摘要
采用等量分步浸渍法先后将Ｃｏ与贵金属组份浸于ＣｅＯ２上，经５００℃焙烧２ｈ，４５０℃氢气还原１ｈ制得Ｃｏ－Ｐｔ／ＣｅＯ２和Ｃｏ－Ｒｈ／ＣｅＯ２催化剂。活性测试结果表明，贵金属与Ｃｏ之间具有催化协同效应。对ＣＯ氧化，Ｐｔ与Ｃｏ的协同效应较显著，而对富氧条件下ＣＨ４选择还原ＮＯ，Ｒｈ与Ｃｏ的协同效应更为明显。ＸＰＳ和ＥＸＡＦＳ结果一致表明，经Ｈ２还原后，样品Ｃｏ／ＣｅＯ２、Ｃｏ－Ｐｔ／ＣｅＯ２和Ｃｏ－Ｒｈ／ＣｅＯ２中Ｃｏ均以高分散的金属钴形式存在，ＸＲＤ已难以检测。此外，样品表面Ｃｏ原子百分数的提高及Ｃｏ－Ｃｏ壳层配位数的下降均表明，微量Ｐｔ或Ｒｈ的加入进一步提高了金属Ｃｏ的分散性。对微量Ｐｔ和Ｒｈ在Ｃｏ／ＣｅＯ２中的作用作了一些探讨。
Co-Pt/CeO_2 and Co-Rh/CeO_2 (Co_3O_4/CeO_2=8%,M/CeO_2=0.1%,M=Pt or Rh) catalysts were prepared by successive wetness impregnation method .The results of activity measurements show that there exists catalytic synergy effect between noble metals and cobalt. For CO oxidation, the synergy effect between Pt and Co is more obvious than that between Rh and Co. But for the selective catalytic reduction of NO by CH4 in the presence of exces soxygen, the synergy effect between Rh and Co is more obvious. Both the results of XPS and EXAFS indicate that all cobalt in Co/CeO2, Co-Pt/CeO2 and Co-Rh/CeO2 exists in metallic state which is so highly dispersed that it is difficult to detect by XRD. The increase of cobalt percentage on the catalyst surface and the decrease of Co-Co shell coordination number show that the addition of the small amount of platinum or rhodium to Co/CeO2 has improved the dispersion of cobalt phase on the surface of Co/CeO2. The effects of the small amount of Pt or Rh on Co/CeO2 are discussed.
基金
国家自然科学基金
关键词
催化剂
钴
铈
铂
铑
汽车尾气净化
Pt(Rh)-Co/CeO2 catalysts Catalytic synergy effect Structure CO oxidation NO selctive reductionn
