Borosilicate zeolite enriched in defect boron sites boosting the low-temperature oxidative dehydrogenation of propane

Abstract

Borosilicate zeolites are the active catalysts in oxidative dehydrogenation of propane (ODHP), which provide an ideal platform to explore the origin of catalytic activity for boron-containing catalysts as well as the construction of highly active boron centers. Herein, we report that the incompletely crystallized MFI-type borosilicate zeolite catalyst displays extraordinary performance in ODHP, exhibiting an olefin productivity of 4.75 golefin gcat−1 h−1 under low reaction temperature (445 °C) and high weight-hour-space-velocity (WHSV, 37.6 gC3H8 gcat−1 h−1). A combination of solid-state NMR, dual-beam FTIR, and in-situ DRIFT measurements reveal that the boron species are anchored to the zeolite matrix in the form of open coordination. Meanwhile, the ample SiOH groups on the surface facilitate the formation of hydrogen bonds with the BOH in defective boron species and inhibit the excessive leaching of boron. During the ODHP process, the isolated boron species would dynamically transform into aggregated ones, being closely related to the increased catalytic activity. The BOH groups in aggregated BOx species that hydrogen bond with adjacent SiOH groups are identified as the active center and high efficiency in catalyzing ODHP reaction at low temperature.