A Highly Selective Metal‐Free Boron‐Based Catalyst for Oxidative Dehydrogenation of Ethylbenzene

Abstract

Main observation and conclusion Oxidative dehydrogenation of ethylbenzene is considered as an alternative route to styrene because of its exothermic and irreversible reaction nature, but encounters low styrene selectivity due to the deep‐oxidation over metal oxide‐based catalysts. Herein, we reported that a metal‐free boron‐based catalyst consisting of boron phosphate and boron nitride (BPO4/BN) exhibited high activity and selectivity in oxidative dehydrogenation of ethylbenzene to styrene. High selectivity of styrene (95.1%) was achieved at 27.7% ethylbenzene conversion level over the optimized BPO4/BN catalyst. The tetra‐coordinated boron (BO4) species of BPO4 was speculated to be responsible for the ODH of ethylbenzene, and a synergistic effect between BPO4 and BN can remarkably improve the catalytic performance of the BPO4/BN catalyst. The optimized BPO4/BN catalyst showed a higher styrene formation rate of 4.0 mmol gcat−1·h−1, compared individually to BPO4 (2.8 mmol·gcat–1·h–1) and BN (0.5 mmol·gcat–1·h–1).

Low-Temperature C–H Bond Activation: Ethylbenzene-to-Styrene Conversion on Rutile TiO2(110)

“…Unlike the direct dehydrogenation process, oxidative dehydrogenation is exothermic and thermodynamically favorable and can be performed at a lower temperature . With extensive studies, a series of catalysts have been developed for the efficient oxidative dehydrogenation of EB, including conventional metal-based catalysts (e.g., cerium oxides, vanadium oxides, , and metal phosphates) and carbon-based catalysts (such as activated carbon, carbon nanotubes, and so on). − However, the temperature of EB oxidative dehydrogenation to styrene in these studies is still >350 °C. In addition, byproduct channels are difficult to control.…”

Low-Temperature C–H Bond Activation via Photocatalysis: Highly Efficient Ethylbenzene Dehydrogenation into Styrene on Rutile TiO2(110)

“…As a common olefin, styrene (C 6 H 5 CHCH 2 , ST) is an important monomer for the synthesis of high polymers, such as polystyrene and styrene–acrylonitrile. − Industrially, C 6 H 5 CHCH 2 is produced via the direct dehydrogenation (DDH) of ethylbenzene (C 6 H 5 C 2 H 5 , EB) steam over iron oxide-based catalysts at 550–650 °C. ,− Although the oxidative dehydrogenation (ODH) process can bring the reaction temperature down to 400–500 °C, it usually causes excessive oxidation of the product under high oxygen concentration, leading to an unsatisfactory selectivity and even an explosion. − Recently, although some novel catalysts (such as carbonaceous materials, boron-based catalysts and so on) obtained satisfactory C 6 H 5 CHCH 2 selectivity and C 6 H 5 C 2 H 5 conversion, the reaction temperature still exceeds 350 °C. − Thus, the dehydrogenation of C 6 H 5 C 2 H 5 into C 6 H 5 CHCH 2 with a high selectivity and conversion efficiency under mild conditions is still a huge challenge nowadays.…”

Oxidative Dehydrogenation of Propane on Boron Phosphate: A Computational Mechanistic Study

“…In BPO 4 crystal, the boron element exists in tetra-coordinated form (BO 4 ), which is electron-rich in its surrounding and thus has properties different from those of the tri-coordinated boron in B 2 O 3 and h-BN. The presence of BOH functional groups on the surface of BPO 4 has been identified. , The signal of surface tetra-coordinated boron species was also observed in the study of the ODHP process catalyzed by boron phosphate . In addition, in the study of oxidative dehydrogenation of ethylbenzene catalyzed by BPO 4 , the surface tetra-coordinated boron species was proposed to be the possible active site .…”

“…27 In addition, in the study of oxidative dehydrogenation of ethylbenzene catalyzed by BPO 4 , the surface tetracoordinated boron species was proposed to be the possible active site. 33 Thus, concerning the rich distribution of �BOH sites on the surface, it deserves to investigate their roles in the ODHP reaction.…”