摘要
催化剂采用等量浸渍法，先后将Ｃｏ与贵金属组分浸于γ－Ａｌ２Ｏ３上，经５００℃焙烧，４５０℃氢气还原制得（ｍＣｏ３Ｏ４／ｍＡｌ２Ｏ３＝０．０８，ｍ贵金属／ｍ催化剂＝１／１０００）．ＣＯ氧化活性的测定结果表明，贵金属Ｐｔ和Ｐｄ与Ｃｏ之间具有明显的协同催化作用，而Ｒｈ与Ｃｏ的协同作用较差．在Ｃｏ－Ｐｔ／γ－Ａｌ２Ｏ３和Ｃｏ－Ｐｄ／γ－Ａｌ２Ｏ３上，ＣＯ１００％转化的温度较在Ｃｏ／γ－Ａｌ２Ｏ３上下降了约６０℃，而在Ｃｏ－Ｒｈ／γ－Ａｌ２Ｏ３上仅下降了２５℃左右．ＸＲＤ和ＸＰＳ的表征结果表明，Ｃｏ／γ－Ａｌ２Ｏ３中Ｃｏ以高分散的金属Ｃｏ相和类似ＣｏＡｌ２Ｏ４的尖晶石相存在，而Ｃｏ－Ｍ／γ－Ａｌ２Ｏ３（Ｍ＝Ｐｔ，Ｐｄ，Ｒｈ）催化剂中，Ｃｏ相已完全被还原为零价．高分散的金属钴相和贵金属相的协同作用，可能与氧从贵金属至Ｃｏ相上的溢流效应有关．
In this paper, the catalytic synergic effect between noble metals (Pt, Pd, Rh) and cobalt phases has been investigated for the reaction of CO oxidation. The bulk and surface structure of the catalysts have been characterized by using XRD and XPS techniques. The catalyst samples were prepared by equivalent wetness impregnation method. At first, γ Al 2O 3 was impregnated with the aqueous solution of Co(NO 3) 2·6H 2O. After drying and calcinating at 500℃ for 2 h, Co/ γ Al 2O 3 was impregnated with the solution of H 2PtCl 4, PdCl 2 or RhCl 3 respectively. All the precursors of catalyst samples were dried at 120℃, calcined at 500℃ for 2 h and reduced by hydrogen at 450℃ for 1 h( m Co 3O 4 / m Al 2O 3 =0 08, m noble metal / m catalyst =1/1000). The result of CO oxidation activity shows that there is obvious synergic effect between noble metals and cobalt phases. The results of structure characterization show that the cobalt exists as metal phase and Co 2+ Al 3+ spinel phase in Co/ γ Al 2O 3 catalyst, while it exists only as metal phase in Co M/ γ Al 2O 3 catalysts. Above results prove that Co metal is highly dispersed and it is one of the active phases during CO oxidation. The synergic effect is exhibited between noble metals and cobalt metal. As to the mechanism of synergic effect, it is speculated that there is oxygen spillover between noble metals and cobalt metal during CO oxidation.
出处
《催化学报》
CSCD
北大核心
1996年第3期189-192,共4页
基金
国家自然科学基金
关键词
钴
氧化铝
催化剂
铂
钯
铑
一氧化碳
协同效应
Cobalt/ γ
alumina catalyst
Platinum
Palladium
Rhodium
Carbon monoxide
Oxidation
Synergic effect
