Performant Au hydrogenation catalyst cooperated with Cu-doped Al₂O₃ for selective conversion of furfural to furfuryl alcohol at ambient pressure

Catalytic hydrogenation of furfural to furfuryl alcohol is an important upgrading process for valorization of biomass-derived furanyl platform molecules. However, selective hydrogenation of α,β-unsaturated aldehydes like furfural to the corresponding alcohols at ambient pressure remains challenging in sustainable chemistry. Till date heterogeneous Au hydrogenation catalyst has been scarcely reported for this reaction due to the low reactivity of Au for H₂ dissociation. In this work, we showed that Au nanoparticles (loading: 0.2 wt%) with a mean size of about 3 nm supported on Cu-doped Al₂O₃ can efficiently hydrogenate furfural to furfuryl alcohol in liquid phase at ambient pressure. We demonstrated that doping a small amount of Cu (2 mol%) to γ-Al₂O₃ may modify the Lewis acidity-basicity of Al₂O₃ and simultaneously induce the presence of sufficient Cu⁺ species on surface, which facilitated the hydrogen transfer from i-PrOH to furfural. Moreover, we observed an enhanced reactivity of Au toward molecular H₂ via cooperation with the Lewis acidic-basic Cu₂O-Al₂O₃ support. Hence, 100% yield to furfuryl alcohol with a productivity of 0.98 g_FA·h^-1·${\rm{g}}_{{\rm{cat}}}^{{\rm{ - 1}}}$ at 120 ℃ and 0.1 MPa H₂ can be obtained. The prepared Au/Cu-Al₂O₃ catalyst was found reusable and was effective to the concentrated furfural solution, as well as several typical unsaturated aldehydes.