Synergistic role of Cu0 and acidic sites in Cu/Al2O3 catalysts for enhanced furfural hydrogenation to furfuryl alcohol

The development of efficient catalysts for the selective hydrogenation of furfural (FAL) to furfuryl alcohol (FOL) is of great importance for sustainable chemical production. In this study, a highly efficient Cu/Al 2 O 3 catalyst was developed for the selective hydrogenation of FAL to FOL, achieving 100 % conversion and 100 % selectivity at 85 °C and 1.0 MPa H 2 with the optimal 7Cu/Al 2 O 3 -AIP catalyst, which was tailored by modulating the surface acidity of Al 2 O 3 and the distribution of Cu species. Evaluation of Cu-supported varying Al 2 O 3 catalysts revealed a near-linear correlation between the density of medium-strong acidic sites and catalytic activity, unequivocally demonstrating that medium-strong acidic sites on the alumina surface serve as the active sites for the reaction, which was further corroborated by competitive adsorption experiments involving pyridine and furfural. Furthermore, the density of Cu 0 sites was varied by adjusting the copper loading and conducting N 2 O selective oxidation experiments. Notably, a linear increase in catalytic activity was observed with the Cu 0 /(Cu 0  + Cu + ) ratio on the catalyst surface. Advanced characterization techniques, combined with experimental results, elucidated that the Cu 0 species act as the primary active sites for H 2 activation, while acidic sites are crucial for FAL adsorption, leading to the exceptional catalytic performance by the synergistic catalysis. This study underscores the synergistic effect between Cu 0 species and acidic sites, providing profound mechanistic insights into the FAL hydrogenation process and establishing a strategic foundation for the rational design of highly efficient Cu-based catalysts.