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Sites for methane activation on lithium-doped magnesium oxide surfaces
Publikationstyp
Journal Article
Date Issued
2014-08-11
Sprache
English
Author(s)
Kwapien, Karolina
Paier, Joachim
Sauer, Joachim
Zavyalova, Ulyana
Schwach, Pierre
Trunschke, Annette
Volume
53
Issue
33
Start Page
8774
End Page
8778
Citation
Angewandte Chemie - International Edition 53 (33): 8774-8778 (2014)
Publisher DOI
Scopus ID
Publisher
Wiley
Density functional calculations yield energy barriers for H abstraction by oxygen radical sites in Li-doped MgO that are much smaller (12±6 kJmol-1) than the barriers inferred from different experimental studies (80-160 kJmol-1). This raises further doubts that the Li +O.- site is the active site as postulated by Lunsford. From temperature-programmed oxidative coupling reactions of methane (OCM), we conclude that the same sites are responsible for the activation of CH 4 on both Li-doped MgO and pure MgO catalysts. For a MgO catalyst prepared by sol-gel synthesis, the activity proved to be very different in the initial phase of the OCM reaction and in the steady state. This was accompanied by substantial morphological changes and restructuring of the terminations as transmission electron microscopy revealed. Further calculations on cluster models showed that CH4 binds heterolytically on Mg2+O 2- sites at steps and corners, and that the homolytic release of methyl radicals into the gas phase will happen only in the presence of O 2. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.
Subjects
active sites
C-H activation
density functional calculations
Li-doped MgO
magnesium oxide
DDC Class
540: Chemistry