Mechanisms behind sulfur promoted oxidation of methane
Journal article, 2013
The promoting effect of SO2 on the activity for methane oxidation over platinum supported on silica, alumina and ceria has been studied by flow-reactor, in situ infrared spectroscopy and in situ high-energy x-ray diffraction experiments under transient reaction conditions. The catalytic activity is clearly dependent on the support material and its interaction with the noble metal both in absence and presence of sulfur. On platinum, the competitive reactant adsorption favors oxygen dissociation such that oxygen self-poisoning is observed for Pt/silica and Pt/alumina. Contrarily for Pt/ceria, no oxygen self-poisoning is observed, which seems to be due to additional reaction channels via sites on the platinum-ceria boundary and/or ceria surface considerably far from the Pt crystallites. Addition of sulfur dioxide generally leads to the formation of ad-SOx species on the supports with a concomitant removal and/or blockage/rearrangement of surface hydroxyl groups. Thereby, the methane oxidation is inhibited for Pt/silica, enhanced for Pt/alumina and temporary enhanced followed by inhibition after long-term exposure to sulfur for Pt/ceria. The observations can be explained by competitive oxidation of SO2 and CH4 on Pt/silica, formation of new active sites at the noble metal-support interface promoting dissociative adsorption of methane on Pt/alumina, and in the case of Pt/ceria, formation of promoting interfacial surface sulfates followed by formation of deactivating bulk-like sulfate species. Furthermore, it can be excluded that reduction of detrimental high oxygen coverage and/or oxide formation on the platinum particles through SO2 oxidation is the main cause for the promotional effects observed.
Author
Djamela Bounechada
Chalmers, Chemical and Biological Engineering, Applied Surface Chemistry
Competence Centre for Catalysis (KCK)
Sheedeh Fouladvand
Chalmers, Chemical and Biological Engineering, Applied Surface Chemistry
Competence Centre for Catalysis (KCK)
Torben Pingel
Competence Centre for Catalysis (KCK)
Chalmers, Applied Physics, Eva Olsson Group
Lisa Kylhammar
Chalmers, Chemical and Biological Engineering, Applied Surface Chemistry
Competence Centre for Catalysis (KCK)
Eva Olsson
Chalmers, Applied Physics, Eva Olsson Group
Competence Centre for Catalysis (KCK)
Magnus Skoglundh
Competence Centre for Catalysis (KCK)
Chalmers, Chemical and Biological Engineering, Applied Surface Chemistry
Johan Gustafsson
Lund University
Marco Di Michiel
European Synchrotron Radiation Facility (ESRF)
Mark Newton
European Synchrotron Radiation Facility (ESRF)
Per-Anders Carlsson
Competence Centre for Catalysis (KCK)
Chalmers, Chemical and Biological Engineering, Applied Surface Chemistry
Physical Chemistry Chemical Physics
1463-9076 (ISSN) 1463-9084 (eISSN)
Vol. 15 22 8648-8661Catalysts for demanding environments
Swedish Foundation for Strategic Research (SSF) (RMA08-0085), 2009-07-01 -- 2013-06-30.
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Chalmers Materials Analysis Laboratory
DOI
10.1039/c3cp44289f