Hydrogenative rearrangement of bioderived furfurals to cyclopentanones over Ni/Nb2O5 catalysts: Promotion effect of reducible NbOx and water

Selective aqueous hydrogenation of furfurals to valuable cyclopentanones is attractive for biomass utilization. Herein, Ni/Nb2O5 catalysts with different calcination temperatures were synthesized and employed to study the effect of reducible NbOx species and water solvent on the aqueous hydrogenation-rearrangement of furfural. A significantly higher cyclopentanone (CPO) yield (>92 %) was achieved in water on Ni/Nb2O5-500, while no CPO was detected in heptane. Catalysts characterization indicated that the calcination temperature of Nb2O5 determined the crystallinity and modulated reducible NbOx. Kinetic and isotopic experiments elucidated that the excellent catalytic performance of Ni/Nb2O5 remarkably correlated with surface reducible NbOx species and H2O-mediated effect. NbOx species closely interacted with Ni sites, in which Ni was in charge of H2 activation and NbOx facilitated furfural adsorption via flat configuration. Water helped furfural activation and active hydrogen transfer between Ni sites and adsorbed furfural on NbOx sites, thus significantly boosted aqueous hydrogenation of furfural to CPO.