Unveiling the role of Ni-Re catalyst on diverse supports for efficient hydrogenation of levulinic acid to γ-valerolactone under near atmospheric H2 pressure

Abstract

The catalytic hydrogenation of levulinic acid to the important biomass-derived platform chemical γ-valerolactone was examined systematically under near-atmospheric H<inf>2</inf> pressure using a set of bimetallic Ni-Re catalysts supported on TiO<inf>2</inf>, MCM-41, Al<inf>2</inf>O<inf>3</inf>, ZSM-5, and MgAl hydrotalcite. Catalysts were prepared by an incipient wetness impregnation and were thoroughly characterized by comprehensive methods. Among the catalysts studied, Ni-Re/MgAl performed the best with 100 % conversion of LA and 95 % yield of GVL at 200 °C, 2 h, and 1 bar H<inf>2</inf>. The enhanced catalytic performance was ascribed to the combined effect of Re and Ni metals together with the distinctive properties of the MgAl support, which facilitated H<inf>2</inf> adsorption capacity, strengthened metal-support interactions, and provided significant acidity. Systematic kinetic studies asserted pseudo-first-order kinetics with the maximum rate constant (k = 0.0119 min⁻¹) for Ni-Re/MgAl. The impact of support properties on reducibility of metals, acidity, particle size, and reaction mechanism was described. The catalyst demonstrated very high activity under low-hydrogen pressure. The results validate the key role played by the support–metal interaction in maximizing bifunctional catalytic systems towards the valorization of biomass under mild conditions.