Aqueous-Phase Hydrogenation of Levulinic Acid Using Formic Acid as a Sustainable Reducing Agent Over Pt Catalysts Supported on Mesoporous Zirconia

Monometallic Pt catalysts supported on mesoporous (MP) ZrO2 were prepared and utilized as catalysts in the aqueous-phase upgrading of lignocellulosic biomass-derived levulinic acid (LA), with formic acid (FA) serving as a sustainable reducing agent. Among the studied catalysts, 1.6Pt/mesoporous ZrO2 showed the highest LA conversion (97%) and a gamma-valerolactone (GVL) yield (90%) at 513 K after 24 h of reaction was achieved. This high LA conversion and GVL yield obtained can be attributed to the high specific surface area (204 m(2) g(-1)) and density of acid sites (136 mu mol g(-1)) and Pt dispersion (37%). Furthermore, this catalyst exhibits high stability after 96 h of reaction time, that is, four catalytic repetitions, with a GVL yield above 60% and no change in the crystal structure of the support. A high reaction temperature (533 K) tends to shift the reaction equilibrium from GVL to pentanoic acid which is formed with a yield of 22% after 24 h. Even after increasing the complexity of the model mixture by adding vanillin (V) as a lignin-derived model compound to the aqueous solution of LA and FA, the catalyst remained stable and the hydrogenation of LA and V succeeded, resulting in 43% of GVL and 65% of 2-methoxy-4-methylphenol after 24 h at 513 K.