Improved Catalytic Transfer Hydrogenation of Biomass-Derived Aldehydes with Metal-Loaded Aluminum Phosphate

Catalytic transfer hydrogenation (CTH) is a benign and effective process for the conversion of biomass-derived platforms into fuels and chemicals. Here, aluminum phosphate (Al/P ratio = 1.5) (APO1.5) and alkali earth metal (AEM)-loaded APO1.5s were synthesized by impregnation and applied in the CTH of furfural (FF) into furfuryl alcohol (FA). The introduction of AEM created weak and medium basic sites instead of weak acidic and strong basic sites in the pristine APO1.5, allowing co-catalysis of the AEM oxide species (basic sites) and the APO1.5 (acidic sites) to facilitate hydrogenation instead of etherification and acetalization. For 3 wt % Ca/APO1.5, this tuning of acidity and basicity improved the FA yield significantly from 54 to 90% (140 °C, 48 h), and the catalyst remained stable as well as reusable for at least four consecutive reactions with only slight deactivation. Notably, 3 wt % Ca/APO1.5 catalyst also showed high catalytic activity for CTH of other bio-derived aldehydes, thus demonstrating its versatile use for valorization of platforms generated during biomass refining.