Catalytic decomposition of nitric oxide over Cu-zeolites

Li, Yuejin; Hall, W. Keith

doi:10.1016/0021-9517(91)90024-x

Cited by 376 publications

(125 citation statements)

References 13 publications

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“…This conclusion can be shared by our recent XANES and EXAFS results pointing to the presence of a considerable fraction of the bis(µ-oxo)dicopper core during NO decomposition [49]. The O 2 inhibition effect on the NO decomposition over Cu-ZSM-5 is well known and has been incorporated in the rate equation containing an [O 2 ] 1/2 term in the denominator [34,43]. In contrast, during N 2 O decomposition in the presence of an increased O 2 concentration, also an increase of bis(µ-oxo)dicopper core concentration was observed but no decrease of reaction rate was found.…”

Section: O 2 Release From Bis(µ-oxo)dicoppermentioning

confidence: 60%

“…Now, a growing consensus is found that monovalent copper participates in the NO decomposition reaction [27][28][29][30][31][32][33]. A number of experimental and computational studies propose a redox process cycling between Cu(I) and Cu(II)-ELO species (ELO, extralattice oxygen) [27][28][29][30][33][34][35][36][37][38]. However, the identity of the ELO is not clear.…”

Section: Introductionmentioning

confidence: 99%

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An operando optical fiber UV–vis spectroscopic study of the catalytic decomposition of NO and N2O over Cu-ZSM-5

Groothaert

Lievens

Leeman

et al. 2003

Journal of Catalysis

131

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The role of the bis(µ-oxo)dicopper core, i.e., [Cu 2 (µ-O) 2 ] 2+ , in the decomposition of NO and N 2 O by the Cu-ZSM-5 zeolite has been studied with combined operando UV-vis monitoring of the catalyst and on-line GC analysis. An optical fiber was mounted on the outer surface of the quartz wall of the plug-flow reactor and collected the UV-vis diffuse reflectance spectra under true catalytic conditions.

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Section: O 2 Release From Bis(µ-oxo)dicoppermentioning

confidence: 60%

Section: Introductionmentioning

confidence: 99%

An operando optical fiber UV–vis spectroscopic study of the catalytic decomposition of NO and N2O over Cu-ZSM-5

Groothaert

Lievens

Leeman

et al. 2003

Journal of Catalysis

131

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“…The monomolecular mechanism assumes that the rate determining step during the NO decomposition in zeolites is the activation of an adsorbed NO molecule. A slightly modified scheme of the mechanism proposed by Li and Hall 24 is presented in Figure 1. The first step is the desorption of oxygen from the zeolite lattice close to an adsorbed Cu 2+ ion.…”

Section: Substituting This Expression Formentioning

confidence: 99%

Theoretical Models for the Rate of NO Decomposition over Copper-Exchanged Zeolites

