Selective Hydrodeoxygenation of Lignin-Derived Phenols to Aromatics Catalyzed by Nb₂O₅-Supported Iridium

Abstract

The dominating catalytic approach to aromatic hydrocarbons from renewables, deoxygenation of phenol-rich depolymerized lignin bio-oils, is hard to achieve: hydrodeoxygenation (HDO) of phenols typically leads to the loss of aromaticity and to non-negligible fractions of cyclohexanones and cyclohexanols. Here, we report a catalyst, niobia-supported iridium nanoparticles (Ir@Nb 2 O 5 ), which combines full conversion in the HDO of lignin-derived phenols with appreciable and tunable selectivity for aromatics (25–95%) under mild conditions (200–300 °C, 2.5–10 bar of H 2 ). A simple approach to the removal of Brønsted-acidic sites via Hünig’s base prevents coking and allows reaction conditions ( T > 225 °C, 2.5 bar of H 2 ), promoting high yields of aromatic hydrocarbons.

A guide to lignin valorization in biorefineries: traditional, recent, and forthcoming approaches to convert raw lignocellulose into valuable materials and chemicals

“…267,268 From this point of view, both chemocatalytic and biological pathways have been developed for the defunctionalization of lignin monomers. 267,405,[418][419][420][421] Among the possible routes for chemocatalytic upgrading of phenolic monomers, their defunctionalization through HDO reactions is particularly attractive for decreasing the complexity of the mixture of monomeric products, as well as the oxygen content of the produced molecules. 267,405,422,423 Depending on the applied process conditions, HDO of phenolic monomers can yield alkanes, aromatic hydrocarbons, phenols, or cyclohexanols (Fig.…”

“…267,268 From this point of view, both chemocatalytic and biological pathways have been developed for the defunctionalization of lignin monomers. 267,405,418–421…”

Furfural Hydrogenation Over Reduced Pure (LaBO3) and Substituted (LaB0.5B'0.5O3) (B, B': Fe, Co, Ni) Perovskites

“…They found that the selectivity is governed by metal and acid sites, catalyst amount, hydrogen pressure, and temperature. Heterogeneous metal catalysts are commonly synthesized by co‐precipitation, wet‐impregnation, precipitation‐impregnation, sol‐gel, among other methods [22–24] . However, this process has significant drawback, due to the size and shape of metal particles is difficult to control and tend to form agglomerates of metal particles, leading to a loss of active phase.…”

Hydrodeoxygenation Performance of Lignin-Derived Phenolics to Cycloalkanes: Insights into the Crystal Structures of the Nb2O5 Support

“…Therefore, Nb 2 O 5 can be used as an efficient catalytic deoxygenation support . However, its deoxygenation efficiency is also related to some key factors such as oxygen vacancy content, acidity, structural properties, interaction with active metals, etc.…”

“…26 Therefore, Nb 2 O 5 can be used as an efficient catalytic deoxygenation support. 27 However, its deoxygenation efficiency is also related to some key factors such as oxygen vacancy content, acidity, structural properties, interaction with active metals, etc. The crystal structure of Nb 2 O 5 has a great impact on the above properties; thus, it is necessary to conduct in-depth research on the catalytic effect of Nb 2 O 5 crystal structures.…”