Insights into the selective hydrogenation of levulinic acid to γ-valerolactone using supported mono- and bimetallic catalysts

Hydrogenation of levulinic acid (LA) towards gamma-valerolactone (GVL) is one of the most promising reactions in the field of biomass valorization to fine chemicals and liquid transportation fuels. Bimetallic Ni-Pt and Ni-Ru supported on ZrO2 and gamma-Al2O3 were successfully utilized in this work as highly active and GVL-selective catalysts for the solvent-free hydrogenation of levulinic acid (LA) using formic acid (FA) as a hydrogen source in a microwave reactor, with results further translated into a continues flow system to prove the reaction mechanism. The supported bimetallic catalysts and their corresponding monometallic counterparts were characterized using N-2-sorption, elemental analysis, X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS) and transmission electron microscopy (TEM). Under microwave irradiation, 100% selectivity to GVL was achieved using both mono- and bimetallic catalysts. Bimetallic Ni-Ru supported on gamma-Al2O3 shows the highest LA conversion (71%) among the studied catalysts. This high activity is attributed to a larger Ru degrees concentration on the surface of gamma-Al2O3 in comparison to ZrO2 as well as to the textural properties of y-Al2O3 (i.e., surface acidity, specific surface area). In contrast, ZrO2-based catalysts exhibited a higher stability with respect to gamma-Al2O3-based after four consecutive runs of reaction. (C) 2016 Elsevier B.V. All rights reserved.