Deoxydehydration with Molecular Hydrogen over Ceria-Supported Rhenium Catalyst with Gold Promoter

Abstract

Gold nanoparticle cocatalyst and ceria support catalyst enabled the use of H2 as a reductant for Re-catalyzed deoxydehydration (DODH), converting vicinal diols to olefins with higher activity than homogeneous Re catalysts using non-H2 reductants and with comparable selectivity. The suitable particle size (∼10 nm) of Au in ReO x -Au/CeO2 catalyst was especially effective for activating H2 while retaining the CC bond in DODH products. Glycerol was converted to allyl alcohol in 91% yield, and the TON per Re atom reached 300. This system is applicable to other substrates such as erythritol (81% yield of 1,3-butadiene).

Vanadium‐Catalyzed Deoxydehydration of Glycerol Without an External Reductant

“…The first example of the use of metal‐catalysed DODH for the conversion of glycerol to allyl alcohol was reported by Cook and Andrews . Subsequently, this reaction has been investigated by several groups using a variety of catalysts and reductants . Allyl alcohol is formed by the extrusion of the alkene from a metal diolate (Scheme C).…”

“…In a subsequent study, hydrogenation was curtailed by replacing Pd with Au. Hence the heterogeneous catalyst ReO x ‐Au/CeO 2 converted glycerol to allyl alcohol in 91 % yield with a turnover number (TON) of 300 …”

Valorization of Biomass‐derived Small Oxygenates: Kinetics, Mechanisms and Site Requirements of H2‐involved Hydrogenation and Deoxygenation Pathways over Heterogeneous Catalysts

“…The high selectivity offered by DODH pathways, simultaneously removing vicinal oxygens and forming C=C bond(s), is what makes it really attractive. Compared to many multi‐step or tandem processes all suffer from the possible ramification of forming a mixture of products (e. g., deoxygenation to both 1,2‐ and 1,3‐propanediol) and from the risks of either excessive dehydration to acrolein or excessive deoxygenation/hydrogenation to propanols, the DODH of glycerol can yield the desired allyl alcohol in a highly selective manner, with limited parallel formation of other products, as long as oversaturation (of products) or over‐reduction (of metal centers) does not occur in the presence of sufficiently potent reductants (e. g., H 2 ) …”

“…Selective production of unsaturated targets is also usually difficult to achieve in the presence of hydrogenation functions. Regardless, Tomishige and coworkers have published a series of works on CeO 2 ‐supported ReO x ‐ M ( M =Pd, Au) as relatively stable and highly efficient catalyst formulations for DODH of diols and polyols as well as sugars and sugar derivatives …”

“…With Au‐promoted ReO x /CeO 2 , for example, DODH of glycerol in H 2 produced allyl alcohol at >90 % selectivity at a comparable activity to other noble‐metal‐added catalysts, all of which produced 1‐propanol as the main product. Au, especially when present as small nanoparticles and in contact with reducible oxides, does catalyze hydrogenation and bond isomerization of allyl alcohol, albeit much less preeminently than other noble metals; however, it is still able to preserve the high selectivity (∼95 %) to the desired ally alcohol at relatively high conversions (∼60 %) . This is partly because consecutive reactions of unsaturated targets are suppressed to some extent in the presence of the diol/polyol substrate, thanks to the competitive adsorption and parallel consumption of active hydrogen species by reactant and product .…”