Rhenium in Heterogeneous Catalysis: A Rising Star for Hydrogenation Reactions

Bimetallic catalysts of the promoted transition metal catalysts have demonstrated excellent activity and selectivity for the hydrogenation of the range of biomass-derived oxygenates to targeted deoxygenated products. The formation of well-dispersed bimetallic interfaces in the form of either low-valent rhenium coordinated to the first metals (e.g., Pt-ReOx) or alloy nanoparticles (e.g., NiRe) is key to boost the hydrogenation activity for the carboxylic acids and phenols, respectively, and the synthesis method affects the formation of these active sites. Herein, the two representative Re-based bimetallic catalysts, i.e., Pt-ReOx/TiO2 and NiRe/SiO2, for biomass hydrogenation were synthesized through controlled surface reaction (CSR), and its efficacy toward the formation of bimetallic interfacial sites compared to the traditional synthesis method, i.e., incipient wet impregnation (IWI), was demonstrated. For the CSR, the first metal was impregnated into the supporting materials and then reduced under hydrogen flow. Subsequently, Re was selectively deposited onto the reduced metal surface by the reaction of metal hydride with NH4ReO4, denoted as ex situ CSR sample. The reduction of the first metal and rhenium deposition were also performed simultaneously under hydrogen flow, denoted as an in situ sample. The synthesized catalysts were analyzed using X-ray diffraction (XRD), H2-TPR, CO chemisorption, X-ray photoelectron spectroscopy (XPS), X-ray absorption near-edge structure (XANES), extended X-ray absorption fine structure (EXAFS), and high-resolution transmission electron microscopy (HR-TEM). The catalytic properties were probed using the selective hydrogenation of acetic acid to ethanol for Pt-ReOx/TiO2 and that of 2-methoxyphenol to cyclohexane for NiRe/SiO2. We found that the in situ CSR leads to more intimate contact of two metals, allowing for the formation of the desired Pt-ReOx and NiRe interfacial sites and thereby resulting in enhanced hydrogenation activity compared to the IWI method.

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Aqueous Phase Hydrogenation of 4-(2-Furyl)-3-buten-2-one over Different Re Phases

Díaz,

Araya-López,

Dongil

et al. 2024

Molecules

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4-(2-furyl)-3-buten-2-one (FAc) is obtained by aldol condensation of furfural and acetone and has been used in hydrodeoxygenation reactions to obtain fuel products using noble metal catalysts. The hydrogenation of FAc in the aqueous phase using metallic- and Re oxide-supported catalysts on graphite was studied, within a temperature range of 200–240 °C, in a batch reactor over a 6 h reaction period. The catalysts were characterized using N2 adsorption–desorption, TPR-H2, TPD-NH3, XRD, and XPS analyses. Catalytic reactions revealed that metallic rhenium and rhenium oxide-supported catalysts are active for the hydrogenation and Piancatelli rearrangement of FAc. Notably, metallic rhenium exhibited a fourfold higher initial rate than rhenium oxide, which was attributed to the higher dispersion of Re in the Re/G catalyst over graphite. Re/G and ReOx/G catalysts tended to rearrange and hydrogenate FAc to 2-(2-oxopropyl)cyclopenta-1-one in water.

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Rhenium in Heterogeneous Catalysis: A Rising Star for Hydrogenation Reactions

Cited by 3 publications

References 100 publications

Organic Synthesis Catalyzed by Metal Nanoparticles

Organic Synthesis Catalyzed by Metal Nanoparticles

Controlled Synthesis of PtRe and NiRe Bimetallic Catalysts for Enhanced Biomass Hydrogenation

Aqueous Phase Hydrogenation of 4-(2-Furyl)-3-buten-2-one over Different Re Phases

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