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J. Phys. Chem. B 2004, 108, 4116-4126
Generation and Characterization of Well-Defined Zn2+ Lewis Acid Sites in Ion Exchanged Zeolite BEA Jochen Penzien,† Anuji Abraham,‡ Jeroen A. van Bokhoven,‡ Andreas Jentys,† Thomas E. Mu1 ller,† Carsten Sievers,† and Johannes A. Lercher*,† Lehrstuhl fu¨r Technische Chemie II, Technische UniVersita¨t Mu¨nchen, Lichtenbergstrasse 4, 85747 Garching, Germany, and Federal Institute of Technology (ETH), 8093-CH Zu¨rich, Switzerland ReceiVed: October 31, 2003; In Final Form: January 19, 2004
Bifunctional, Lewis, and Brønsted acidic molecular sieves were prepared by stepwise zinc ion exchange of zeolite BEA. The relation between the location of the Zn2+ cations in the zeolite structure and the Lewis acidity of the metal cations was explored. Several techniques were used for the detailed characterization of the material, including IR spectroscopy, with pyridine and acetonitrile as probe molecules, temperature programmed desorption, with ammonia and 2-propylamine as probe molecules, X-ray absorption spectroscopy, and 27Al MAS and MQMAS NMR spectroscopy. At low zinc concentrations (
