Zirconium-Gallic Acid Coordination Polymer: Catalytic Transfer Hydrogenation of Levulinic Acid and Its Esters into γ-Valerolactone

The conversion of ethyl levulinate (EL) to produce γ-valerolactone (GVL) through catalytic transfer hydrogenation (CTH) reaction plays a crucial role in the field of biomass catalytic conversion. In this work, a novel Zr-base catalyst with phenate group, phenolic hydroxyl and carboxyl in its structure was prepared by the co-precipitation of natural sources gallic acid and ZrCl4. It was found that Zr-GA has an excellent catalytic performance for this reaction and satisfactory GVL yield could be achieved. Besides, Zr-GA could be easily separated from the reaction system and reused at least six times without a significantly decrease in activity. Meanwhile, various characterizations had proved that Zr-GA is a porous material with acid–base bifunctional sites. The main reason for the high catalytic activity of the Zr-GA was that the synergetic effects of Lewis acid/base sites and Bronsted acid sites and appropriate textural properties. In addition, a possible reaction mechanism was proposed in conjunction with the poisoning experiment and previous reports. The heterogeneous catalyst Zr-GA prepared with gallic acid as a raw material has low cost and recyclability, and has great potential in green chemistry.