Reductive Activation of O2 with H2-Reduced Silver Clusters as a Key Step in the H2-Promoted Selective Catalytic Reduction of NO with C3H8 over Ag/Al2O3
Reductive Activation of O2 with H2-Reduced Silver Clusters as a Key Step in the H2-Promoted Selective Catalytic Reduction of NO with C3H8 over Ag/Al2O3
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DOI：
10.1021/jp066147f
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发表时间：
2007
影响因子：
3.7
通讯作者：
K. Shimizu;Masaoshi Tsuzuki;Kazuo Kato;S. Yokota;and Kazu Okumura;A. Satsuma
中科院分区：
文献类型：
--
作者：
K. Shimizu;Masaoshi Tsuzuki;Kazuo Kato;S. Yokota;and Kazu Okumura;A. Satsuma
通过催化和光谱研究，探讨了添加H_2对丙烷选择性催化还原NO(C_3H_8-SCr)活性显著提高的机理。原位UV−Vis、原位EXAFS、IR和微量热法实验表明，573K时，Ag+在Ag/Al_2O_3上还原生成Al_2O_3上的质子和部分还原的AgN-δ+团簇，并聚集成更大的Ag团簇。在H2+O2和H2辅助的C3H8-SCR反应中，Ag+离子和AgNδ+共存。O2的再氧化导致团簇重新分散为Ag+离子，并伴随着质子反应。用不同负载量的Ag/Al_2O_3考察了团簇大小、氧化还原性能和催化活性之间的关系。在H_2辅助的C_3H_8-SCR反应中，稳态NO还原速率与AgN-δ+的量有很好的相关性。结果表明，AgN-δ+是活性物种，而单体Ag+和金属Ag是活性物种。
The mechanistic cause of the dramatic activity improvement of alumina-supported silver (Ag/Al2O3) by H2 addition for the selective catalytic reduction of NO with propane (C3H8-SCR) was investigated by catalytic and spectroscopic studies. In situ UV−vis, in situ EXAFS, IR, and microcalorimetric experiments show that H2 reduction of Ag+ ions on Ag/Al2O3 at 573 K yields protons on alumina and partially reduced Agnδ+ clusters, which are subsequently aggregated to larger Ag clusters. During H2 + O2 and H2-assisted C3H8-SCR reactions, Ag+ ions and Agnδ+ coexist. Reoxidation with O2 results in the redispersion of the cluster to Ag+ ion, accompanying a reaction of protons. The relationship between cluster size, redox properties, and catalytic activity is examined using Ag/Al2O3 of different Ag loadings. The steady-state NO reduction rate correlates fairly well with the amount of Agnδ+ during the H2-assisted C3H8-SCR reaction. It is shown that Agnδ+ is the active species, whereas monomeric Ag+ ion and metallic Ag ...