A comparative study of magnetic bimetallic nanocatalysts for catalytic transfer hydrogenation of ethyl levulinate to γ-valerolactone

Abstract

In this study, we developed efficient nanocatalysts composed of Fe₂O₃/C-based bimetallic catalysts to employe in the catalytic transfer hydrogenation (CTH) of ethyl levulinate (EL) to γ-valerolactone (GVL) as a biomass valorization process. The surface acidity of the catalysts was determined through chromatographic titration with gas-phase adsorption of pyridine (PY) and 2,6-dimethyl pyridine (DMP). We systematically examined the impact of solvent, temperature, pressure, catalyst amount, and reaction time on γ-valerolactone (GVL) production efficiency. Under optimal conditions—0.4 g catalyst, 220 °C, 10 bar, and a 12-hour reaction time—conversion rates of 94 %, 96 %, and 89 % were achieved for the Co₃O₄/Fe₂O₃/C-based, NiO/Fe₂O₃/C-based, and MnO₂/Fe₂O₃/C-based catalysts, respectively. These catalysts also exhibited significant selectivity for γ-valerolactone (GVL), with selectivities of 95 %, 95 %, and 82 % for Co₃O₄/Fe₂O₃/C-based, NiO/Fe₂O₃/C-based, and MnO₂/Fe₂O₃/C-based, respectively. The magnetic nature of these catalysts facilitated easy separation post-reaction and they exhibited stable performance and reusability up to four cycles without significant loss of activity. Furthermore, the hot filtration test with no further conversion after catalyst removal showed that the active species were bound to the solid catalyst, confirming its stability and reusability under reaction conditions. Our results highlight these heterogeneous magnetic nanocatalysts as sustainable, environmentally friendly, and highly effective for the catalytic transfer hydrogenation of biomass-derived platform molecules to valuable chemicals.