Selective Hydrogenation of 5-Hydroxymethylfurfural to 5‑Hydroxymethyltetrahydrofurfural Over Heterogeneous Pd Catalyst Under Mild Conditions

Graphical The Pd/ZrO 2 catalyst prepared by the impregnation reduction method showed excellent activity and selectivity in the synthesis of HMTHF via the selective hydrogenation of the furan ring in 5-HMF at ambient hydrogen pressure and room temperature. Furthermore, the influence of the type of active hydrogen species on the hydrogenation of furan rings was proved by hydrogen spillover experiments. 5-Hydroxymethylfurfural (5-HMF) derived from lignocellulose represents an important platform molecule that could be employed in the selective hydrogenation of the furan ring to prepare 5‑hydroxymethyltetrahydrofurfural (HMTHF). However, the reported catalytic systems for the synthesis of HMTHF using 5-HMF still require additional hydrogen pressure. In this study, the Pd/ZrO 2 catalyst with uniformly dispersed Pd nanoparticles was prepared via a simple impregnation reduction process. This catalyst exhibited excellent catalytic activity and selectivity for the hydrogenation of 5-HMF to HMTHF. High HMTHF yields up to 92.3% were produced under mild reaction conditions of ambient hydrogen pressure and room temperature in methanol solvent. This result was superior to the most catalytic systems that had been reported so far. The mechanism study revealed that the active hydrogen species on the surface of the Pd nanoparticles and the reaction solvent in this study were the pivotal factors influencing the hydrogenation of furan rings in 5-HMF.