Temperature-Regulated N-Involved Ru Nucleation on Lignin-Derived Carbon for Enhanced Catalytic Transfer Hydrogenation of Levulinic Acid to γ-Valerolactone.

Sustainably sourced lignin presents great potential as carbon-based metal catalyst supports owing to its high carbon content as well as the ability to coordinate with metal ions. However, the rational regulation of the lignin-supported metal catalyst fabrication process to optimize their morphology and activity remains a challenge. Herein, we proposed a straightforward strategy to regulate the N content and species in the supports, thereby governing the nucleation behavior of Ru nanoparticles by varying the sintering temperature, for targeted enhancement of the catalytic performance of lignin-supported Ru-based catalysts. The sintering temperature of 700 °C was conducive to reducing the escape of elemental N and maintaining a high percentage of pyridinic-N species, which was beneficial to the adsorption and immobilization of Ru by the supports, resulting in the formation of Ru nanoparticles with a small size (1.93 nm). In the catalytic transfer hydrogenation (CTH) of levulinic acid (LA) to γ-valerolactone (GVL) using isopropanol as the hydrogen donor, the obtained catalyst demonstrated nearly 100% LA conversion and GVL selectivity under mild conditions (120 °C) with good reusability. This strategy achieves directional control over the structure of lignin-supported metal catalysts through a simple method, providing guidance for the efficient synthesis of these catalysts.