TY - JOUR
T1 - B-MWW Zeolite
T2 - The Case Against Single-Site Catalysis
AU - Altvater, Natalie R.
AU - Dorn, Rick W.
AU - Cendejas, Melissa C.
AU - McDermott, William P.
AU - Thomas, Brijith
AU - Rossini, Aaron J.
AU - Hermans, Ive
N1 - Publisher Copyright:
© 2020 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
PY - 2020/4/16
Y1 - 2020/4/16
N2 - 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). Using 11B solid-state NMR spectroscopy, we show that the majority of boron species in B-MWW exist as isolated BO3 units, 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 BO3 units 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.
AB - 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). Using 11B solid-state NMR spectroscopy, we show that the majority of boron species in B-MWW exist as isolated BO3 units, 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 BO3 units 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.
KW - boron
KW - heterogeneous catalysis
KW - oxidative dehydrogenation
KW - solid-state NMR
KW - zeolites
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U2 - 10.1002/anie.201914696
DO - 10.1002/anie.201914696
M3 - Article
C2 - 32026560
AN - SCOPUS:85080147929
SN - 1433-7851
VL - 59
SP - 6546
EP - 6550
JO - Angewandte Chemie - International Edition
JF - Angewandte Chemie - International Edition
IS - 16
ER -