Kinetic Studies on the Impact of Pd Addition to Ru/TiO₂ Catalyst: Levulinic Acid to γ‑Valerolactone under Ambient Hydrogen Pressure

The conversion of levulinic acid (LA) to γ-valerolactone (GVL) is one of the most important reactions from biomass-derived platform chemicals to value-added chemicals. In this work, bimetallic PdRu/TiO₂ catalyst compared to monometallic Ru/TiO₂ was designed for the conversion of LA to GVL at ambient H₂ pressure. The highly dispersed Pd affected the reaction by two antagonistic effects: (I) increasing the reaction rate by promoting the activation of H₂; (II) decreasing the reaction rate by lowering the activation ability of carbonyl group over Ru. The kinetic analysis refined by H₂ concentration showed much lower apparent activation energy over 0.2Pd1Ru/TiO₂ than that over Ru/TiO₂. Finally, the catalysts were evaluated by both GVL productivity and catalyst cost to show increasing benefit of Pd addition at lower H₂ pressure. This study offers both theoretical foundation and application instructions for high efficiency conversion of LA to GVL under mild conditions, especially ambient H₂ pressure.