Synergistic effect of single atoms and clusters on boosting activity of TiO2-supported Pd catalysts towards total furfural hydrogenation

Abstract

Total furfural (FAL) hydrogenation to the industrially valuable tetrahydrofurfuryl alcohol (THFOL) involves the cascade hydrogenation of the formyl and furanic groups. However, supported metal catalysts are generally confronted with low activity, especially under mild conditions. Herein, we present a highly active Pd catalyst supported on TiO₂ with a Pd loading of 0.2 wt% (0.2Pd/TiO₂) for the efficient one-pot conversion of FAL to THFOL. Under mild conditions (25 °C, 60 bar H₂), 0.2Pd/TiO₂ achieves 90 % FAL conversion and 96 % selectivity to THFOL, outperforming the conventional high-Pd-content catalysts (e.g. 5 wt%Pd/TiO₂) and most reported catalysts. Detailed characterization and kinetic investigations reveal that the exceptional performance stems from the synergistic interplay between Pd single atoms and nanoclusters on the 0.2Pd/TiO₂ catalyst. Furthermore, kinetic studies highlight the crucial role of H₂O in promoting the desired reaction pathway. Impressively, 0.2Pd/TiO₂ demonstrates excellent stability, the activity and selectivity remain nearly identical even over seven consecutive reaction cycles. Moreover, the catalyst exhibits broad applicability, effectively hydrogenating various furanic compounds to the corresponding saturated products. This study provides key insights into the rational design of highly efficient and selective catalysts for tandem hydrogenation reactions.