Catalyst Characterization by XAS and XES Spectroscopies: In Situ and Operando Experiments
The role of a catalyst in improving the activity and the selectivity of a given chemical reaction is provided, together with a discussion on the reasons why XAS and XES are so important techniques in the understanding, at the molecular level, of the struc
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Catalyst Characterization by XAS and XES Spectroscopies: In Situ and Operando Experiments Francesca Bonino, Elena Groppo, Carmelo Prestipino, Giovanni Agostini, Andrea Piovano, Diego Gianolio, Lorenzo Mino, Erik Gallo and Carlo Lamberti
Abstract The role of a catalyst in improving the activity and the selectivity of a given chemical reaction is provided, together with a discussion on the reasons why XAS and XES are so important techniques in the understanding, at the molecular level, of the structure and of the electronic configuration of a working catalyst. Two industrially relevant catalysts are described as key studies: (i) the combined XAS/XES in situ study on TS-1 catalyst provided the structure of the Ti active center in selective oxidation with H2 O2 , and its evolution upon molecular coordination; (ii) the combined in situ/operando XAS study revealed the red-ox catalytic cycle of CuCl2 /Al2 O3 during the ethylene oxychlorination reaction.
F. Bonino · E. Groppo · G. Agostini · L. Mino Department of Chemistry, NIS Centre of Excellence and INSTM Reference Center, University of Turin, Via Giuria 7, 10125 Torino, Italy C. Lamberti (B) Department of Chemistry, CrisDi Interedepartmental Centre for Crystallography and INSTM Reference Center, University of Turin, Via Giuria 7, 10125 Torino, Italy e-mail: [email protected] C. Lamberti Southern Federal University, Zorge Street 5, 344090 Rostov-on-Don, Russia C. Prestipino Institut des Sciences Chimiques de Rennes, Université de Rennes 1, UMR CNRS-UR1 6226, Campus de Beaulieu, Bât 10B, 35042 Rennes Cedex, France A. Piovano Institut Laue-Langevin (ILL), BP 156 X, 38042 Grenoble Cedex, France D. Gianolio Diamond Light Source Ltd, Harwell Science and Innovation Campus, Didcot OX11 0DE, UK G. Agostini · E. Gallo European Synchrotron Radiation Facility (ESRF), 6 Rue Jules Horowitz, 38043 Grenoble, France
S. Mobilio et al. (eds.), Synchrotron Radiation, DOI: 10.1007/978-3-642-55315-8_28, © Springer-Verlag Berlin Heidelberg 2015
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Fig. 28.1 Part a Schematic representation of a catalyzed (dotted curve) and un-catalyzed (solid line) path of the general chemical reaction A + B ↔ (A · · · B)‡ ↔ C. The catalyst allows to lower the activation energy from E to E cat . Part b Example of a possible catalytic cycle for the reaction reported in a. Part c ideal example of catalyzed increased selectivity towards C
28.1 Introduction This chapter provides a brief description of the basic concepts of catalysis and discusses the role of XAS and XES to elucidate the catalytic activity. The understanding of the structural (EXAFS) and electronic (XANES and XES) properties of the catalytic active site is of prime significance to obtain a rational catalyst design that points towards the improvement of already established reaction and to develop catalyst for new reactions. Consider a given chemical reactions, where reactants A and B yield the product C. In the simplified scheme reported in Fig. 28.1a, the reaction proceeds through an intermediate state (A · ·
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