The role of monomeric iron during the selective catalytic reduction of NOx by NH3 over Fe-BEA zeolite catalysts

Høj, Martin; Beier, Matthias; Grunwaldt, Jan‐Dierk; Dahl, Søren

doi:10.1016/j.apcatb.2009.09.026

Cited by 114 publications

(95 citation statements)

References 41 publications

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“…For instance, high loadings of Fe result in haematite-like aggregates with high surface area, whereas low contents of iron lead to highly dispersed iron oxide entities [9]. For SCR, it is wellknown that the catalytic activity is closely related to the number of Fe sites with high dispersion, particularly isolated centres and oligonuclear clusters [19,20], whereas strongly aggregated moieties reveal rather little activity [4,10]. Furthermore, the interaction of the Fe sites with respective substrate also affects catalytic efficiency, for instance in low-and high-temperature SCR [21].…”

Section: Introductionmentioning

confidence: 99%

Towards advanced structural analysis of iron oxide clusters on the surface of γ-Al2O3 using EXAFS

Boubnov

Roppertz

Kundrat

et al. 2016

Applied Surface Science

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Section: Introductionmentioning

confidence: 99%

Towards advanced structural analysis of iron oxide clusters on the surface of γ-Al2O3 using EXAFS

Boubnov

Roppertz

Kundrat

et al. 2016

Applied Surface Science

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“…Below 300 °C, only monomeric Fe species contributed to the SCR reaction, and this type of Fe species did not catalyze the NH 3 unselective oxidation below 500 °C, which was beneficial to high N 2 selectivity [42]. The important role of monomeric Fe 3+ sites was also emphasized by Høj et al [43] in their Fe-BEA catalysts. The UV-Vis DRS, EPR and XAS results by Høj et al [43] suggested that low Fe loadings (≤1.2 wt.% Fe) could result in mostly iron monomers in Fe-BEA catalysts, especially for the ion-exchanged samples.…”

Section: Active Sites Of Fe-zeolite Catalysts In the Nh 3 -Scr Reactionmentioning

confidence: 92%

“…The important role of monomeric Fe 3+ sites was also emphasized by Høj et al [43] in their Fe-BEA catalysts. The UV-Vis DRS, EPR and XAS results by Høj et al [43] suggested that low Fe loadings (≤1.2 wt.% Fe) could result in mostly iron monomers in Fe-BEA catalysts, especially for the ion-exchanged samples. However, a mixture of monomers, oligomers and Fe 2 O 3 particles would form at medium to high loadings (such as 2.5-5.1 wt.% Fe).…”

Section: Active Sites Of Fe-zeolite Catalysts In the Nh 3 -Scr Reactionmentioning

confidence: 94%

Emerging Applications of Environmentally Friendly Zeolites in the Selective Catalytic Reduction of Nitrogen Oxides

Xie

Shi

2016

Green Chemistry and Sustainable Technology

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The catalytic removal of nitrogen oxides (NO x ) from diesel exhaust under oxygen-rich conditions remains a major challenge in the field of environmental catalysis, and the selective catalytic reduction of NO x with NH 3 (NH 3 -SCR), especially over zeolite catalysts, is a well-proven technique for the catalytic deNO x process for diesel vehicles. The comprehensive understanding of the structure-activity relationship of zeolite catalysts in the NH 3 -SCR reaction and the elucidation of the detailed reaction mechanism are very important for the practical use of these catalytic materials. In this chapter, using the environmentally friendly Fe-and Cu-based zeolite catalysts (i.e. Fe-ZSM-5, Cu-ZSM-5, Cu-SSZ-13 and Cu-SAPO-34, etc.) as examples, the influence of preparation methods on NH 3 -SCR performance, the role of metal active sites/surface acid sites, the impact of NO 2 and co-existing pollutants, the hydrothermal stability and also the possible SCR reaction pathways over these materials are discussed in detail, which can provide theoretical and empirical guidance for the redesign and activity improvement of these catalysts in their practical applications.

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“…Fe active sites are involved in the NO oxidation to NO2, which is considered the slow step of the SCR reaction [22,27]. Among the various types of Fe species coexisting in the Fe-ZSM-5 catalysts, the isolated Fe 3+ species are considered to contribute to the SCR reaction at low temperatures (< 300 °C) [23,28,29]. Therefore, the higher SCR activity of Fe-HZ might be mainly attributed to the higher amount of active Fe 3+ ions and the greater number of Brønsted acid sites in this catalyst compared with those in Fe-NaZ.…”

Section: Discussionmentioning

confidence: 99%

The effect of Fe species distribution and acidity of Fe-ZSM-5 on the hydrothermal stability and SO2 and hydrocarbons durability in NH3-SCR reaction

Shi

Xie

2015

Chinese Journal of Catalysis

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Fe-exchanged ZSM-5 catalysts prepared from Na ＋ and H ＋ forms of ZSM-5 were evaluated for the selective catalytic reduction of NOx by NH3 (NH3-SCR). Fe-H-ZSM-5 showed higher SCR activity than Fe-Na-ZSM-5 both when fresh and after hydrothermal aging at 750 °C in 5% H2O/air. The Fe species distribution and acidity of Fe-H-ZSM-5 and Fe-Na-ZSM-5 were found to be different. The dealumination of the zeolite framework of Fe-H-ZSM-5 during hydrothermal aging was found to be more severe compared with that of Fe-Na-ZSM-5. The durability of Fe-H-ZSM-5 and Fe-Na-ZSM-5 in NH3-SCR was compared using SO2 tolerance and hydrocarbon resistance experiments. The effect of water and SO2 on the activity of the two catalysts was similar, such that their activity decreased at low temperatures and increased at high temperatures. Fe-Na-ZSM-5 showed better propene resistance than Fe-H-ZSM-5. The SO2 and propene poisoning of the two Fe-ZSM-5 catalysts were found to be reversible.

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The role of monomeric iron during the selective catalytic reduction of NOx by NH3 over Fe-BEA zeolite catalysts

Cited by 114 publications

References 41 publications

Towards advanced structural analysis of iron oxide clusters on the surface of γ-Al2O3 using EXAFS

Towards advanced structural analysis of iron oxide clusters on the surface of γ-Al2O3 using EXAFS

Emerging Applications of Environmentally Friendly Zeolites in the Selective Catalytic Reduction of Nitrogen Oxides

The effect of Fe species distribution and acidity of Fe-ZSM-5 on the hydrothermal stability and SO2 and hydrocarbons durability in NH3-SCR reaction

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