Local Structure of the Zeolitic Catalytically Active Site during Reaction

• Published in: Journal of the American Chemical Society Vol. 126; no. 14; pp. 4506 - 4507
• Main Authors: van Bokhoven, Jeroen A, van der Eerden, Ad M. J, Prins, Roel
• Format: Journal Article
• Language: English
• Published: Washington, DC American Chemical Society 14-04-2004
• Subjects: Catalysis; Catalytic reactions; Chemistry; Exact sciences and technology; General and physical chemistry; Theory of reactions, general kinetics. Catalysis. Nomenclature, chemical documentation, computer chemistry; Ammonium; Catalytic reaction; Oligomerization; Hydrocarbon; Ethylene; Aluminosilicates; Modified catalyst; Experimental study; EXAFS spectrometry; Molecular sieve; Local structure; Catalytic site; Ion exchange; Catalyst activity
• ISSN: 0002-7863; 1520-5126
• DOI: 10.1021/ja031755j

The structural changes of the catalytic active site that occur during catalytic reaction in an acidic zeolite are detected. The local structure of the zeolitic Brønsted active site is a distorted tetrahedrally coordinated aluminum that has three short and one long aluminum−oxygen bond. Using in situ Al K edge X-ray absorption spectroscopy, the adsorption of a reactive intermediate in the oligomerization of ethene changed the local structure of the catalytic active site; the long aluminum oxygen bond is partially relaxed. At increasingly higher temperature, extensive coking of the catalyst frees the Brønsted acid site from the reactive intermediate, restoring the asymmetric coordination. These measurements show that application of in situ Al K edge spectroscopy provides fundamental insight into the structure of zeolitic catalytically active sites during catalytic action.