Cobalt catalysts: very efficient for hydrogenation of biomass-derived ethyl levulinate to gamma-valerolactone under mild conditions

Hydrogenation of ester levulinate to gamma-valerolactone (GVL) is an interesting reaction in biomass conversion to produce value-added chemicals. Exploration of efficient and robust catalysts is crucial for large-scale application. In this work, we conducted the reaction catalyzed by a Co catalyst, and it was found that commercially available Co3O4 was very efficient for this reaction under mild conditions after reduction by H-2. The effects of temperature, hydrogen pressure, amount of the catalyst used, and reaction time on the yield of GVL were studied. Under optimized conditions, the yield of GVL could reach 98%. The catalyst could be reused at least 10 times without notable toss of the activity and selectivity. The catalyst was characterized by scanning electron spectroscopy (SEM), transmission electron spectroscopy (TEM). X-ray photoelectron spectroscopy (XPS), and powder X-ray diffraction (XRD). It was demonstrated that the metallic Co-0 was the active species for the hydrogenation reaction. As far as we know, this is the first work conducting the reaction using Co as the catalyst.