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Organothermal Synthesis of Ultrafine Ceria Particles and Their Function

超细二氧化铈颗粒的有机热合成及其功能

基本信息

批准号：
13650890
负责人：
INOUE Masashi
金额：
$ 0.7万
依托单位：
Kyoto University
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (C)
财政年份：
2001
资助国家：
日本
起止时间：
2001 至 2002
项目状态：
已结题

项目摘要

The reaction of cerium metal tips having the superficial layer in 2-methoxyethanol at 200-300℃ followed by the removal of coarse ceria particles originating from the superficial layer yielded a dark brown clear solution, which was shown to be a colloidal solution containing ultrafine particles of ceria with a particle size of 2 nm ( reaction at 200-250℃.) This particle size is the smallest of the ceria particles synthesized thus fat The particle size increased with the increase in the reaction temperature or with prolonged reaction time. The ceria powder obtained by coagulation of the ceria colloidal particles showed crystal growth at as low as 500℃, which was concluded to be due to the large surface energy of ultrafine particles. Since the coagulation of the primary particles was so strong that micropores formed between the primary particles were too small to be accessed by nitrogen molecules. Therefore, surface area of the ceria powder was not so large as expected from the primary particles size. Strong coagulation was prohibited by the addition of polymer dispersant or by controlling the ionic strength of the coagulant, and ceria powder with large surface area and large pore size could be prepared. Aruthenium catalyst supported on the ceria powder having large pore size had quite a high performance for liquid phase oxidation of benzylalcohol, Colloidal solutions containing samarium and ytterbium oxides were also obtained by the similar reaction procedure. However, some rare earth metals were inert for the reaction. The reactivity of the rare earth metals was found to be connected with the crystal structure of the metals. For the rare earth metals with low reactivity, addition of acetic acid promoted the reaction and transpired colloidal solution of the corresponding metal oxide or hydroxide was obtained

具有表层的金属铈尖端在2-甲氧基乙醇中在200-300℃下反应，然后除去来自表层的粗二氧化铈颗粒，得到深棕色澄清溶液，该溶液显示为含有粒径为2nm的超细二氧化铈颗粒的胶体溶液（在200-250℃下反应）。该粒径是由此合成的二氧化铈颗粒中最小的，粒径随脂肪的增加而增大适当提高反应温度或延长反应时间。通过二氧化铈胶体颗粒凝聚获得的二氧化铈粉末在低至500℃的温度下就显示出晶体生长，这被认为是由于超细颗粒的大表面能所致。由于初级颗粒的凝聚力太强，初级颗粒之间形成的微孔太小，氮分子无法进入。因此，二氧化铈粉末的表面积并不像从初级颗粒尺寸预期的那样大。通过添加高分子分散剂或控制絮凝剂的离子强度来阻止强絮凝，可以制备出大表面积、大孔径的二氧化铈粉末。大孔径二氧化铈粉末负载的钌催化剂对苯甲醇的液相氧化具有相当高的性能，通过类似的反应过程也得到了含有钐和镱氧化物的胶体溶液。然而，一些稀土金属对反应呈惰性。发现稀土金属的反应性与金属的晶体结构有关。对于反应活性较低的稀土金属，加入乙酸促进反应，得到相应金属氧化物或氢氧化物的蒸发胶体溶液