Furfural
and 5-hydroxymethylfurfural stand out as bridges connecting
biomass raw materials to the biorefinery industry. Their reductive
transformations by hydroconversion are key routes toward a wide variety
of chemicals and biofuels, and heterogeneous catalysis plays a central
role in these reactions. The catalyst efficiency highly depends on
the nature of metals, supports, and additives, on the catalyst preparation
procedure, and obviously on reaction conditions to which catalyst
and reactants are exposed: solvent, pressure, and temperature. The
present review focuses on the roles played by the catalyst at the
molecular level in the hydroconversion of furfural and 5-hydroxymethylfurfural
in the gas or liquid phases, including catalytic hydrogen transfer
routes and electro/photoreduction, into oxygenates or hydrocarbons
(e.g., furfuryl alcohol, 2,5-bis(hydroxymethyl)furan, cyclopentanone,
1,5-pentanediol, 2-methylfuran, 2,5-dimethylfuran, furan, furfuryl
ethers, etc.). The mechanism of adsorption of the reactant and the
mechanism of the reaction of hydroconversion are correlated to the
specificities of each active metal, both noble (Pt, Pd, Ru, Au, Rh,
and Ir) and non-noble (Ni, Cu, Co, Mo, and Fe), with an emphasis on
the role of the support and of additives on catalytic performances
(conversion, yield, and stability). The reusability of catalytic systems
(deactivation mechanism, protection, and regeneration methods) is
also discussed.
