Rationalizing kinetic behaviors of isolated boron sites catalyzed oxidative dehydrogenation of propane

• Published in: Nature communications Vol. 14; no. 1; p. 6520
• Main Authors: Tian, Hao, Li, Wenying, He, Linhai, Zhong, Yunzhu, Xu, Shutao, Xiao, Hai, Xu, Bingjun
• Format: Journal Article
• Language: English
• Published: London Nature Publishing Group UK 16-10-2023; Nature Publishing Group; Nature Portfolio
• Subjects: 147/135; 639/166/898; 639/638/77/887; Boron; Catalysis; Catalysts; Dehydrogenation; Enthalpy; Entropy of activation; Humanities and Social Sciences; Hydrogen bonding; Hydroxylation; Kinetics; Mathematical analysis; multidisciplinary; Propane; Reaction kinetics; Science; Science (multidisciplinary); Zeolites
• ISSN: 2041-1723; 2041-1723
• DOI: 10.1038/s41467-023-42403-2

Boron-based catalysts exhibit high alkene selectivity in oxidative dehydrogenation of propane (ODHP) but the mechanistic understanding remains incomplete. In this work, we show that the hydroxylation of framework boron species via steaming not only enhances the ODHP rate on both B-MFI and B-BEA, but also impacts the kinetics of the reaction. The altered activity, propane reaction order and the activation energy could be attributed to the hydrolysis of framework [B(OSi≡)
3
] unit to [B(OSi≡)
3−
x
(OH···O(H)Si≡)
x
] (
x
 = 1, 2, “···” represents hydrogen bonding). DFT calculations confirm that hydroxylated framework boron sites could stabilize radical species, e.g., hydroperoxyl radical, further facilitating the gas-phase radical mechanism. Variations in the contributions from gas-phase radical mechanisms in ODHP lead to the linear correlation between activation enthalpy and entropy on borosilicate zeolites. Insights gained in this work offer a general mechanistic framework to rationalize the kinetic behavior of the ODHP on boron-based catalysts.
The kinetic parameters in heterogeneous catalysis are informative in a mechanistic study. Here, the authors show the correlation between the coordination environment of isolated boron sites and the kinetics of oxidative dehydrogenation of propane.