Characterization of LaMnAl11O19 by FT-IR spectroscopy of adsorbed NO and NO/O2
Date
2005-12-15Source Title
Applied Surface Science
Print ISSN
0169-4332
Publisher
Elsevier
Volume
252
Issue
5
Pages
1481 - 1491
Language
English
Type
ArticleItem Usage Stats
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Abstract
The nature of the NOx species produced during the adsorption of NO at room temperature and during its coadsorption with
oxygen on LaMnAl11O19 sample with magnetoplumbite structure obtained by a sol–gel process has been investigated by means
of in situ FT-IR spectroscopy. The adsorption of NO leads to formation of anionic nitrosyls and/or cis-hyponitrite ions and
reveals the presence of coordinatively unsaturated Mn3+ ions. Upon NO/O2 adsorption at room temperature various nitro–nitrato
structures are observed. The nitro–nitrato species produced with the participation of electrophilic oxygen species decompose at
350 8C directly to N2 and O2. No NO decomposition is observed in absence of molecular oxygen. The adsorbed nitro–nitrato
species are inert towards the interaction with methane and block the active sites (Mn3+ ions) for its oxidation. Noticeable
oxidation of the methane on the NOx -precovered sample is observed at temperatures higher than 350 8C due to the liberation of
the active sites as a result of decomposition of the surface nitro–nitrato species. Mechanism explaining the promoting effect of
the molecular oxygen in the NO decomposition is proposed.
(c)2005 Elsevier B.V. All rights reserved.
Keywords
LaMnAl11O19Sol - gel synthesis
In situ FT - IR spectroscopy
Adsorption of NO and NO/O2
Reactivity of stable NOx species
NO decomposition