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Synthesis of New Oxide Solid Solutions of High Redox Activities and Their Application to Automotive Exhaust Catalysts

高氧化还原活性新型氧化物固溶体的合成及其在汽车尾气催化剂中的应用

基本信息

批准号：
17350100
负责人：
IMANAKA Nobuhito
金额：
$ 7.94万
依托单位：
Osaka University
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (B)
财政年份：
2005
资助国家：
日本
起止时间：
2005 至 2006
项目状态：
已结题

项目摘要

Because of recent environmental regulations, reduction of the redox temperature and addition of high thermal stability are urgent subjects for oxide solid solutions employed in the automotive exhaust catalysts.In this study, low temperature reduction behavior of CeO_2-ZrO_2-Bi_2O_3 solid solutions was promoted by the addition of silver, which is an oxygen permeable component. The mechanism of the behavior was attributed to the synergetic effects of the partial solution of silver into the CeO_2-ZrO_2-Bi_2O_3 lattice and the surface deposition of silver on the solid solution. The reactivity of oxygen in the bulk of the catalyst greatly improves the soot combustion activities at low temperatures.Furthermore, we prepared and characterized a CeO_2-ZrO_2-Bi_2O_3 solid solution supported on La-stabilised γ-Al_2O_3 (CZB/Al_2O_3), which has the potential to be a key material in advanced catalytic converters. The low temperature redox activities demonstrated by the CZB/Al_2O_3 catalyst, which is effective at low temperatures below 100 ℃ even after calcination at 1000 ℃, have never been attained in conventional catalysts without help of precious metals. By the deposition of the CeO_2-ZrO_2-Bi_2O_3 solid solution on the surface of γ-Al_2O_3, particle size of the solid solution considerably decreased to a nanoscale, and the dynamic oxygen storage capacity became 7.5 times of the bulk CeO_2-ZrO_2-Bi_2O_3 catalyst without the γ-Al_2O_3 support (at 600 ℃). Studies using CH_4 oxidation, as a model reaction, showed that the redox activities of such catalysts at low temperatures correlates with their catalytic activities.

由于环保法规的要求，降低氧化物固溶体的氧化还原温度和提高其热稳定性成为汽车尾气催化剂的迫切课题，本研究通过添加具有透氧性的银促进CeO_2-ZrO_2-Bi_2O_3固溶体的低温还原行为。其机理是由于银部分固溶于CeO_2-ZrO_2-Bi_2O_3晶格和银在固溶体表面沉积的协同作用。此外，我们还制备并表征了一种以La稳定的γ-Al_2O_3为载体的CeO_2-ZrO_2-Bi_2O_3固溶体（CZB/Al_2O_3），该固溶体有望成为先进催化转化器的关键材料。CZB/Al_2O_3催化剂在1000 ℃焙烧后仍能在低于100 ℃的低温下氧化还原，其低温氧化还原活性是传统催化剂在没有贵金属辅助的情况下所不能达到的。CeO_2-ZrO_2-Bi_2O_3固溶体在γ-Al_2O_3表面的沉积，使固溶体的粒径明显减小到纳米级，其动态储氧能力是未负载γ-Al_2O_3的CeO_2-ZrO_2-Bi_2O_3催化剂的7.5倍（600 ℃）。以甲烷氧化为模型反应的研究表明，低温下的氧化还原活性与催化剂的活性相关。