Tsekov

Smirniotis

1998

J. Phys. Chem. B

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A unified description of the catalytic effect of Cu-exchanged zeolites is proposed for the decomposition of NO. A general expression for the rate constant of NO decomposition is obtained by assuming that the rate-determining step consists of the transferring of a single atom associated with breaking of the N-O bond. The analysis is performed on the base of the generalized Langevin equation and takes into account both the potential interactions in the system and the memory effects due to the zeolite vibrations. Two different mechanisms corresponding to monomolecular and bimolecular NO decomposition are discussed. The catalytic effect in the monomolecular mechanism is related to both the Cu + ions and zeolite O-vacancies, while in the case of the bimolecular mechanism the zeolite contributes through dissipation only. The comparison of the theoretically calculated rate constants with experimental results reveals additional information about the geometric and energetic characteristics of the active centers and confirms the logic of the proposed models.Nitric oxides emitted by both mobile and stationary sources cause serious environmental problems. The demand of methods to reduce NO pollution has initiated intensive studies on NO degradation chemistry 1 . The most desirable process is to directly decompose the NO molecule to its elements, N2 and O2. This process is thermodynamically favorable, but its rate is very low. Thus, an important problem is to find active catalysts to substantially accelerate the reaction rate of NO decomposition. Several tests with well-known metal catalysts have demonstrated that they inefficiently catalyze NO decomposition; the catalysts are oxidized when the reaction progresses and finally the NO decomposition is inhibited. The most active catalysts for NO decomposition are ion-exchanged zeolites and primarily Cu-ZSM-5. These catalysts are prepared by introducing metal ions in zeolites via standard ion-exchange procedures 2 . Despite the large number of publications after the initial report of the catalytic activity of Cu-ZSM-5, there is still ongoing discussion about the catalytic mechanism. Iwamoto and Hamada 3 , as well as Hall and Valyon 4 , suggested that the active sites were Cu + ions rather than Cu 2+ . Hence, the copper redox chemistry 5 is of crucial importance for the catalytic performance. Selef 6 , however, has proposed that the square planar complex Cu 2+ (NO)2 is an alternative intermediate state responsible for the reaction. Kuroda et al. 7 have discovered an effect of O-bridged copper planar complexes while Shpiro et al. 8 have proposed that CuO clusters are the active catalytic centers. There is also no clear trend on the catalytic effect of the Si/Al ratio of zeolites. Moretti 9 reported that an increase of the Si/Al ratio leads to a decrease in catalytic activity thus indicating that the active centers

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“…The catalytic approaches for the removal of NO include (i) the reaction of NO with CO [1][2][3][4], (ii) selective catalytic reduction with NH 3 and hydrocarbons [5,6], and (iii) the direct decomposition of nitric oxide [7][8][9][10]. The advantages and disadvantages of each approach are listed in Table 1.…”

Section: Introductionmentioning

confidence: 99%

“…Studies on the proposed elementary steps for NO decomposition have revealed that the low activity of the catalysts is due to their inability to desorb oxygen produced from NO dissociation [8,10]. Oxygen from dissociated NO is strongly bonded to the catalyst surface, poisoning NO dissociation sites and inhibiting further NO dissociation.…”

Section: Introductionmentioning

confidence: 99%

In Situ Infrared Study of Catalytic Decomposition of No

Almusaiteer¹,

Krishnamurthy²,

Chuang³

1998

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The growing concerns for the environment and increasingly stringent standards for NO emission have presented a major challenge to control NO emissions from electric utility plants and automobiles. Catalytic decomposition of NO is the most attractive approach for the control of NO emission for its simplicity. Successful development of an effective catalyst for NO decomposition will greatly decrease the equipment and operation cost of NO control. Due to lack of understanding of the mechanism of NO decomposition, efforts on the search of an effective catalyst have been unsuccessful. Scientific development of an effective catalyst requires fundamental understanding of the nature of active site, the rate-limiting step, and an approach to prolong the life of the catalyst.Research is proposed to study the reactivity of adsorbates for the direct NO decomposition and to investigate the feasibility of two novel approaches for improving catalyst activity and resistance to sintering. The first approach is the use of silanation to stabilize metal crystallites and supports for Cu-ZSM-5 and promoted Pt catalysts; the second is utilization of oxygen spillover and desorption to enhance NO decomposition activity. An innovative infrared reactor system will be used to observe and determine the dynamic behavior and the reactivity of adsorbates during NO decomposition, oxygen spillover, and silanation. A series of experiments including X-ray diffraction, temperature programmed desorption, temperature programmed reaction, X-ray photoelectron spectroscopy will be used to characterized the catalysts. The information obtained from this study will provide a scientific basis for developing an effective catalyst for the NO decomposition under practical flue gas conditions.

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Catalytic decomposition of nitric oxide over Cu-zeolites

Cited by 376 publications

References 13 publications

An operando optical fiber UV–vis spectroscopic study of the catalytic decomposition of NO and N2O over Cu-ZSM-5

An operando optical fiber UV–vis spectroscopic study of the catalytic decomposition of NO and N2O over Cu-ZSM-5

Theoretical Models for the Rate of NO Decomposition over Copper-Exchanged Zeolites

In Situ Infrared Study of Catalytic Decomposition of No

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