High-Performance Supported Ru Catalysts for the Aqueous-Phase Hydrogenation of Levulinic Acid to -Valerolactone

gamma-Valerolactone (GVL) can be obtained by efficient hydrogenation of levulinic acid using ruthenium-based catalysts in an aqueous medium. This paper reports an in-depth study on the activity and selectivity of Ru catalysts supported on zirconia-alumina, focusing on the effect of Ru concentration (0.5, 1.5 and 3 wt. % of Ru) and the selection of operational reaction variables. The results showed that the activity strongly depends on the number and oxidation state of the supported ruthenium particles. The most active catalyst, Ru3/ZA, presented the highest number of nanometric particles of zerovalent Ru and the highest number of acid sites. This catalyst gave ca. 100 % selectivity towards GVL, at high conversion of levulinic acid (over 99 %) under the best operating conditions evaluated (120 degrees C, 3 MPa H-2 pressure, 1 h of reaction, and 0.1 g of catalyst). In addition, this catalyst kept high levels of conversion and selectivity after successive reuse cycles.