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

Abstract

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 γ-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 m2 g–1) and density of acid sites (136 μmol 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.