Tailoring metal dispersion of Pt/MgAl0.8O2.2 catalysts for furfuryl alcohol hydroconversion

Of the factors influencing the catalytic performance, the metal dispersion is of crucial importance, yet the specific effects and underlying interaction mechanism remain poorly understood. Herein, Pt/MgAl0.8O2.2 catalysts with Pt dispersion ranging from 43% to 62% were prepared via the ion-exchange strategy for the aqueous-phase hydroconversion of furfuryl alcohol to pentanediols. DFT calculations revealed that the volcano-type trend of Pt dispersion with the ion-exchange time prolonged was collectively driven by the electrostatic repulsion between [PtCl6]2- anions and hydrogen bonding among hydrolyzed [PtCl5OH]2- species. Increased Pt dispersion of resulting Pt/MgAl-t boosted the intrinsic catalytic activity of Pt sites, as evidenced by higher turnover frequencies, while the product distribution was almost identical irrespective of Pt dispersion. Kinetic studies demonstrated that the enhanced activity of Pt/MgAl-t catalysts could be related to decreased hydrogenation activation energies and promoted adsorption of furfuryl alcohol on highly dispersed Pt. Nevertheless, the adsorption configuration of furfuryl alcohol on Pt/MgAl-t was independent on Pt dispersion, ensuring invariable hydrogenation pathways and thereby resulting in consistent product selectivity. Pt/MgAl-12, featuring the highest Pt dispersion, delivered a furfuryl alcohol conversion of 99.9% and overall pentanediol selectivity of 78% by pressure-swing hydrogenation, outperforming most state-of-the-art metal catalysts. We anticipate that such a size-dependent performance relationship provides new insights into the catalytic behaviors of Pt in furfuryl alcohol hydroconversion.