On the nature of active sites in Fe/ZSM-5 catalysts for NO(χ) abatement

Timur V. Voskoboinikov; Hai Ying Chen; Wolfgang M.H. Sachtler

doi:10.1016/S0926-3373(98)00082-4

On the nature of active sites in Fe/ZSM-5 catalysts for NO(χ) abatement

Timur V. Voskoboinikov, Hai Ying Chen, Wolfgang M.H. Sachtler

Research output: Contribution to journal › Article › peer-review

150 Scopus citations

Abstract

Fe/ZSM-5 catalysts with high Fe loading (Fe/Al~1) have been prepared by sublimation of FeCl₃ onto H-ZSM-5 samples of different Si/Al ratios. They catalyze NO(χ) reduction with hydrocarbons in an excess of O₂ and H₂O. TPR shows that the Fe in the zeolite cavities is different from Fe₂O₃ particles. Naked Fe³⁺ ions are absent; oxo-ions, which are equally well reducible by CO and H₂, prevail. A minority of the Fe complexes lose oxygen upon mere heating to ~500°C; some of the reduced sites are reoxidized only by N₂O. The population of oxo-complexes that lose oxygen by heating depends on the Si/Al ratio, this dependence is in qualitative agreement with the model of (2+) charged binuclear ions [HO-Fe-O-Fe-OH]²⁺. Upon reacting with NO, the bridging O atom is transferred and NO₂ is formed. This step is not rate limiting for active catalysts with high Al/Si ratio and high Fe loading, but it becomes critical with zeolites of low Al/Si ratio.

Original language	English
Pages (from-to)	279-287
Number of pages	9
Journal	Applied Catalysis B: Environmental
Volume	19
Issue number	3-4
DOIs	https://doi.org/10.1016/S0926-3373(98)00082-4
State	Published - Dec 7 1998
Externally published	Yes

Funding

Financial support of this research by an unrestricted grant from the Ford Motor Corporation is gratefully acknowledged. We also thank Dr. Steve Wilson at UOP and Dr. Karin Bartels at Degussa for kindly donating us ZSM-5 samples.

Keywords

Active sites
Fe/ZSM-5
SCR of NO
Si/Al ratio
Thermal reduction

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10.1016/S0926-3373(98)00082-4

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title = "On the nature of active sites in Fe/ZSM-5 catalysts for NO(χ) abatement",

abstract = "Fe/ZSM-5 catalysts with high Fe loading (Fe/Al\textasciitilde{}1) have been prepared by sublimation of FeCl3 onto H-ZSM-5 samples of different Si/Al ratios. They catalyze NO(χ) reduction with hydrocarbons in an excess of O2 and H2O. TPR shows that the Fe in the zeolite cavities is different from Fe2O3 particles. Naked Fe3+ ions are absent; oxo-ions, which are equally well reducible by CO and H2, prevail. A minority of the Fe complexes lose oxygen upon mere heating to \textasciitilde{}500°C; some of the reduced sites are reoxidized only by N2O. The population of oxo-complexes that lose oxygen by heating depends on the Si/Al ratio, this dependence is in qualitative agreement with the model of (2+) charged binuclear ions [HO-Fe-O-Fe-OH]2+. Upon reacting with NO, the bridging O atom is transferred and NO2 is formed. This step is not rate limiting for active catalysts with high Al/Si ratio and high Fe loading, but it becomes critical with zeolites of low Al/Si ratio.",

keywords = "Active sites, Fe/ZSM-5, SCR of NO, Si/Al ratio, Thermal reduction",

author = "Voskoboinikov, \{Timur V.\} and Chen, \{Hai Ying\} and Sachtler, \{Wolfgang M.H.\}",

year = "1998",

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doi = "10.1016/S0926-3373(98)00082-4",

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T1 - On the nature of active sites in Fe/ZSM-5 catalysts for NO(χ) abatement

AU - Voskoboinikov, Timur V.

AU - Chen, Hai Ying

AU - Sachtler, Wolfgang M.H.

PY - 1998/12/7

Y1 - 1998/12/7

N2 - Fe/ZSM-5 catalysts with high Fe loading (Fe/Al~1) have been prepared by sublimation of FeCl3 onto H-ZSM-5 samples of different Si/Al ratios. They catalyze NO(χ) reduction with hydrocarbons in an excess of O2 and H2O. TPR shows that the Fe in the zeolite cavities is different from Fe2O3 particles. Naked Fe3+ ions are absent; oxo-ions, which are equally well reducible by CO and H2, prevail. A minority of the Fe complexes lose oxygen upon mere heating to ~500°C; some of the reduced sites are reoxidized only by N2O. The population of oxo-complexes that lose oxygen by heating depends on the Si/Al ratio, this dependence is in qualitative agreement with the model of (2+) charged binuclear ions [HO-Fe-O-Fe-OH]2+. Upon reacting with NO, the bridging O atom is transferred and NO2 is formed. This step is not rate limiting for active catalysts with high Al/Si ratio and high Fe loading, but it becomes critical with zeolites of low Al/Si ratio.

AB - Fe/ZSM-5 catalysts with high Fe loading (Fe/Al~1) have been prepared by sublimation of FeCl3 onto H-ZSM-5 samples of different Si/Al ratios. They catalyze NO(χ) reduction with hydrocarbons in an excess of O2 and H2O. TPR shows that the Fe in the zeolite cavities is different from Fe2O3 particles. Naked Fe3+ ions are absent; oxo-ions, which are equally well reducible by CO and H2, prevail. A minority of the Fe complexes lose oxygen upon mere heating to ~500°C; some of the reduced sites are reoxidized only by N2O. The population of oxo-complexes that lose oxygen by heating depends on the Si/Al ratio, this dependence is in qualitative agreement with the model of (2+) charged binuclear ions [HO-Fe-O-Fe-OH]2+. Upon reacting with NO, the bridging O atom is transferred and NO2 is formed. This step is not rate limiting for active catalysts with high Al/Si ratio and high Fe loading, but it becomes critical with zeolites of low Al/Si ratio.

KW - Active sites

KW - Fe/ZSM-5

KW - SCR of NO

KW - Si/Al ratio

KW - Thermal reduction

UR - https://www.scopus.com/pages/publications/0032495115

U2 - 10.1016/S0926-3373(98)00082-4

DO - 10.1016/S0926-3373(98)00082-4

M3 - Article

AN - SCOPUS:0032495115

SN - 0926-3373

VL - 19

SP - 279

EP - 287

JO - Applied Catalysis B: Environmental

JF - Applied Catalysis B: Environmental

IS - 3-4

ER -

On the nature of active sites in Fe/ZSM-5 catalysts for NO(χ) abatement

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