Tri-coordinated boron species in confined boron oxide catalysts for enhanced low-temperature oxidative dehydrogenation of propane
Abstract
Boron-based catalysts exhibit great potential for oxidative dehydrogenation of propane (ODHP) to produce olefins. The straightforward systhesis of confined boron-based catalyst 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 angle of O−B−O and B−O−B and system disorder of BOx species increased significantly on molten state, favoring the dispersion of BOx species and formation of B−OH groups, which drove the uprush of propane conversion.
