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Nakahira, A.; Nishimura, Shuichi; Aritani, Hirofumi; Yamamoto, Takashi; Ueda, Shigenori

doi:10.1023/a:1017521219062

Cited by 9 publications

(6 citation statements)

References 7 publications

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“…The results of characterization mainly by using XRD and SEM were described in previous papers. 28,35 In summary, the Fe-MOR materials synthesized hydrothermally have a mordenite structure with high crystallinity; however, the crystallinity of Fe100MOR was lower than those of other Fe-MOR samples.…”

Section: Resultsmentioning

confidence: 96%

“…The Fe-MOR samples are prepared by the method described in a separate paper. 28 In brief, Fe-mordenites with several Fe/ (Fe + Al) ratios were synthesized hydrothermally at 423 K for more than 7 days. The Na2O-Fe2O3(and/or Al2O3)-SiO2-H2O system and TEA were used as the template.…”

Section: Methodsmentioning

confidence: 99%

“…As a result, Fe-substituted Al-mordenite materials can be expected to act as appropriate catalysts for selective oxidation and SCR of NO with high and durable activity. In our previous study, 28 Fe-MOR with high crystallinity could be synthesized hydrothermally by using the tetraethylammonium (TEA) template, and the Fe ratio (Fe/(Fe + Al)) in the Fe-mordenites could be controlled in the range of 0-100 mol % Fe. In this study, however, the results of characterization were supplied only by means of XRD and SEM.…”

Section: Introductionmentioning

confidence: 99%

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Local Structure of Framework Iron in Fe-Substituted Al-Mordenites by Fe K Edge XAFS

et al. 2002

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The Fe-substituted Al-mordenites (Fe-MOR) with several Fe ratios were synthesized, and the detailed structure was obtained by means of Al K edge XANES and Fe K edge XAFS. From the results of the N2-adsorption isotherm, the Fe-substituted mordenites with an Fe/(Fe + Al) ratio as high as 75 mol % have a high crystallinity and appropriate micropore. The completely substituted mordenite (Fe100MOR) shows low pore volume and mordenite crystallinity. The Al K edge XANES results show the smaller effect of structural change around Al ions by Fe (25 mol %) substitution. Fe K edge XAFS results indicate existence of tetrahedral Fe ions into the mordenite framework in all the Fe ratios. The local structure around the Fe3+ ions is quite different from that around the Fe-modified mordenites. The Fe−O distance increases with an increase in Fe content. This suggests the distortion of the zeolite framework in the local structure of the mordenites. It is concluded that the stable structure around the Fe3+ ions in the Fe-substituted mordenites is brought up to about 75 mol % in the Fe ratio.

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Section: Resultsmentioning

confidence: 96%

Section: Methodsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Local Structure of Framework Iron in Fe-Substituted Al-Mordenites by Fe K Edge XAFS

et al. 2002

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“…3 In brief, GaMFI with several Si/(Ga + Al) 2 ratios were prepared from aluminum chloride, iron(II) sulfate, pentahydrated gallium nitrate, sodium silicate, and TPABr (as a template for MFI) mixed solution. They were stirred for ca.…”

Section: Experimental Synthesis Of Metallosilicatesmentioning

confidence: 99%

“…On the other hand, metallosilicates are an appropriate material because active transition-metal ions are incorporated onto the framework. 3 For example, Fe 3+ -substituted MOR zeolites show high NO-SCR activity for methane. 4 But deactivation during the reaction is a major issue.…”

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confidence: 99%

Gallosilicate-Based Catalysts for NOx-SCR with CH4

Nagashima¹,

Nakamura²,

Okada³

et al. 2009

Bulletin of the Chemical Society of Japan

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Ga-incorporated H-MFI (GaMFI) metallosilicate catalysts show robust activity for selective catalytic reduction of NO x (NO x -SCR) with CH 4 , although the reactivity of NO CH 4 is very low in the absence of O 2 . Over these catalysts, NO x CH 4 reaction proceeds selectively in the presence of O 2 . In contrast, FeMFI shows high activity for NO CH 4 reaction without O 2 , although no reactivity is shown in the presence of O 2 . In addition, transition-metal ion modification on FeMFI does not enhance NO x -SCR activity. From the results of XRD and XAFS characterization at Ga and Si K-edges, active Ga species are incorporated in H-MFI frameworks with T d symmetry. Local structure around Ga is very stable but distorted Si O 4 local structure can be formed after NO x -SCR reaction with CH 4 .Zeolites are well known as microporous materials, and have been applied widely to several engineering processes because of surface activity resulting from acidity. Zeolites are open framework aluminosilicates consisting of SiO 4 and AlO 4 , interconnected via oxygen atoms, and both Si and Al are present with T d symmetry in the framework. Distortion of T d sites (SiO 4 and AlO 4 ) is often brought about by application of several thermal processes or reactions. MFI zeolites are typical catalysts with unique activity for several useful reactions. In particular, Cu 2+ ion-exchanged H-MFI shows high deNO x activity with hydrocarbons. 1,2 For ion-exchanged zeolite catalysts, significant problems due to hydrothermal stability cannot be avoided in the case of modified MFI. On the other hand, metallosilicates are an appropriate material because active transition-metal ions are incorporated onto the framework. 3 For example, Fe 3+ -substituted MOR zeolites show high NO-SCR activity for methane. 4 But deactivation during the reaction is a major issue. We synthesized Fe-and Ga-MFI with various metal ratios by hydrothermal synthesis. Fe 3+ -and Ga 3+ -cosubstituted MFI (FeGaMFI) can be obtained. These materials show unique reactivity for NO x -SCR. 5 FeMFI with high Fe ratio shows high NO CH 4 reactivity, while no activity for NO x -SCR in the presence of O 2 . In contrast, GaO x is an appropriate component for NO x -SCR. It has been reported that Ga 2 O 3 Al 2 O 3 catalyst systems show high NO x -SCR activity. 6 Ga ion-exchanged H-MFI is also a widely-known catalyst for NO x -SCR with methane, as reported by Kikuchi et al. 7 and Inui et al. 8 Ga species on H-MFI show high and selective activity for NO x -SCR, but Ga modification brings about low acidity of H-MFI support because of coverage of non-framework Ga ions on the strong acid sites. 9 The NO x -SCR reactivity is likely to relate to the formation rate of NO 2 , and thus the acidity of Gamodified H-MFI is important to oxidize NO to NO 2 . In order to design useful and robust NO x -SCR catalysts, Ga-incorporated MFI metallosilicates (gallosilicates: GaMFI) are attractive because of stronger acidity than Ga ion-exchanged MFI. 9,10 Therefore, both the strong acidity and structural stabil...

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8.1.6.8 Zeolites having mordenite-, ferrierite-, boggsite-, epistilbite-, and terranovaite-type framework

Burzo

2013

Tectosilicates

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Cited by 9 publications

References 7 publications

Local Structure of Framework Iron in Fe-Substituted Al-Mordenites by Fe K Edge XAFS

Local Structure of Framework Iron in Fe-Substituted Al-Mordenites by Fe K Edge XAFS

Gallosilicate-Based Catalysts for NOx-SCR with CH4

8.1.6.8 Zeolites having mordenite-, ferrierite-, boggsite-, epistilbite-, and terranovaite-type framework

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