State of Pd on H-ZSM-5 and other acidic supports during the selective reduction of NO by CH4 studied by EXAFS/XANES
State of Pd on H-ZSM-5 and other acidic supports during the selective reduction of NO by CH4 studied by EXAFS/XANES
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DOI：
10.1016/s0926-3373(97)00008-8
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发表时间：
1997-12-05
影响因子：
22.1
通讯作者：
Resasco, DE
中科院分区：
文献类型：
--
作者：
Ali, A;Alvarez, W;Resasco, DE
在一系列钯催化剂上研究了甲烷选择性还原NO的反应。当负载在非酸性材料上时，钯对NO的转化完全没有选择性，而对甲烷的燃烧非常活跃。相比之下，负载在酸性（质子）材料（H-ZSM-5、H-丝光沸石、硫酸化氧化锆）上的低负载Pd催化剂表现出高得多的选择性。X射线吸收研究（XANES和EXAFS）进行了几个Pd催化剂之前和之后，在氧气的存在下还原NO。这些研究表明，在暴露于反应混合物（CH 4 + NO + O-2）时，Pd被氧化。氧化的Pd物种的形态强烈地依赖于金属负载量和载体的酸性。在酸性载体上的低Pd负载催化剂上，最初存在的金属Pd颗粒通过反应混合物迅速转化为Pd 2+离子。相比之下，在非酸性材料上，Pd颗粒转化为PdO团簇。这些团簇对甲烷燃烧具有高催化活性，导致低SCR选择性。(C)1997年Elsevier Science B.V.
The selective reduction of NO by methane has been studied on a series of Pd catalysts. When supported on non-acidic materials, palladium is totally unselective for the conversion of NO and very active for the combustion of methane. By contrast, lowloading Pd catalysts supported on acidic (protonic) materials (H-ZSM-5, H-Mordenite, sulfated zirconia) exhibit much higher selectivity. X-ray absorption studies (XANES and EXAFS) were conducted on several Pd catalysts before and after the reduction of NO in the presence of oxygen. These studies have demonstrated that, upon exposure to the reaction mixture (CH4 + NO + O-2), Pd gets oxidized. The morphology of the oxidized Pd species strongly depends on the metal loading and the acidity of the support. On low Pd loading catalysts over acidic supports, the metallic Pd particles, initially present, are rapidly transformed in Pd2+ ions by the reaction mixture. By contrast, on the non-acidic materials, the Pd particles are transformed into PdO clusters. These clusters have high catalytic activity for the methane combustion, resulting in low SCR selectivities. (C) 1997 Elsevier Science B.V.