Novel aqueous-phase hydrogenation reaction of the key biorefinery platform chemical levulinic acid into γ-valerolactone employing highly active, selective and stable water-soluble ruthenium catalysts modified with nitrogen-containing ligands

High catalytic activities (TOF = 3000 h(-1)) have been achieved by novel water-soluble ruthenium catalysts modified with nitrogen-containing ligands such as the bathophenanthrolinedisulfonic acid disodium salt (BPhDS) in the hydrogenation reaction of the renewable polar platform chemical levulinic acid (LA) which possesses a central relevance in the development of biorefineries of the future in a sustainable way to produce with essentially quantitative selectivity of 99.9 mol% gamma-valerolactone (GVL) in aqueous media. The apparent activation energy of the Ru/BPhDS catalyst was calculated and amounts a relative low value of 53.3 kJ/mol when one considers that in the LA h ydrogenation reaction this catalyst reduces a less reactive keto group into alcohol functionality. A recycling experiment of the Ru/BPhDS catalyst by extraction after addition of diethyl ether has shown that the catalyst is stable without loss of activity and selectivity in a consecutive run.