Structure of active Ag clusters in Ag zeolites for SCR of NO by propane in the presence of hydrogen

Shibata, Junji; Shimizu, Ken‐ichi; Takada, Yasunobu; Shichi, Akira; Yoshida, Hisao; Satokawa, Shigeo; Satsuma, Atsushi; Hattori, Tadashi

doi:10.1016/j.jcat.2004.08.007

Cited by 176 publications

(208 citation statements)

References 33 publications

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“…8), in line with earlier reports [41][42][43][44][45][46][47][48]. The band at 245 nm for as prepared Ag 6.0 SiBEA is more pronounced than that for as prepared Ag 3.0 SiBEA.…”

Section: Nature Of the Silver Insupporting

confidence: 91%

“…However, there is still lack of data in the literature concerning application of silver-containing zeolites in the SCR of NO x . According to previous reports, dispersed silver species seem to be active catalytic centers of SCR of NO on Ag-MFI zeolites [18,19]. However, silver is not well dispersed in such materials, which contain silver in the form of various species, i.e., ions, nanoclusters, and metallic nanoparticles.…”

Section: Introductionmentioning

confidence: 95%

See 1 more Smart Citation

Identification of the silver state in the framework of Ag-containing zeolite by XRD, FTIR, photoluminescence,¹⁰⁹Ag NMR, EPR, DR UV-vis, TEM and XPS investigations

Popovych

Kyriienko

Soloviev

et al. 2016

Phys. Chem. Chem. Phys.

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“…8), in line with earlier reports [41][42][43][44][45][46][47][48]. The band at 245 nm for as prepared Ag 6.0 SiBEA is more pronounced than that for as prepared Ag 3.0 SiBEA.…”

Section: Nature Of the Silver Insupporting

confidence: 91%

Section: Introductionmentioning

confidence: 95%

Identification of the silver state in the framework of Ag-containing zeolite by XRD, FTIR, photoluminescence,¹⁰⁹Ag NMR, EPR, DR UV-vis, TEM and XPS investigations

Popovych

Kyriienko

Soloviev

et al. 2016

Phys. Chem. Chem. Phys.

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“…The addition of small amounts of hydrogen significantly improves the performance of silver alumina catalysts by increasing the conversion of NO and by decreasing the required reaction temperature. 2,10,30,31 This hydrogen effect is presented in Figure 4 for the conversion of NO (A) and propene (B) for 5AgB. Similar activity results were obtained for 7AgB (not shown).…”

Section: Resultssupporting

confidence: 74%

“…1,[4][5][6][7][8][9][10][11][12] The large Ag 0 clusters cause unselective combustion of the reducing agent and the formation of N 2 O, a harmful greenhouse gas, whereas all of the other silver species have been proposed to be the active sites for SCR. 1,9,[11][12][13][14] The lack of certainty on the type of the active site is due to the complex nature of the SCR reaction, 1,15 the mobility of silver species under reaction condition, 3,16 and the influence of temperature and gas-phase composition on the formed surface species.…”

Section: Introductionmentioning

confidence: 99%

New Insights into the Active Surface Species of Silver Alumina Catalysts in the Selective Catalytic Reduction of NO

et al. 2010

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The performance of silver alumina catalysts and silver aluminate was studied in the selective catalytic reduction (SCR) of NO by propene. The use of boehmite during the impregnation step ensured a strong interaction between the silver species and the alumina surface in the final calcined catalyst. Thus, higher silver loadings (5-7 wt % silver) could be used without significant loss in selectivity to N 2 during SCR. The nature of the silver species and the formation of adsorbed surface species during SCR and hydrogen-assisted SCR (H 2 -SCR) was studied by activity measurements and by combined in situ IR and X-absorption spectroscopic measurements. The combination of these techniques in the same reaction cell allowed simultaneous monitoring of the state of silver and the formation of surface species under realistic reaction conditions. The active silver species on alumina support were concluded to be 2-dimensional oxidic Ag n δ+ species. Silver aluminate was ruled out as a possibility for an active phase for the SCR reaction. The oxidic Ag n δ+ species were present under both SCR and H 2 -SCR reaction conditions and even on a prereduced catalyst under the SCR reaction conditions. Hydrogen is proposed to enhance the formation of adsorbed surface species, especially nitrites, but not to change the nature of the active silver sites.

