Cu-exchanged zeolites are promising materials for the selective conversion of methane to methanol. Their activity is attributed to the presence of small Cu-oxo and Cu-hydroxy clusters, but the nature of...

We present the controlled grafting synthesis of pinacolborane on amorphous silica. 11B solid-state NMR and IR spectroscopies reveal that the precursor molecule anchors monopodally to the surface and can form hydrogen-bonding interactions with neighboring unreacted silanol groups. The extent of hydrogen bonding can be controlled by the silica pretreatment dehydration temperature. Thermal treatment of the grafted boron materials under vacuum generates clusters of oxidized/hydrolyzed boron regardless of boron weight loading, illustrating that boron is highly mobile on the silica surface at elevated temperatures. The materials exhibit propane oxidative dehydrogenation activity expected for silica-supported boron catalysts. Interestingly, the kinetic behavior of these supported catalysts deviates from that of previously reported bulk boron materials, prompting further studies into the reaction kinetics over these materials. The synthetic and catalytic insights gained here can inform future studies of improved synthesis routes and reaction kinetics.

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 prepared via incipient 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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We have investigated the synthesis of hexane-1,2,5,6-tetrol (hereafter “tetrol”) from aqueous solutions of biomass-derived levoglucosanol (hereafter “Lgol”) using a (10 wt %)­Pt-(10 wt %)­WO x /TiO2 catalyst in both batch and continuous flow reactors. The tetrol selectivity was over 90% with Lgol feed concentrations of 10–30 wt %. Most of the Lgol feed stereochemistry was preserved (notably 91%), with threo-Lgol (hereafter “t-Lgol”) and erythro-Lgol (hereafter “e-Lgol”) converting to (S,S)-tetrol and (S,R)-tetrol, respectively. The rate of Lgol conversion was found to be first-order in the Lgol concentration, suggesting that the catalyst surface is not saturated with Lgol. The measured reaction order for H2 was zero, which is consistent with either a mechanism involving acid-catalyzed irreversible C–O bond cleavage of Lgol followed by metal-catalyzed hydrogenation of reactive intermediates or one where all of the metal sites are saturated with H2. When the reaction was run in a continuous flow reactor, the catalyst exhibited deactivation with increasing time-on-stream but was found partially regenerable with a consecutive calcination and reduction treatment. Deactivation was concluded to be caused mainly by carbon deposition, with some W-leaching from the catalyst in the initial stages of reaction. The here demonstrated understanding of reaction kinetics and catalyst stability could facilitate the development of improved processes to produce hexane-1,2,5,6-tetrol from biomass.