化学
催化作用
密度泛函理论
沸石
星团(航天器)
离子键合
氢
阳离子聚合
氢键
解吸
氢原子
分子
物理化学
光化学
无机化学
结晶学
计算化学
高分子化学
吸附
有机化学
离子
烷基
计算机科学
程序设计语言
作者
Kyoichi Sawabe,Taisuke Hiro,Ken‐ichi Shimizu,Atsushi Satsuma
标识
DOI:10.1016/j.cattod.2010.03.078
摘要
Density functional theory (DFT) calculation was used to study the hydrogen promotion effect for the selective catalytic reduction (HC-SCR) of NO x over Ag-MFI zeolite. The nature of the bond between an Ag atom and MFI is ionic. One of the roles of hydrogen addition is to neutralize the cationic Ag atom by forming an AgH molecule. We propose that the formation of a Ag 4 cluster is achieved by the AgH diffusion as follows: 2AgH + Ag-Z-Ag→HAg 4 H-Z→Ag 4 -Z+ H 2 . With the presence of oxygen, the HAg 4 H cluster prefers the formation of HOO- adsorbate to the desorption of H 2 . O 2 is physisorbed on the Ag 4 cluster. Thus, the HAg 4 H cluster is important for the activation of oxygen. Another role of hydrogen addition is to reproduce the HAg 4 H cluster from the Ag 4 cluster which is generated by the SCR reaction from HOOAg 4 H species. Since time dependent DFT (TD-DFT) calculation shows that the UV absorption bands of the HAg 4 H cluster are weak, UV-vis measurements are not adequate for the study of the reaction mechanisms of HC-SCR.
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