatively high activity with lightoff temperature about 280 ℃(50% conversion) and 550 ℃(100% conversion). Moreover, Ni, Cu and Pd supported by such special supporters exhibited extremely high activity at low temperatures.