Dynamic Cu/Zn Interaction in SiO2 Supported Methanol Synthesis Catalysts Unraveled by in Situ XAFS
Full article
| Общее |
Language:
Английский,
Genre:
Full article,
Status:
Published,
Source type:
Original
|
| Journal |
The Journal of Physical Chemistry C
ISSN: 1932-7447
, E-ISSN: 1932-7455
|
| Output data |
Year: 2011,
Volume: 115,
Number: 41,
Pages: 20175-20191
Pages count
: 17
DOI:
10.1021/jp201839s
|
| Authors |
Grandjean Didier
1,2
,
Pelipenko Vladimir
3
,
Batyrev Erdni D.
4
,
Heuvel Johannes C.van den
4
,
Khassin Alexander A.
3
,
Yurieva Tamara M.
3
,
Weckhuysen Bert M.
2
|
| Affiliations |
| 1 |
Laboratory of Solid State Physics and Magnetism & INPAC, K. U. Leuven, Celestijnenlaan 200D, B-3001, Leuven, Belgium
|
| 2 |
Inorganic Chemistry and Catalysis, Department of Chemistry, Utrecht University, Sorbonnelaan 16, 3584 CA Utrecht,
The Netherlands
|
| 3 |
Boreskov Institute of Catalysis, Ak. Lavrentieva 5, Novosibirsk 630090, Russia
|
| 4 |
van‘t Hoff Institute for Molecular Sciences, University of Amsterdam, PO Box 94157, 1090 GD Amsterdam, The Netherlands
|
|
Funding (2)
|
1
|
Netherlands Organisation for Scientific Research
|
047.005.03.96
|
|
2
|
Netherlands Organisation for Scientific Research
|
047.015.004
|
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 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 CuZn α-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 C, Cu0 is likely composing most of the active phase, whereas above 300 C, the sharp increase in the number Zn0-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.