Probing the Transformation of Boron Nitride Catalysts under Oxidative Dehydrogenation Conditions

Love, Alyssa
Thomas, Brijith
Specht, Sarah
Hanrahan, Michael
Venegas, Juan
Burt, Samuel
Grant, Joseph
Cendejas, Melissa
McDermott, William
Rossini, Aaron
Hermans, Ive
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Hexagonal boron nitride (h-BN) and boron nitride nanotubes (BNNTs) were recently reported as highly selective catalysts for the oxidative dehydrogenation (ODH) of alkanes to olefins in the gas phase. Previous studies revealed a substantial increase in surface oxygen content after exposure to ODH conditions (heating to ca. 500 °C under a flow of alkane and oxygen); however, the complexity of these materials has thus far precluded an in-depth understanding of the oxygenated surface species. In this contribution, we combine advanced NMR spectroscopy experiments with scanning electron microscopy (SEM) and soft X-ray absorption spectroscopy (XAS) to characterize the molecular structure of the oxygen functionalized phase that arises on h-BN and BNNTs following catalytic testing for ODH of propane. The pristine BN materials are readily oxidized and hydrolyzed under ODH reaction conditions to yield a phase consisting of three coordinate boron sites with variable numbers of hydroxyl and bridging oxide groups which is denoted B(OH)xO3-x (where x = 0-3). Evidence for this robust oxide phase revises previous literature hypotheses of hydroxylated BN edges as the active component on h-BN.

<p>This document is the Accepted Manuscript version of a Published Work that appeared in final form in <em>Journal of the American Chemical Society</em>, copyright © American Chemical Society after peer review and technical editing by the publisher. To access the final edited and published work see DOI: <a href="" target="_blank">10.1021/jacs.8b08165</a>. Posted with permission.</p>