Vanadium‐Catalyzed Deoxydehydration of Glycerol Without an External Reductant

Abstract

A vanadium‐catalysed deoxydehydration (DODH) of neat glycerol has been developed. Cheap and readily available ammonium metavanadate (NH4VO3) affords higher yields of allyl alcohol than the well‐established catalyst methyltrioxorhenium. A study in which deuterium‐labelled glycerol was used was undertaken to further elucidate the dual role of glycerol as both an oxidant and reductant. This study led to the proposal of a metal‐catalysed DODH mechanism for the production of allyl alcohol and a deeper understanding of the formation of the byproducts acrolein and propanal.

Gas-phase conversion of glycerol to allyl alcohol over vanadium-supported zeolite beta

“…Although the mechanism identified by J. Yi et al and A. R. Petersen et al [20,23] (which only requires the presence of the metal centre) cannot be discarded, the different behavior of the two samples (with similar vanadium content) suggests that a pathway involving just the vanadium species is not the main route for the conversion of glycerol to allyl alcohol in the present conditions. On the other hand, taking into consideration that the selectivity to acrolein tends to increase with the decrease of the acidity, it would be expected a higher selectivity towards this compound for the sample Cs/BEA/V when compared with the sample BEA/V, but we observe, instead, a reduction of the selectivity to acrolein and a significant increase of the selectivity to allyl alcohol.…”

“…was recently identified by A. R. Petersen et al [23] who conducted a liquid phase comprehensive study using NH 4 VO 3 as catalyst and deuterium-labelled glycerol, in order to elucidate the role of glycerol in the formation of allyl alcohol.…”

“…Vanadium compounds supported on zeolites have proved to be successful catalysts for the conversion of glycerol to acrylic acid [22]. To the best of our knowledge, these bifunctional catalysts have never been tested in the direct conversion of glycerol to allyl alcohol, although NH 4 VO 3 was shown to be active in liquid phase [23]. In this work, we intend to evaluate the…”

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

“…For example, as a bidentate ligand, glycerol can form either a six‐membered chelate if the two primary OH groups bind to the metal center, or a five‐membered chelate by binding through a primary and a secondary OH group. The binding mode of vicinal diols will affect the energy barrier of the condensation step, which may be lowered by invoking a water molecule in a proton relay mechanism . For a complete understanding of the mechanism, it would be essential to directly detect intermediately formed surface species (with their lifetimes matching the time scale of spectroscopic probing), determine the kinetic constants for their evolution, and relate these to the measured overall kinetics.…”

“…Deuterium‐labelled compounds can be used to rule out some competing pathways (e. g., dehydration‐hydrogenation) other than the classical DODH mechanism . For instance, 2‐[D 1 ]glycerol should afford 2‐[D 1 ]allyl alcohol without H/D scrambling, if the classical DODH mechanism is operative and the reductant is not the reactant itself; acrolein, on the other hand, is usually produced via two successive acid‐catalyzed dehydration of glycerol with the second dehydration step scrambling H and D atoms, so a mixture of 2‐[D 1 ]acrolein and non‐labeled acrolein will be formed in this scenario.…”