Zeolite‐Supported Rhenium Catalysts for the Deoxydehydration of 1,2‐Hexanediol to 1‐Hexene

Abstract

For the first time ammonium perrhenate (APR) supported on zeolites of the types H-β, H-ZSM-5 and HÀ Y were shown to be efficient catalysts for the deoxydehydration (DODH). They catalyzed the transformation of 1,2-hexanediol (1,2-HDO) to 1hexene in the presence of 3-octanol as reductant and solvent with productivities up to 0.24 mol 1-hexene • g Re À 1 • h À 1 . The productivity decreased with increasing Si : Al ratio, independent of the zeolite structure. Catalyst characterization indicates Re-species to preferably bind to the Al centers of the support, resulting in a higher amount of active metal centers.

Deoxydehydration of Biomass‐Derived Polyols Over Silver‐Modified Ceria‐Supported Rhenium Catalyst with Molecular Hydrogen

“…The activity and turnover number (TON) of ReO x ‐Pd/CeO 2 were much higher than those of the homogeneous Re catalyst systems, which also supported the heterogeneous catalysis [40] . On the other hand, solid Re catalysts on other supports have been reported to have comparable activity to homogeneous catalysts, and the involvement of leached species in the catalysis cannot be excluded [33,53] . We next developed ReO x ‐Au/CeO 2 catalysts for DODH [54–57] .…”

“…Most reported DODH systems use homogeneous high‐valent Re catalysts such as CH 3 ReO 3 , ReO 4 − , and monomeric Re VII complexes [26] . The systems in earlier works employ expensive reductants such as PPh 3 , [27,28] and recently reported systems typically use less‐expensive secondary alcohols such as 3‐octanol and 2‐propanol [26,29–34] . However, even secondary alcohols have high price and low atom efficiency as reductants, and their application to the production of bulk chemicals is difficult [20] .…”

“…[26] The systems in earlier works employ expensive reductants such as PPh 3 , [27,28] and recently reported systems typically use lessexpensive secondary alcohols such as 3-octanol and 2propanol. [26,[29][30][31][32][33][34] However, even secondary alcohols have high price and low atom efficiency as reductants, and their application to the production of bulk chemicals is difficult. [20] In addition, similar reactivity of reductant and substrate and undesired side reaction of reductant-derived products (ketones) lower the selectivity of the system.…”

“…[40] On the other hand, solid Re catalysts on other supports have been reported to have comparable activity to homogeneous catalysts, and the involvement of leached species in the catalysis cannot be excluded. [33,53] We next developed ReO x -Au/CeO 2 catalysts for DODH. [54][55][56][57] The much lower activity of Au in C=C hydrogenation than Pd enables to keep the C=C bonds in the DODH products unchanged.…”

Titania-supported molybdenum oxide combined with Au nanoparticles as a hydrogen-driven deoxydehydration catalyst of diol compounds

“…However, examples of heterogeneous catalysts for DODH are limited, since the Re species can be relatively easily leached from the solid surface and the leached species may participate in the reaction. [16][17][18] The first stable heterogeneous catalyst ReO x /TiO 2 was reported by Palkovits et al 19 for the conversion of 1,2-hexanediol to 1-hexene using 3-octanol as a reductant. Later, Kon et al reported ReO x /γ-Al 2 O 3 as a leaching-free solid DODH catalyst for glycerol conversion to allyl alcohol using 2-hexanol as a reductant.…”