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Mechanism and micro-kinetics of direct N2O decomposition over BaFeAl11O19 hexaaluminate and comparison with Fe-MFI zeolites

Paper ID Volume ID Publish Year Pages File Format Full-Text
47211 46464 2010 8 PDF Available
Title
Mechanism and micro-kinetics of direct N2O decomposition over BaFeAl11O19 hexaaluminate and comparison with Fe-MFI zeolites
Abstract

Mechanistic and kinetic aspects of direct N2O decomposition over BaFeAl11O19 hexaaluminate were investigated in the Temporal Analysis of Products (TAP) reactor and compared with those previously determined for Fe-MFI zeolites. The catalysts were chosen due to their de-N2O operation in significantly different temperature regimes. Several micro-kinetic models were evaluated for describing the transient responses of N2O, N2, and O2 obtained in N2O pulse experiments at 823–973 K. Thorough discrimination between these models enabled us to conclude that the preferred models of N2O decomposition over BaFeAl11O19 and Fe-MFI zeolites differ in the reaction pathways leading to O2 and N2. Gas-phase N2 and O2 are simultaneously formed over BaFeAl11O19 upon interaction of gas-phase N2O with a bi-atomic surface oxygen (*–O2) species. Contrarily, the formation of O2 over Fe-MFI occurs via a sequence of three elementary heterogeneous steps and limits the overall rate of N2O decomposition. Despite the easy O2 formation, BaFeAl11O19 is less active for N2O decomposition below 973 K than the Fe-MFI zeolites due to the low coverage by *–O2. According to our quantitative micro-kinetic analysis, this species is formed when gas-phase N2O reacts with a mono-atomic oxygen (*–O) species. This reaction pathway is strongly influenced by the degree of isolation of iron species. The higher the degree of iron isolation in the catalyst, the lower the de-N2O activity.

Graphical abstractFigure optionsDownload full-size imageDownload as PowerPoint slideResearch highlights▶ Micro-kinetic origins of distinct de-N2O activity of BaFeAl11O19 and Fe-MFI catalysts were established from kinetic evaluation of transient experiments in the TAP reactor. ▶ The derived micro-kinetics of N2O decomposition can be extrapolated to higher pressures. ▶ It correctly predicts the differences in steady-state performance. ▶ The de-N2O activity is influenced by the collision frequency of N2O with *-O species.

Keywords
N2O decomposition; Iron hexaaluminate; Fe-ZSM-5; Oxygen formation; Mechanism; Micro-kinetics; TAP reactor
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Mechanism and micro-kinetics of direct N2O decomposition over BaFeAl11O19 hexaaluminate and comparison with Fe-MFI zeolites
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Publisher
Database: Elsevier - ScienceDirect
Journal: Applied Catalysis B: Environmental - Volume 99, Issues 1–2, 31 August 2010, Pages 66–73
Authors
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Subjects
Physical Sciences and Engineering Chemical Engineering Catalysis
Get Full-Text Now
Don't Miss Today's Special Offer
Price was $35.95
You save - $31
Price after discount Only $4.95
100% Money Back Guarantee
Full-text PDF Download
Online Support
Any Questions? feel free to contact us