Sustainable metal-lignosulfonate catalyst for efficient catalytic transfer hydrogenation of levulinic acid to γ-valerolactone

Production of γ-valerolactone (GVL) from biomass-derived platform levulinic acid (LA) via catalytic transfer hydrogenation (CTH) over renewable lignosulfonate-derived catalyst is reported herein. Lignosulfonate-derived catalysts were prepared by assembled Zr-metals with sodium lignosulfonate (LigS) derived from the industry paper waste. The resulting Zr-LigS catalyst exhibited excellent catalytic performance in 92.5% GVL yield under mild conditions. With the combination of detail catalyst characterizations, catalytic performance of the Zr-LigS catalyst, in-situ ATR-FTIR and poisoning experiments, the hydrothermal treatment of Zr4+ and LigS resulted in the formation of basic sites, which contributed significantly to the CTH reaction. Kinetic experiments demonstrated that the activation energy was as low as 41.9 kJ/mol. Furthermore, isotopic labeling experiments suggested that the β-H in isopropanol is transferred to the CO bond of LA by the formation of six-membered intermediates on the basic sites, which is the rate-determining step.