Synthesis of γ-valerolactone from ethyl levulinate hydrogenation and ethyl 4-hydroxypentanoate lactonization over supported Cu-Ni bimetallic, bifunctional catalysts

A stable and highly efficient supported Cu-Ni catalysts for the conversion of ethyl levulinate (EL) to γ-valerolactone (GVL) was developed. The catalysts were characterized by XRD, TEM, TPD, TPR, and XPS. The support effect of metal oxides (Al 2 O 3 , SiO 2 , ZrO 2 , and TiO 2 ) revealed that Cu-Ni supported on Al 2 O 3 showed the highest activity for EL hydrogenation to ethyl 4-hydroxypentanoate (EHP) and the subsequent intramolecular esterification of EHP to GVL. EHP intramolecular esterification to GVL in the ethanol solution was a reversible reaction with an equilibrium constant of 24 at 453 K. A simplified reaction kinetic network was established. The solvent had a significant influence on the reaction equilibrium and the catalyst stability. Cu-Ni/Al 2 O 3 in n-hexane solvent gave a higher GVL yield than that in ethanol solvent, and showed better recyclability than that in toluene solvent. With optimizing the conditions, Cu-Ni/Al 2 O 3 gave 99.9% conversion and 98% selectivity to GVL with a space–time yield of 1.13 g GVL g cat -1 h −1 in n-hexane solvent with good recyclability.