Title: Dynamic Cu/Zn Interaction in SiO2 Supported Methanol Synthesis Catalysts Unraveled by in Situ XAFS
Authors: Grandjean, Didier ×
Pelipenko, V.
Batyrev, E. D.
van den Heuvel, J. C.
Khassin, A. A.
Yurieva, T. M.
Weckhuysen, B. M. #
Issue Date: Oct-2011
Publisher: American Chemical Society
Series Title: Journal of Physical Chemistry C vol:115 issue:41 pages:20175-20191
Abstract: In situ X-ray absorption spectroscopy XAFS at the Cu and Zn K-edge has been used to unravel the Cu/Zn interaction and identify the possible active site of Cu-based methanol synthesis catalysts in the Cu/ZnO/SiO2 ternary system. These highly dispersed silica supported catalysts, whose activity increases sharply as a function of the reduction temperature, were studied calcined, reduced at 200, 300, and 400 degrees C, and for each reduction temperature under passivation/rereduction and methanol synthesis conditions. Results showed that the calcined form consists mainly of a mixed Cu/Zn hydrosilicate that is progressively transformed as the reduction temperature increases into (i) Cu metal particles, (ii) increasingly dispersed ZnO species on SiO2, and (iii) finally a Zn metallic phase forming segregated bimetallic Cu-Zn alpha-brass alloy particles. These different structures and Cu/Zn interfaces may correspond to different active phases and activities in methanol synthesis. After reduction at 200 and 300 degrees C, Cu-0 is likely composing most of the active phase, whereas above 300 degrees C, the sharp increase in the number Zn-0-based sites formed as a function of the reduction temperature could explain the major role played by this parameter in controlling the activity of these catalysts. The dynamic Cu/Zn interaction as a function of the temperature and gas environment pointed out in this ternary system may be at the origin of the existence of different and sometimes contradictory models to account for the mechanisms of the methanol synthesis.
ISSN: 1932-7447
Publication status: published
KU Leuven publication type: IT
Appears in Collections:Solid State Physics and Magnetism Section
× corresponding author
# (joint) last author

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