Over 50 wt% loaded nanoparticulate Ru on hollow carbon spheres as efficient catalysts for the conversion of levulinic acid to γ-valerolactone under ambient conditions

Abstract

The conversion of biomass-derived levulinic acid (LA) to γ-valerolactone (GVL) is one of the key transformations for producing bio-fuel precursors. Although various Ru-based heterogeneous catalysts have been developed, these conversions typically required 0.25~2.8 mol% Ru for LA, high temperatures (~150 o C), and high H2 pressures (up to 50 bar). To enable more sustainable GVL production under milder reaction conditions, the development of more efficient catalysts is required. In this work, Ru nanoparticles supported on the hollow carbon spheres (Ru/HC) were successfully engineered using hollow microporous organic polymers (HMOPs) as templates. In particular, the coating of tannic acid on the HMOP facilitated the efficient incorporation of Ru species into the templating materials. The optimized 51.6 wt% Ru/HC-3 catalyst with 0.25 mol% Ru for LA exhibited excellent catalytic performance, achieving a 94% GVL yield and good recyclability at 100 o C under 5 bar H2. The excellent catalytic performance of Ru/HC-3 under mild conditions can be attributed to the unusually low reduction temperature (80 o C) of the surface RuOx species.