γ-Valerolactone (GVL), readily obtained by the hydrogenation of levulinic acid (LA), has been identified as a sustainable platform chemical for the production of both biofuels and bio-based chemicals. Here, we report recent efforts aimed at the development of new Ru-based catalysts for the conversion of levulinic acid to GVL, focusing on the influence of the choice of support, the synthesis method, choice of metal(s) and the influence of feed impurities. For example, alloying of Ru with Pd by a modified impregnation method, provided us with a supported nano-alloy catalyst showing exceptional productivity [1]. Extensive characterization with advanced microscopic and spectroscopic techniques provided insight into the interaction of the metal with support and in the nature of nano-alloys formed. The Ru-Pd/TiO2 catalyst not only outperformed previously reported (Ru-based) heterogeneous catalysts in terms of activity, it also showed excellent, sustained selectivity to GVL. Dilution and isolation of Ru active sites by Pd is thought to be responsible for this superior catalytic performance. We also compared the activity, selectivity, and stability of Ru-based catalysts supported on TiO2, ZrO2, and C in the conversion of LA to GVL in dioxane as solvent [2]. All catalysts show high GVL yields under standard conditions; however, large differences were seen in catalysts stability. The Ru/ZrO2 catalyst was found to perform better than the benchmark Ru/C and Ru/TiO2 catalysts, with the Ru/ZrO2 catalyst displaying high activity, selectivity, and stability upon repetitive recycling. Ru/TiO2 showed considerable deactivation upon reuse, which was attributed to the reduction of the TiO2 support resulting in a detrimental strong metal-support interaction. Furthermore, again in strong contrast to the benchmark catalysts, Ru/ZrO2 can efficiently perform the hydrogenation of LA in the presence of H2SO4, a likely process impurity, in the LA feed. The stability of the Ru-based catalysts in the presence of other biogenic and process-derived impurities was also assessed, providing insights into the (in)sensitivity of common hydrogenation catalysts to impurities expected in real LA feeds.

Ru-based heterogeneous catalysts for levulinic acid hydrogenation: On the influence of catalyst composition, synthesis and feed impurities

253rd National Meeting (2017)

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