Tri-Coordinated Boron Species in Confined Boron Oxide Catalysts for Enhanced Low-Temperature Oxidative Dehydrogenation of Propane
Graphical Abstract
The confined BOx@SiO2 with highly dispersed BOx species was synthesized by the in situ transformation of BN@SiO2, which showed a remarkable activity of a unique C3H8 conversion uprush increasing from 5.3% at 410 °C to 28.4% at 424.6 °C for oxidative dehydrogenation of propane. The key for the efficient C3H8 activation was the increased amount of tri-coordinated B─OH derived from the dispersion of molten BOx species within spatially confined SiO2.
Abstract
Boron-based catalysts exhibit great potential for oxidative dehydrogenation of propane (ODHP) to produce olefins. The straightforward synthesis of confined boron-based catalysts commonly using H3BO3 is intractable because of its abundant hydroxyl groups easily interacting with the supports in a spatially nonselective manner. Herein, we managed to construct a confined BOx@SiO2 catalyst showing an impressive low-temperature (400 °C) activity. This catalyst was prepared via the encapsulation of BN nanosheets by SiO2 shell and subsequent oxidization steps. The in situ generated boron–oxygen species were anchored to silica shells via B─O─Si and hydrogen bonds. BOx@SiO2 exhibited a unique catalytic behavior of propane conversion uprush, increasing from 5.3% at 410 °C to 28.4% at 424.6 °C for ODHP reaction. That was attributed to the efficient activation of propane triggered by the newly formed tri-coordinated B─OH (B[3]a and B[3]b) active sites from the dispersion of molten BOx species in confined SiO2. Ab initio molecular dynamics (AIMD) simulations revealed that in the confined structure, the bond angles of O─B─O and B─O─B and system disorder of BOx species increased significantly in molten state, favoring the dispersion of BOx species and formation of B─OH groups, which drove the uprush of propane conversion.
Conflict of Interests
The authors declare no conflict of interest.
Open Research
Data Availability Statement
Research data are not shared.