Hydrogenation of levulinic acid to γ-valerolactone over anatase-supported Ru catalysts: Effect of catalyst synthesis protocols on activity

Abstract

γ-Valerolactone (GVL) is a value-added renewable chemical with great potential and can be obtained from biomass by the hydrogenation of levulinic acid (LA) using metal-based catalysts, such as Ru/TiO2. We here report an in depth study of the effect of catalyst synthesis parameters on the performance of Ru/TiO2 (anatase), varying the nature of the Ru-precursor and the conditions of the calcination and/or reduction step. Catalyst performance was evaluated under batch conditions at a hydrogen pressure of 45 bar and using either water (90 °C) or dioxane (150 °C) as solvent. The experiments showed that catalyst activity depends greatly on the Ru precursor used (RuCl3, RuNO(NO3)3, Ru(NH3)6Cl3). Best results when considering the turn-over frequencies (TOF) of the catalysts were obtained using the RuNO(NO3)3 precursor, whereas RuCl3 performed better when considering the initial rate based on Ru intake. An intermediate calcination step and the use of a hydrogen-rich sweep gas during the final reduction step were shown to have a negative impact on catalyst activity. Characterization of the fresh catalysts by BET and TEM provided valuable insight in the relation between the catalyst structure and its activity.