Metal-modified Ni phosphides: Highly efficient catalysts for the hydrogenation of ethyl levulinate

The hydrogenation of ethyl levulinate (EL) to γ-valerolactone (GVL) is an important process in biomass conversion to value-added chemicals. However, it remains challenging to develop efficient non-noble metal catalysts with high activity and selectivity for this reaction. Herein, we investigated the effect of second metal modification on Ni3P catalysts, where a series of Ni-P-M/Al2O3 and Ni-M/Al2O3 catalysts (M = Fe, Co, Cu, and Zn) were prepared for EL hydrogenation. The results show that Ni-P-Cu/Al2O3 exhibited the highest activity, being 2.3 and 1.7 times more active than Ni-Cu/Al2O3 and Ni-P/Al2O3, respectively. Reaction evaluations at different temperatures revealed that Ni-P/Al2O3 and Ni-P-Cu/Al2O3 have a similar activation energy of ∼65 kJ/mol, lower than that of Ni-Cu/Al2O3 (86 kJ/mol). The combined characterization and reaction results suggested that the introduction of Cu enriched surface P in the Ni-P-Cu/Al2O3 catalyst, providing more active sites to enhance CO hydrogenation. These findings provide insights for optimizing non-noble metal catalysts for EL hydrogenation.