Ag cluster as active species for SCR of NO by propane in the presence of hydrogen over Ag-MFI

被引:132
作者
Shibata, J
Takada, Y
Shichi, A
Satokawa, S
Satsuma, A [1 ]
Hattori, T
机构
[1] Nagoya Univ, Grad Sch Engn, Dept Appl Chem, Chikusa Ku, Nagoya, Aichi 4648603, Japan
[2] Tokyo Gas Co Ltd, Tech Res Inst, Minato Ku, Tokyo 1050023, Japan
关键词
HC-SCR; Ag-MFI; H-2; active species; UV-vis; Ag cluster;
D O I
10.1016/j.jcat.2003.11.007
中图分类号
O64 [物理化学(理论化学)、化学物理学];
学科分类号
070304 ; 081704 ;
摘要
The effect of the addition of H-2 on SCR of NO by C3H8 over Ag-MFI was studied. SCR activity over Ag-MFI was significantly enhanced by the addition of H-2 below 673 K. Upon the removal of H-2 from reaction gases, NO reduction activity decreased to the same conversion before the addition of H-2, indicating that the promotion effect of H-2 on NO reduction activity was reversible. UV-vis spectroscopy was used to identify the active structure of Ag species during the C3H8-SCR. Ag+ ion was mainly in existence during the C3H8-SCR in the absence of H-2, while Ag-n(delta+) clusters (2 less than or equal to n less than or equal to 4), together with Ag+ ion, were formed in the presence of H-2. NO reduction rate and band intensity due to the Ag-n(delta+) cluster increased with an increase in H-2 concentration. On the other hand, formation of a metallic Ag-m cluster (3 less than or equal to m less than or equal to 5) and Ag metal increased the contribution of nonselective hydrocarbon combustion to the overall reaction. From the above results, it is indicated that a moderately agglomerated Ag-n(delta+) cluster is a highly active species for the SCR by C3H8 in the presence of H-2, and that the role of H-2 is reduction of Ag+ ion to Ag-n(delta+) clusters. Ag species is markedly influenced by concentrations of gaseous components not only H-2 but also NO and C3H8. In addition, the type of Ag species was reversibly changed among Ag+ ion, Ag-n(delta+) clusters, and metallic Ag-m clusters together with Ag metal, depending on the reaction atmosphere, which suggests that gaseous components control the balance among Ag species on the catalyst. (C) 2003 Elsevier Inc. All rights reserved.
引用
收藏
页码:368 / 376
页数:9
相关论文
共 41 条
[1]   Characterization of highly active silver catalyst for NOx reduction in lean-burning engine exhaust [J].
Aoyama, N ;
Yoshida, K ;
Abe, A ;
Miyadera, T .
CATALYSIS LETTERS, 1997, 43 (3-4) :249-253
[2]   REVERSIBLE REDOX BEHAVIOR BETWEEN SILVER CATIONS AND SILVER METAL PARTICLES IN HYDRATED AG-Y ZEOLITES [J].
BABA, T ;
AKINAKA, N ;
NOMURA, M ;
ONO, Y .
JOURNAL OF THE CHEMICAL SOCIETY-FARADAY TRANSACTIONS, 1993, 89 (03) :595-599
[3]  
Baerlocher Ch., 2001, ATLAS ZEOLITE FRAMEW, P184
[4]   FAR-INFRARED STUDIES OF SILVER ATOMS, SILVER IONS, AND SILVER CLUSTERS IN ZEOLITE-A AND ZEOLITE-Y [J].
BAKER, MD ;
OZIN, GA ;
GODBER, J .
JOURNAL OF PHYSICAL CHEMISTRY, 1985, 89 (02) :305-311
[5]   Supported Ag catalysts for the lean reduction of NO with C3H6 [J].
Bethke, KA ;
Kung, HH .
JOURNAL OF CATALYSIS, 1997, 172 (01) :93-102
[6]   REDOX BEHAVIOR OF TRANSITION-METAL IONS IN ZEOLITES .2. KINETIC STUDY OF REDUCTION AND REOXIDATION OF SILVER-Y ZEOLITES [J].
BEYER, H ;
JACOBS, PA ;
UYTTERHOEVEN, JB .
JOURNAL OF THE CHEMICAL SOCIETY-FARADAY TRANSACTIONS I, 1976, 72 :674-685
[7]  
Beyer H. K., 1982, Stud.Surf. Sci. Catal, V12, P95, DOI [10.1016/S0167-2991(09)60997-6, DOI 10.1016/S0167-2991(09)60997-6]
[8]   On the nature of the silver phases of Ag/Al2O3 catalysts for reactions involving nitric oxide [J].
Bogdanchikova, N ;
Meunier, FC ;
Avalos-Borja, M ;
Breen, JP ;
Pestryakov, A .
APPLIED CATALYSIS B-ENVIRONMENTAL, 2002, 36 (04) :287-297
[9]  
BOGDANCHIKOVA NE, 1994, STUD SURF SCI CATAL, V84, P1067
[10]   GROWTH OF SILVER PARTICLES IN AQUEOUS-SOLUTION - LONG-LIVED MAGIC CLUSTERS AND IONIC-STRENGTH EFFECTS [J].
ERSHOV, BG ;
JANATA, E ;
HENGLEIN, A .
JOURNAL OF PHYSICAL CHEMISTRY, 1993, 97 (02) :339-343