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Chemische Prozesse und Phasenübergänge Vortrag: Fr., 11:30–11:50 F-V63
Time-resolved and operando XAS studies on heterogeneous catalysts in
liquid phase and in supercritical fluids up to 200 bar
Jan-Dierk Grunwaldt 1 , Alfons Baiker 1
1 Institute for Chemical and Bioengineering, Department of Chemistry and Applied
Biosciences, ETH Zurich, Hoenggerberg, HCI, CH-8093 Zurich
Catalyst characterization during preparation, activation and under reaction conditions
is important for a targeted catalyst development. X-ray absorption spectroscopy is a
valuable tool for this, since it is element-specific, information both on amorphous and
crystalline materials can be gained and it can be used in situ under reaction conditions.
In order to mimic the conditions of a catalyst under reaction conditions, the in situ
cell should operate as closely as possible to the reaction conditions found in a catalytic
reaction [1].
Mostly, in situ spectroscopic studies on heterogeneous catalysts are reported at normal
pressure and in gas phase. However, many heterogeneously catalysed reactions
are performed in liquids or even at elevated pressure [2]. Although the study of such
reactions is equally important, in situ studies in these areas are only seldomly reported.
The potential of XANES and/or EXAFS are discussed in these areas focusing
on Pd- and Pd-Bi-catalysed selective oxidation of alcohols to the corresponding aldehydes.
Starting with investigations in liquid phase [3], we recently succeeded in deriving
structure-performance relationships even under the demanding conditions of supercritical
fluids [4,5].
[1] J.-D. Grunwaldt, M. Caravati, S. Hannemann, A. Baiker, Phys. Chem. Chem.
Phys. 6 (2004) 3037.
[2] J. D. Grunwaldt and A. Baiker, Phys. Chem. Chem. Phys. 7 (2005) 3526.
[3] C. Keresszegi, J.-D. Grunwaldt, T. Mallat, A. Baiker, J. Catal. 222 (2004) 268
[4] J.-D. Grunwaldt, M. Caravati, M. Ramin, A. Baiker, HASYLAB Highlight Research
Report, Newsletter 08-2004.
[5] J.-D. Grunwaldt, M. Caravati, A. Baiker, J. Phys. Chem. B, in press.