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Journal of Catalysis
Volume 220, Issue 2, 10 December 2003, Pages 500-512
 
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doi:10.1016/j.jcat.2003.08.009    
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Copyright © 2003 Elsevier Inc. All rights reserved.

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

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Marijke H. Groothaert, Kristof Lievens, Hugo Leeman, Bert M. Weckhuysen and Robert A. SchoonheydtCorresponding Author Contact Information, E-mail The Corresponding Author

Center for Surface Chemistry and Catalysis, K.U. Leuven, Kasteelpark Arenberg 23, B-3001, Leuven, Belgium


Received 16 April 2003; 
revised 12 August 2003; 
accepted 12 August 2003. ;
Available online 24 October 2003.

Abstract

The role of the bis(μ-oxo)dicopper core, i.e., [Cu2(μ-O)2]2+, in the decomposition of NO and N2O 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. Measurement under transient reaction conditions indicated that [Cu2(μ-O)2]2+ is formed by O abstraction of N2O, which is an intermediate in the NO decomposition. This conversion of N2O to N2 and O2 is strongly retarded below 673 K. Above 673 K, the produced [Cu2(μ-O)2]2+ fulfills the role of O2 release, guaranteeing the self-reduction of the catalytic site. Studying the NO decomposition as a function of the O2 content in the feed strongly suggested that O2 release from [Cu2(μ-O)2]2+ is rate limiting in the NO decomposition at 773 K.

Author Keywords: Cu-ZSM-5; bis(μ-oxo)dicopper; NO decomposition; N2O decomposition; UV–vis spectroscopy; Operando spectroscopy

Article Outline

1. Introduction
2. Experimental section
2.1. Samples
2.2. Catalytic testing
2.3. Operando UV–vis spectroscopy
3. Results
3.1. O2-activated Cu-ZSM-5 and temperature dependence of the CT band positions
3.2. Time and temperature dependence of the NO decomposition
3.3. NO decomposition activity as a function of the copper content of Cu-ZSM-5
3.4. NO decomposition activity as a function of the O2 content in the feed
3.5. Temperature dependence of the N2O decomposition
3.6. N2O decomposition activity as a function of the O2 content in the feed
3.7. N2O decomposition during temperature drop
4. Discussion
4.1. Bis(μ-oxo)dicopper formed by O abstraction of N2O
4.2. O2 release from bis(μ-oxo)dicopper
4.3. The reaction cycle for NO decomposition
4.4. The reaction cycle for N2O decomposition
5. Conclusions
Acknowledgements
References













Corresponding Author Contact InformationCorresponding author.


Journal of Catalysis
Volume 220, Issue 2, 10 December 2003, Pages 500-512
 
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