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B-MWW Zeolite: The Case Against Single-Site Catalysis |
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| Authors: | Natalie R Altvater Rick W Dorn Melissa C Cendejas William P McDermott Dr Brijith Thomas Prof?Dr Aaron J Rossini Prof?Dr Ive Hermans |
| Institution: | 1. Department of Chemical and Biological Engineering, University of Madison – Wisconsin, 1415 Engineering Drive, Madison, WI, 53706 USA
These authors contributed equally to this work.;2. Department of Chemistry, Iowa State University, 2438 Pammel Dr., Ames, IA, 50011 USA U.S. Department of Energy, Ames Laboratory, 311 Iowa State University, Ames, IA, 50011 USA These authors contributed equally to this work.;3. Department of Chemistry, University of Wisconsin – Madison, 1101 University Avenue, Madison, WI, 53706 USA These authors contributed equally to this work.;4. Department of Chemistry, University of Wisconsin – Madison, 1101 University Avenue, Madison, WI, 53706 USA;5. Department of Chemistry, Iowa State University, 2438 Pammel Dr., Ames, IA, 50011 USA;6. Department of Chemical and Biological Engineering, University of Madison – Wisconsin, 1415 Engineering Drive, Madison, WI, 53706 USA |
| Abstract: | Boron-containing materials have recently been identified as highly selective catalysts for the oxidative dehydrogenation (ODH) of alkanes to olefins. It has previously been demonstrated by several spectroscopic characterization techniques that the surface of these boron-containing ODH catalysts oxidize and hydrolyze under reaction conditions, forming an amorphous B2(OH)xO(3?x/2) (x=0–6) layer. Yet, the precise nature of the active site(s) remains elusive. In this Communication, we provide a detailed characterization of zeolite MCM-22 isomorphously substituted with boron (B-MWW). Using 11B solid-state NMR spectroscopy, we show that the majority of boron species in B-MWW exist as isolated BO3 units, fully incorporated into the zeolite framework. However, this material shows no catalytic activity for ODH of propane to propene. The catalytic inactivity of B-MWW for ODH of propane falsifies the hypothesis that site-isolated BO3 units are the active site in boron-based catalysts. This observation is at odds with other traditionally studied catalysts like vanadium-based catalysts and provides an important piece of the mechanistic puzzle. |
| Keywords: | Bor Heterogene Katalyse Oxidative Dehydrierung Festkörper-NMR Zeolithe |