Preparation of supported Pt-M catalysts (M = Mo and W) from anion-exchanged hydrotalcites and their catalytic activity for low temperature NO-H2-O2 reaction
Preparation of supported Pt-M catalysts (M = Mo and W) from anion-exchanged hydrotalcites and their catalytic activity for low temperature NO-H2-O2 reaction
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DOI：
10.1016/j.apcatb.2007.02.012
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发表时间：
2007-07-31
影响因子：
22.1
通讯作者：
Machida, M.
中科院分区：
文献类型：
--
作者：
Hamada, S.;Hibarino, S.;Machida, M.
在负载型双金属催化剂 Pt-Mo 和 Pt-W 上研究了 NO-H-2-O-2 反应，该催化剂是通过将水滑石类 Mg-Al 双层氢氧化物与 Pt(NO2)(4)(2-)、MoO42- 和/或 WO42- 共交换，然后在 H-2 中于 600 ℃ 加热而制备的。当还原处理后的催化剂在不存在O-2的情况下暴露于NO和H 2 的混合物时，可以明显地看到Pt-Mo相互作用。 Pt-HT 催化剂在 70 ℃ 时显示出几乎完全的 NO 转化，而 Pt-Mo-HT 则显示出可忽略不计的转化。然而，当暴露于O 2 时，Pt-Mo-HT在≥30℃的最低温度下表现出NO转化，相比之下Pt-HT所需的≥60℃。 EXAFS/XANES、XPS 和 IR 结果表明，Mo 的作用对氧化态非常敏感，即，假设 Pt 颗粒中存在的氧化 Mo 物种会延迟 NO 氧化吸附为 NO3，并促进低温下 NO 催化转化为 N2O。 (C) 2007 Elsevier B.V. 保留所有权利。
The NO-H-2-O-2 reaction was studied over supported bimetallic catalysts, Pt-Mo and Pt-W, which were prepared by coexchange of hydrotalcite like Mg-Al double layered hydroxides by Pt(NO2)(4)(2-), MoO42-, and/or WO42- and subsequent heating at 600 degrees C in H-2. The Pt-Mo interaction could obviously be seen when the catalyst after reduction treatment was exposed to a mixture of NO and H2 in the absence Of O-2. The Pt-HT catalyst showed the almost complete NO conversion at 70 'C, whereas the Pt-Mo-HT showed a negligible conversion. Upon exposure to 02, however, Pt-Mo-HT exhibited the NO conversion at the lowest temperature of >= 30 degrees C, compared to >= 60 degrees C required for Pt-HT. EXAFS/XANES, XPS and IR results suggested that the role of Mo is very sensitive to the oxidation state, i.e., oxidized Mo species residing in Pt particles are postulated to retard the oxidative adsorption of NO as NO3 and promote the catalytic conversion of NO to N2O at low temperatures. (C) 2007 Elsevier B.V. All rights reserved.