Highly Efficient Dehydrogenation of 2,3-Butanediol Induced by Metal–Support Interface over Cu-SiO₂ Catalysts

Abstract

In the present work, Cu–SiO2 catalysts were synthesized by the modified one-pot hydrothermal strategy and employed in the anaerobic dehydrogenation of 2,3-butanediol to clarify the specific dehydrogenation mechanism of diols. Characterization results testified that the properties of −Si–O–Cu–O–Si– structures (CuO-like phase) formed in Cu–SiO2 catalysts can be regulated by precisely tuning the copper loading and synthetic solution alkalinity. The superior catalytic performance with 76.0% conversion of 2,3-butanediol and 94.5% selectivity toward acetoin was achieved over the resulting 20Cu–SiO2-10.5 catalyst. Both experimental and DFT studies demonstrated that the dehydrogenation performance of Cu–SiO2 catalysts originated from the metal–support interface via the synergic catalysis of the interfacial CuO-like phase and Cu0 sites. The CuO-like phase promotes the cleavage of the −O–H bond in 2,3-butanediol by interacting with the Cu2+–O2– pair, and subsequently the other H atom is removed from the α-C–H bond in the generated alkoxy intermediate on neighboring Cu0 sites. Meanwhile, 2,3-butanediol follows the reaction pathway of the dehydrogenation of two −OH groups on the surface of Cu particles, and the generated dialkoxy intermediate strongly adsorbs on Cu0 sites, leading to the deactivation of Cu–SiO2 catalysts as well as the catalytic inertness of impregnated Cu catalysts only having Cu0 sites.

Dehydrogenation of 2,3-Butanediol to Acetoin Using Copper Catalysts

“…However, for Cu-ZrO 2 , acetoin selectivity increases because the presence of H 2 prevents acetoin from dehydrogenating to 2,3-butanedione. These results are different from Yuan et al who stated that impregnated Cu catalysts (Cu/γ-Al 2 O 3 and Cu/ZrO 2 ), synthesized by the impregnation method, were inert for 2,3-BDO dehydrogenation (0% conversion of 2,3-BDO at a reaction temperature of 280 °C). This difference can be attributed to the difference in the operating conditions where the weight hourly space velocity (WHSV) used in this work is 0.25 h –1 , while the WHSV that Yuan used was 60 h –1 .…”

“…However, for Cu-ZrO 2 , acetoin selectivity increases because the presence of H 2 prevents acetoin from dehydrogenating to 2,3-butanedione. These results are different from Yuan et al17 who stated that impregnated Cu catalysts (Cu/γ-Al 2 O 3…”

“…Also, the selectivity to acetoin was higher over Cu-ZSM-5 (23) (9.5%) than those over ZSM-5 (50) and ZSM-5 (280) with a H 2 /2,3-BDO molar ratio of 5. Yuan et al 17 investigated several w-Cu-SiO-x catalysts (where w and x denote the copper loading and pH of the synthetic solution) synthesized by the modified one-pot hydrothermal method to convert 2,3-BDO to acetoin at 280 °C. They stated that superior catalytic performance was achieved over the 20Cu-SiO-10.5 catalyst with 76.0% conversion of 2,3-BDO and 94.5% selectivity toward acetoin.…”

Surface/Lattice Oxygen Synergism of Durable CuO Catalysts for Tandem Dehydrogenation–Oxidation of Glycerol to Carboxylic Acids in Oxygen-Free Medium

“…The slab models including four atomic layers were constructed with a vacuum space of 8.0 Å and 3 × 3 × 2 Monkhorst-Pack k -point grid for surface calculations. During geometry optimizations, the atoms in the bottom two atomic layers were fixed at their bulk-truncated positions and those in top atomic layers along with the adsorbates were fully relaxed. , …”

“…During geometry optimizations, the atoms in the bottom two atomic layers were fixed at their bulk-truncated positions and those in top atomic layers along with the adsorbates were fully relaxed. 39,40 ■ RESULTS AND DISCUSSION Catalyst Screening and Benchmark Data. Despite extensive studies on the aerobic oxidation of alcohols and polyols, 13,16,19,41 the experimental data on the role of surface/ lattice oxygen in non-noble metal oxides in activating the C−H bond (dehydrogenation reaction) are still lacking in the current literature.…”