The type and location of Fe cations in zeolite BEA and their structural changes under NH3-SCR conditions are reported, as they are important catalysts for the selective catalytic reduction of NOx with NH3. Adsorption of basic probe molecules such as NH3 and pyridine shows that additional Bronsted acid sites are formed at the expense of Lewis acidic octahedrally coordinated Fe cations during the aging cycle. The formation of new tetrahedrally coordinated Fe suggests that Fe cations are incorporated into the zeolite framework at tetrahedral positions. UV/vis, XAFS, and IR spectra indicate that these species, however, exist only when the samples are cooled to room temperature under NH3-SCR conditions. In situ EXAFS shows Fe cations forming bridging Fe-O-Fe species at cation exchange sites above 573 K under reaction conditions. This indicates that the Fe cations undergo a unique reversible transformation during temperature cycles under NH3-SCR conditions.     «

The type and location of Fe cations in zeolite BEA and their structural changes under NH3-SCR conditions are reported, as they are important catalysts for the selective catalytic reduction of NOx with NH3. Adsorption of basic probe molecules such as NH3 and pyridine shows that additional Bronsted acid sites are formed at the expense of Lewis acidic octahedrally coordinated Fe cations during the aging cycle. The formation of new tetrahedrally coordinated Fe suggests that Fe cations are incorporat...     »

ISI Document Delivery No.: 905ZW Times Cited: 3 Cited Reference Count: 52 Maier, Sarah M. Jentys, Andreas Janousch, Markus van Bokhoven, Jeroen A. Lercher, Johannes A. Jentys, Andreas/D-4622-2009; Janousch, Markus/B-3285-2010 Jentys, Andreas/0000-0001-5877-5042; Bayerisches Staatsministerium fur Wissenschaft, Forschung und Kuns Portions of this research were carried out at the light source facility DORIS III at DESY, Hamburg, Germany. DESY is a member of the Helmholtz Association (HGF). We would like to thank Adam Webb and Michael Murphy for assistance in using beamline X1. The Al XANES measurements were performed at the Swiss Light Source, Paul Scherrer Institute, Villigen, Switzerland, Dr. M. Janousch is gratefully acknowledged for his contribution to the measurements. We would like to thank Martin Neukamm for AAS measurements and Edith Ball for preparation of the FeBEA samples. Discussions in the framework of ERIC are gratefully acknowledged. The project was funded by the Bayerisches Staatsministerium fur Wissenschaft, Forschung und Kunst. 3 Amer chemical soc Washington     «

ISI Document Delivery No.: 905ZW Times Cited: 3 Cited Reference Count: 52 Maier, Sarah M. Jentys, Andreas Janousch, Markus van Bokhoven, Jeroen A. Lercher, Johannes A. Jentys, Andreas/D-4622-2009; Janousch, Markus/B-3285-2010 Jentys, Andreas/0000-0001-5877-5042; Bayerisches Staatsministerium fur Wissenschaft, Forschung und Kuns Portions of this research were carried out at the light source facility DORIS III at DESY, Hamburg, Germany. DESY is a member of the Helmholtz Association (HGF). We wou...     »