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Abstract:
Adsorption phenomena have been seldom studied, but play an important role in oxidation catalysis. The knowledge about heat of adsorption of reactant on the surface of a catalyst can contribute to a better understanding of the complex microkinetics. Moreover, the quantitative data provide a basis for theoretical modeling. Since perhaps only a minor fraction of all surface atoms form active centers, the determination of their number and strength requires a sensitive analytical method. Here, we focus on adsorption microcalorimetry [1]. To facilitate the correlation of microcalorimetric results with the catalytic performance, a molecule similar to the reactant, or the reactant itself, was used. Tads. was chosen lower than Treaction to separate the adsorption process from the catalytic reactions.
In this work, we will demonstrate how structure-activity correlations can be established by combining microcalorimetry with electron microscopy and spectroscopic techniques, like IR and XPS. The power of these complementary methods will be illustrated by choosing the following examples: (i) carbon-based catalysts (oCNT) for ODH of propane or ethylbenzene [2], (ii) supported metals (Pd/N-CNT) for liquid phase oxidation of benzyl alcohol [3], (iii) supported oxides (CeO2/support) for HCl oxidation [4], and (iv) mixed metal oxides (MoVTeNb oxide) for selective oxidation of propane to acrylic acid [5].
[1] S. Wrabetz, R. Schlögl, F. Jentoft et.al., J. Catal. 269 (2010) 351-358.
[2] B. Frank, S. Wrabetz, A. Trunschke, R. Schlögl, et.al., ChemPhysChem 12 (2011) 2709-2713.
[3] R. Arrigio, S. Wrabetz et.al., PCCP 14 (2012) 10523-10532.
[4] R. Farra, S. Wrabetz, D. Teschner et.al., accepted, PCCP, Dec. 2012
[5] M. Hävecker, S. Wrabetz, A. Trunschke et.al., J.of Catalysis. 285 (2012) 48-60.
