Selective hydrogenation of unsaturated carbonyls by Ni-Fe-based alloy catalysts

Ni-Fe alloy catalysts prepared by a simple hydrothermal method and subsequent H-2 treatment exhibited the greatest activity and selectivity for the hydrogenation of biomass-derived furfural to furfuryl alcohol among the examined second metals, such as Al, Ga, In, Co, and Ti. This work reveals that the alloying of Ni and Fe is a key factor in achieving highly selective hydrogenation of the C=O moiety in unsaturated carbonyl substrates. We found that decreasing the temperature of H-2 treatment (i.e. decreasing the crystallite size), e.g. Ni-Fe(2)HT-573 K (TOF = 952 h(-1)), increased the activity compared to that over Ni-Fe(2)HT-673 (TOF = 375 h(-1)) for furfural hydrogenation. This result suggests that a low-coordinated Ni-Fe alloy was imperative for the catalytic cycle. Moreover, the effect of the metal/support interface was critical; despite the high catalytic performance of Ni-Fe/TiO2, Ni-Fe/Al2O3, and Ni-Fe/CeO2, Ni-Fe supported on SiO2, taeniolite, and hydrotalcite catalysts were ineffective. Vibrational studies using FT-IR measurement confirmed that furfural was physically adsorbed on the surface of the Ni-Fe alloy catalyst via an. eta(1)(O) configuration. The synthetic scope of the Ni-Fe catalytic system was very broad; various types of unsaturated carbonyls, such as unsaturated aromatics, unconjugated aliphatics, and a large substituent, were selectively converted into the corresponding unsaturated alcohols.