Regulating the Interaction within Pd-Cu Dual Metal Sites for Selective Hydrogenation of Furfural Using Ambient H2 Pressure

Selective hydrogenation of furfural (FF) to furfuryl alcohol (FA) using ambient H2 pressure over a Cr-free catalyst is a sustainable upgrading process for cellulosic carbohydrates. The synergistic catalysis of dual metal sites is vital for selective activation of complex chemical bonds in biomass compounds. In this work, a Pd-CuOx nanocomposite catalyst was synthesized by a facile one-pot hydrolysis-precipitation method. For comparison, Pd/CuOx, Pd/Cu2O, and Pd/CuO supported-catalysts were prepared by the adsorption method. The Pd-CuOx catalyst showed 100% selectivity of FA with full conversion of FF at 120 °C under 1 bar of H2 within 4 h. The obtained initial reaction rate of FF (25 molFF molPd–1 h–1) and productivity of FA (72 molFA molPd–1 h–1) represented outstanding results in the literature. Besides, this catalyst exhibited remarkable stability during five consecutive reuses without metal leaching. It was disclosed that the valence state of Cu and Pd-Cu interactions played critical roles in determining the intrinsic activity of the prepared Pd-Cu catalysts. Various characterizations combined with kinetic experiments and in situ chemisorption clearly unraveled adsorption and activation processes of the C═O bond and H2 molecule on Pd0, Cu0, and Cu1+ sites. To the best of our knowledge, this work provided the first insight into synergistic catalysis for hydrogenation of FF over a Pd-Cu bimetallic catalyst.