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Effect of large cations (La3+ and Ba2+) on the catalytic performance of Mn-substituted hexaaluminates for N2O decomposition

Paper ID Volume ID Publish Year Pages File Format Full-Text
47582 46476 2009 8 PDF Available
Title
Effect of large cations (La3+ and Ba2+) on the catalytic performance of Mn-substituted hexaaluminates for N2O decomposition
Abstract

Mn-substituted La-hexaaluminate (LaMnxAl(12−x)O19) and Ba-hexaaluminate (BaMnxAl(12−x)O19) catalysts were prepared using the carbonates route and investigated for high-concentration of N2O decomposition. It was for the first time found that the Ba-hexaaluminate exhibited higher activity than the La-hexaaluminate at a given Mn content, both of which were much more active than Mn/Al2O3 after being subjected to high-temperature (1400 °C) treatment. The catalytic activity varied with the Mn content and attained the best one at x = 1. X-ray diffraction (XRD) characterizations showed that a small amount of Mn (up to x = 1) promoted greatly the formation of phase-pure hexaaluminate, while excess Mn caused formation of catalytically inactive impurity phases, such as LaAlO3, BaAl2O4, Mn3O4, and LaMnO3, which covered partially the active sites and then led to a loss of the activity. UV–visible spectra showed that Mn2+ preferentially enter tetrahedral Al sites at a low Mn content (x = 0.5) for the La-hexaaluminate, which is quite different from the case of Ba-hexaaluminate where Mn3+ can substitute octahedral Al sites even at x = 0.5. Such a difference in the number of catalytically active Mn3+ sites in the octahedral position should be responsible for the higher activity of the Mn-substituted Ba-hexaaluminate.

Keywords
N2O decomposition; Propellant; Manganese; Hexaaluminate
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Effect of large cations (La3+ and Ba2+) on the catalytic performance of Mn-substituted hexaaluminates for N2O decomposition
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Publisher
Database: Elsevier - ScienceDirect
Journal: Applied Catalysis B: Environmental - Volume 92, Issues 3–4, 9 November 2009, Pages 437–444
Authors
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Subjects
Physical Sciences and Engineering Chemical Engineering Catalysis
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Price was $35.95
You save - $31
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