Acid-Functionalized Mesoporous Carbon: An Efficient Support for Ruthenium-Catalyzed gamma-Valerolactone Production

The hydrogenation of levulinic acid has been studied using Ru supported on ordered mesoporous carbons (OMCs) prepared by soft-templating. P- and S-containing acid groups were introduced by postsynthetic functionalization before the addition of 1% Ru by incipient wetness impregnation. These functionalities and the reaction conditions mediate the activity and selectivity of the levulinic acid hydrogenation. The presence of S-containing groups (Ru/OMC-S and Ru/OMC-P/S) deactivates the Ru catalysts strongly, whereas the presence of P-containing groups (Ru/OMC-P) enhances the activity compared to that of pristine Ru/OMC. Under mild conditions (70 degrees C and 7 bar H-2) the catalyst shows high selectivity to gamma-valerolactone (GVL; > 95%) and high stability on recycling. However, under more severe conditions (200 degrees C and p(H2) = 40 bar) Ru/OMC-P is particularly able to promote GVL ring-opening and the consecutive hydrogenation to pentanoic acid.