Greener, Recyclable, and Reusable Ruthenium(III) Chloride/Polyethylene Glycol/Water System for the Selective Hydrogenation of Biomass-Derived Levulinic Acid to γ-Valerolactone

A versatile and efficient catalyst for the hydrogenation of biomass-derived levulinic acid to g-valerolactone (GVL) by using a RuCl3/polyethylene glycol (PEG-400) /H2O catalyst system was developed. The catalysis system was also found to be active for the hydrogenation of levulinate ester. The present protocol proceeded with 99% conversion and 99% selectivity towards GVL without the formation of any side products. Remarkably, the reaction did not require sensitive phosphine ligands, a base, additives, or a co-catalyst to promote the reaction. This method involved the use of environmentally benign PEG-400 and water as a solvent, which is nontoxic, inexpensive, commercially available, nonflammable, and easy to handle. The RuCl3/PEG-400/H2O catalyst system could be easily recycled and reused six times with high activity and selectivity.