A look into the surface chemistry of N2O decomposition on iron zeolites by transient response experiments

Pirngruber, Gerhard D.; Roy, Pijus K.

doi:10.1016/j.cattod.2005.09.023

Cited by 35 publications

(31 citation statements)

References 54 publications

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“…As a result we concluded that the pre-treatment of the zeolite affects the surface oxygen formation. Moreover, we found further evidence that different surface oxygen species exist which differ in thermal stability and reactivity, in agreement to results of other groups [8,13,16,[20][21][22][23]32].…”

Section: Introductionsupporting

confidence: 92%

“…This result dissents the findings of Jia et al [13] and Pirngruber and co-workers [20][21][22][23] who did not observe an isotopic exchange of surface oxygen without a special pre-treatment of the ZSM5 zeolites containing similar iron amounts. The reason for this discrepancy might be the different method of iron introduction through chemical vapour deposition with FeCl 3 , which provides different iron species.…”

Section: Static Vacuum Techniquesupporting

confidence: 82%

“…(1)), where an atomic, surface bound oxygen species is formed during the interaction of N 2 O with active iron sites in the zeolite Z [9][10][11][12][13][14][15][16][17][18][19][20][21][22][23][24][25]. This step initiates not only the stoichiometric N 2 O decomposition to nitrogen and oxygen, but also provides a selective oxygen species called "␣-oxygen" by Panov and co-workers [3,4,[9][10][11][12].…”

Section: Introductionmentioning

confidence: 99%

“…It is generally questionable if these results can be used for kinetic and mechanistic interpretations of results obtained under technically relevant conditions slightly above ambient pressure. Therefore, several transient response techniques have also been applied under atmospheric pressure [16][17][18][19][20][21][22][23][24][25], sometimes combined with subsequent temperature-programmed desorption of the surface bound species as well as with isotopic labelling experiments [21,22].…”

Section: Introductionmentioning

confidence: 99%

“…The same experiments were also performed at 673 K, above the lightoff temperature of the total N 2 O decomposition, with zeolites containing high iron amounts (3.5-4.5% Fe, w/w) [20][21][22][23]. In addition, Wood et al [19] have shown that step experiments are suitable to determine the kinetics of the surface oxygen formation.…”

Section: Introductionmentioning

confidence: 99%

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Experimental techniques for investigating the surface oxygen formation in the N2O decomposition on Fe-MFI zeolites

Ateş¹,

Reitzmann²

2007

Chemical Engineering Journal

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Several experimental techniques were used to investigate the formation of surface oxygen in the N 2 O decomposition on an Fe-MFI zeolite. These techniques consisted of multipulse and step experiments as transient methods at ambient pressure and experiments in a closed set-up of Panov and co-workers at strongly reduced pressure. The total amount of surface oxygen determined through multipulse experiments was in the range of the amount obtained in the vacuum set-up at 523 K (40-50 mol O g −1 catalyst ). In contrast, the step technique revealed considerably higher values, up to 110 mol O g −1 catalyst , indicating an accumulation of oxygen in the zeolite. This phenomenon might also be responsible for the observation that higher reaction temperatures increase the total amount of surface oxygen, which can be deposited in the zeolite. In contrast to experiments in the vacuum set-up, the temperature-programmed desorption after multipulse and step experiments shows the presence of various oxygen species differing in thermal stability. The influence of temperature on the rate of surface oxygen formation was determined from step and vacuum experiments. The results of the step experiments lead to a lower activation energy, 14 kJ mol −1 , than the experiments in the vacuum set-up (49 kJ mol −1 ), probably due to sorption and mass transfer effects. Comparing the rate of surface oxygen formation and of total N 2 O decomposition reveals that the former is very fast and not rate determining for the latter. Furthermore, the rate of total N 2 O decomposition seems to be inhibited by adsorbed N 2 O, detected in the transient experiments. This observation is considered in an adequate kinetic model.

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Section: Introductionsupporting

confidence: 92%

Section: Static Vacuum Techniquesupporting

confidence: 82%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Experimental techniques for investigating the surface oxygen formation in the N2O decomposition on Fe-MFI zeolites

Ateş¹,

Reitzmann²

2007

Chemical Engineering Journal

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N₂O Decomposition over Fe‐ZSM‐5 Studied by Transient Techniques

et al. 2009

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The observed rate increase is assigned to a slow accumulation on the surface of NO x,ads species formed from N 2 O and participating as co-catalyst in the N 2 O decomposition. The NO x,ads species accelerates the atomic oxygen recombination/ desorption, which is the rate-determining step of N 2 O decomposition. The formation and accumulation of NO x,ads species during N 2 O interaction with the catalyst was confirmed by TAP studies. The amount of NO x,ads was found to depend on the number of N 2 O pulses injected into the TAP reactor. In the presence of adsorbed NO x on the catalyst surface (NO x,ads ) the desorption of dioxygen is facilitated. This results in a shift of the oxygen desorption temperature from 744 K to considerably lower temperatures of 580 K in TPD experiments. Pulses of gaseous NO had a similar effect leading to the formation NO x,ads , thus facilitating the oxygen recombination/desorption.

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Theoretical Study of N₂O Reduction by CO in Fe‐BEA Zeolite

et al. 2006

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Quantum mechanical (QM) and QM/molecular mechanics (MM) studies of the full catalytic cycle of N(2)O reduction by CO in Fe-BEA zeolite, that is, oxidation of BEA-Fe by N(2)O and reduction of BEA-Fe-alphaO by CO, is presented. A large QM cluster, representing half of the channel of the BEA zeolite, is used. The contribution of the MM embedding to the calculated activation energies is found to be negligible. The minimum-energy paths for N(2)O decomposition and reduction with CO are calculated using the nudged elastic band (NEB) method. Calculated and experimental activation energies are in good agreement. The two possible orientations for the gaseous molecules adsorbing on the Fe site that are found lead to different activation energies.

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A look into the surface chemistry of N2O decomposition on iron zeolites by transient response experiments

Cited by 35 publications

References 54 publications

Experimental techniques for investigating the surface oxygen formation in the N2O decomposition on Fe-MFI zeolites

Experimental techniques for investigating the surface oxygen formation in the N2O decomposition on Fe-MFI zeolites

N₂O Decomposition over Fe‐ZSM‐5 Studied by Transient Techniques

Theoretical Study of N₂O Reduction by CO in Fe‐BEA Zeolite

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A look into the surface chemistry of N2O decomposition on iron zeolites by transient response experiments

Cited by 35 publications

References 54 publications

Experimental techniques for investigating the surface oxygen formation in the N2O decomposition on Fe-MFI zeolites

Experimental techniques for investigating the surface oxygen formation in the N2O decomposition on Fe-MFI zeolites

N2O Decomposition over Fe‐ZSM‐5 Studied by Transient Techniques

Theoretical Study of N2O Reduction by CO in Fe‐BEA Zeolite

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Product

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N₂O Decomposition over Fe‐ZSM‐5 Studied by Transient Techniques

Theoretical Study of N₂O Reduction by CO in Fe‐BEA Zeolite