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

Published

November 6, 2023

Author(s)

Melissa Cendejas, Oscar Paredes Mellone, Unni Kurumbail, Zisheng Zhang, Jacob Jansen, Faysal Ibrahim, Son Dong, John Vinson, Anastassia Alexandrova, Dimosthenis Sokaras, Simon Bare, Ive Hermans

Abstract

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 combi-nation of surface mediated and gas phase propagated radical reactions with the relative importance of both depend-ing on the surface-to-void-volume ratio. Here we demonstrate the unique capability of operando X-ray Raman spec-troscopy (XRS) to investigate the oxyfunctionalization of the catalyst under reaction conditions (1 mm outer diameter reactor, 500 °C 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 reac-tion rate when the surface reaction dominates and an enhanced reaction rate when the gas phase contribution domi-nates. 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.

Citation

Journal of the American Chemical Society

Pub Type

Journals

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https://doi.org/10.1021/jacs.3c08679

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Citation

Cendejas, M. , Paredes Mellone, O. , Kurumbail, U. , Zhang, Z. , Jansen, J. , Ibrahim, F. , Dong, S. , Vinson, J. , Alexandrova, A. , Sokaras, D. , Bare, S. and Hermans, I. (2023), Tracking Active Phase Behavior on Boron Nitride during the Oxidative Dehydrogenation of Propane Using Operando X-Ray Raman Spectroscopy, Journal of the American Chemical Society, [online], https://doi.org/10.1021/jacs.3c08679, https://tsapps.nist.gov/publication/get_pdf.cfm?pub_id=956373 (Accessed April 27, 2024)