Selective conversion of levulinic acid to gamma-valerolactone over Ni-based catalysts: Impacts of catalyst formulation on sintering of nickel

Abstract

Selective production of γ-valerolactone (GVL) from hydrogenation of levulinic acid (LA) is challenging over non-noble metal catalysts but attractive due to the promising application of GVL as platform chemical. In this study, Ni catalysts supported on Mg-Al and Ni-Al layered double hydroxides (LDH) were synthesized for hydrogenation of LA. LDH as the precursor could create developed porous structure and facilitate dispersion of Ni species. These factors together achieved selective conversion of LA to GVL with maximum yield of 99% over the 2.25Ni-0.75Mg-Al catalyst. The Ni-based catalysts are not active for the ring-opening of GVL. Mg and Al together in 2.25Ni-0.75Mg-Al suppressed the sintering of nickel species in ethanol, achieving much superior reusability to Ni-Mg. However, in water, the transformation of MgO in either Ni-Mg or 2.25Ni-0.75Mg-Al to amorphous Mg(OH)2 led to the collapse of pore structure and remarkable deactivation of the catalysts, while Ni-Al without Mg species performed much better.