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“…To better understand issues as varied as the mechanism of selective reduction of NOx or the hydrocarbon adsorption process of silver based catalysts, it is necessary to determine the chemical state and the location of silver nanoparticles in the zeolitic framework. 3,13,18,19 Recently, a considerable number of studies have explored the catalytic properties of silver-zeolite catalysts for the SCR of NOx by hydrocarbons [20][21][22] or alcohols. [23][24][25] Our research group reported that silver-exchanged Na-mordenite catalysts were active and selective in the removal of nitrogen oxides using butane or toluene as reducing agents.…”

Section: Introductionmentioning

confidence: 99%

Study of the Nature and Location of Silver in Ag-Exchanged Mordenite Catalysts. Characterization by Spectroscopic Techniques

et al. 2013

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Catalysts based on Na-mordenite (symbolized as 'M') exchanged with 5, 10 and 15 wt. % of Ag were characterized by XPS, EXAFS, XANES and UV-Vis DRS spectroscopic techniques in order to investigate the effect of different treatments on the chemical state and surface concentration of silver species. The Ag x M catalysts were analyzed in oxidizing (O 2 ) or reducing (H 2 /Ar) atmospheres and also after being used in the selective catalytic reduction of NOx or in successive cycles of toluene adsorption/desorption.In calcined samples, EXAFS profiles showed two types of Ag-O spheres of coordination, one due to a dispersed phase of silver oxide and the other, to Ag + ions in interaction with the oxygen of the zeolite framework. The UV-Vis DRS spectra showed the coexistence of isolated Ag + , Ag n δ+ (n < 10) cationic clusters and Ag x O particles. In addition, through the modified Auger parameter (α'), calculated from XPS measurements, it was possible to identify Ag + ions at exchange sites (α'~722 eV) and Ag x O (α'~725 eV) highly dispersed on the surface. Both species constitute stable active centers for the SCR of NOx under severe reaction conditions. However, during the adsorption-desorption of toluene, the reduction of silver oxides produces Ag(0) due to thermal hydrocarbon decomposition.

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Structure of active Ag clusters in Ag zeolites for SCR of NO by propane in the presence of hydrogen

Cited by 176 publications

References 33 publications

Identification of the silver state in the framework of Ag-containing zeolite by XRD, FTIR, photoluminescence,¹⁰⁹Ag NMR, EPR, DR UV-vis, TEM and XPS investigations

Identification of the silver state in the framework of Ag-containing zeolite by XRD, FTIR, photoluminescence,¹⁰⁹Ag NMR, EPR, DR UV-vis, TEM and XPS investigations

New Insights into the Active Surface Species of Silver Alumina Catalysts in the Selective Catalytic Reduction of NO

Study of the Nature and Location of Silver in Ag-Exchanged Mordenite Catalysts. Characterization by Spectroscopic Techniques

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Structure of active Ag clusters in Ag zeolites for SCR of NO by propane in the presence of hydrogen

Cited by 176 publications

References 33 publications

Identification of the silver state in the framework of Ag-containing zeolite by XRD, FTIR, photoluminescence,109Ag NMR, EPR, DR UV-vis, TEM and XPS investigations

Identification of the silver state in the framework of Ag-containing zeolite by XRD, FTIR, photoluminescence,109Ag NMR, EPR, DR UV-vis, TEM and XPS investigations

New Insights into the Active Surface Species of Silver Alumina Catalysts in the Selective Catalytic Reduction of NO

Study of the Nature and Location of Silver in Ag-Exchanged Mordenite Catalysts. Characterization by Spectroscopic Techniques

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Product

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Identification of the silver state in the framework of Ag-containing zeolite by XRD, FTIR, photoluminescence,¹⁰⁹Ag NMR, EPR, DR UV-vis, TEM and XPS investigations

Identification of the silver state in the framework of Ag-containing zeolite by XRD, FTIR, photoluminescence,¹⁰⁹Ag NMR, EPR, DR UV-vis, TEM and XPS investigations