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Abstract Bulk boron materials, such as hexagonal boron nitride (h‐BN), are highly selective catalysts for the oxidative dehydrogenation of propane (ODHP). Previous attempts to improve the productivity of these systems involved the immobilization of boron on silica and resulted in less selective catalysts. Here, we report that acid‐treated, activated carbon‐supported boron preparedviaincipient wetness impregnation with boric acid (B/OAC) exhibits equal propylene selectivity and improved productivity (kgpropylene kgcat−1 hr−1) as compared to h‐BN. Characterization of the fresh and spent catalysts with infrared, Raman, X‐ray photoelectron, and solid‐state NMR spectroscopies reveals the presence of oxidized/hydrolyzed boron that is clustered on the surface of the support.
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B‐MWW Zeolite: The Case Against Single‐Site Catalysis
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). Using11B solid‐state NMR spectroscopy, we show that the majority of boron species in B‐MWW exist as isolated BO3units, 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 BO3units 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.
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- PAR ID:
- 10136805
- Publisher / Repository:
- Wiley Blackwell (John Wiley & Sons)
- Date Published:
- Journal Name:
- Angewandte Chemie International Edition
- Volume:
- 59
- Issue:
- 16
- ISSN:
- 1433-7851
- Page Range / eLocation ID:
- p. 6546-6550
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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