Tracking Active Phase Behavior on Boron Nitride during the Oxidative Dehydrogenation of Propane Using Operando X-ray Raman Spectroscopy

Hexagonal boron nitride (hBN) is a highly selective catalyst for the oxidative dehydrogenation of propane (ODHP) to propylene. Using a variety of ex situ characterization techniques, the activity of the catalyst has been attributed to the formation of an amorphous boron oxyhydroxide surface layer. T...

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Bibliographic Details
Published in:Journal of the American Chemical Society 2023-11, Vol.145 (47), p.25686-25694
Main Authors: Cendejas, Melissa C., Paredes Mellone, Oscar A., Kurumbail, Unni, Zhang, Zisheng, Jansen, Jacob H., Ibrahim, Faysal, Dong, Son, Vinson, John, Alexandrova, Anastassia N., Sokaras, Dimosthenis, Bare, Simon R., Hermans, Ive
Format: Article
Language:English
Subjects:
boron
catalysts
chemical structure
energy
INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY
oxides
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Summary:Hexagonal boron nitride (hBN) is a highly selective catalyst for the oxidative dehydrogenation of propane (ODHP) to propylene. Using a variety of ex situ characterization techniques, the activity of the catalyst has been attributed to the formation of an amorphous boron oxyhydroxide surface layer. The ODHP reaction mechanism proceeds via a combination of surface mediated and gas phase propagated radical reactions with the relative importance of both depending on the surface-to-void-volume ratio. Here we demonstrate the unique capability of operando X-ray Raman spectroscopy (XRS) to investigate the oxyfunctionalization of the catalyst under reaction conditions (1 mm outer diameter reactor, 500 to 550 °C, P = 30 kPa C3H8, 15 kPa O2, 56 kPa He). We probe the effect of a water cofeed on the surface of the activated catalyst and find that water removes boron oxyhydroxide from the surface, resulting in a lower reaction rate when the surface reaction dominates and an enhanced reaction rate when the gas phase contribution dominates. Computational description of the surface transformations at an atomic-level combined with high precision XRS spectra simulations with the OCEAN code rationalize the experimental observations. This work establishes XRS as a powerful technique for the investigation of light element-containing catalysts under working conditions.
ISSN:0002-7863
1520-5126
DOI:10.1021/jacs.3c08679