Hydrogenation of the pivotal biorefinery platform molecule levulinic acid into renewable fuel γ-valerolactone catalyzed by unprecedented highly active and stable ruthenium nanoparticles in aqueous media

γ-Valerolactone (GVL) is a key downstream product of renewable biomass with enormous potential for the manufacture of advanced biofuels, bio-based chemicals, materials or for its direct use as an additive to gasoline and is obtained by the hydrogenation reaction of the important platform molecule levulinic acid (LA). Unprecedented high catalytic activities (TOF = 42530 h−1) have been achieved by water-dispersible ruthenium nanoparticles (RuNPs) stabilized by a broad spectrum of water-soluble polymers with both oxygen-containing functionalities such as the non-toxic and inexpensive polyethylene glycol (PEG) and poly(vinyl alcohol) (PVA) and with polymers bearing nitrogen-groups in the hydrogenation of LA to obtain with high selectivities (99.2 mol%) GVL in the aqueous medium. Furthermore, water provides for a desired higher dispersion of RuNPs catalysts capable to achieve high activities and impressive stabilities. The calculated apparent activation energy of the RuNPs/PEG catalyst amounts a low value of 32.3 kJ/mol. TEM investigations revealed the formation of RuNPs/PVA catalysts with a small average particle size diameter of 2.8 ± 0.1 nm which is consistent with the high catalytic activities. Recycling experiments have shown that the RuNPs/PVA catalyst demonstrated superb stability and selectivity in five consecutive runs at a high molar ratio LA/Ru = 16000 which is of industrial interest.