Levulinic acid and its esters (e.g., ethyl levulinate, EL) are platform chemicals derived from biomass feedstocks that can be converted to a variety of valuable compounds. Reductive amination of levulinates with primary amines and H₂ over heterogeneous catalysts is an attractive method for the synthesis of N-alkyl-5-methyl-2-pyrrolidones, which are an environmentally friendly alternative to the common solvent N-methyl-2-pyrrolidone (NMP). In the present work, the catalytic properties of the different nickel phosphide catalysts supported on SiO₂ and Al₂O₃ were studied in a reductive amination of EL with n-hexylamine to N-hexyl-5-methyl-2-pyrrolidone (HMP) in a flow reactor. The influence of the phosphorus precursor, reduction temperature, reactant ratio, and addition of acidic diluters on the catalyst performance was investigated. The Ni₂P/SiO₂ catalyst prepared using (NH₄)₂HPO₄ and reduced at 600 °C provides the highest HMP yield, which reaches 98%. Although the presence of acid sites and a sufficient hydrogenating ability are important factors determining the pyrrolidone yield, the selectivity also depends on the specific features of EL adsorption on active catalytic sites.

The hydrogenation of the biomass platform compound, ethyl levulinate, for the synthesis of γ-valerolactone represents a highly promising pathway for biomass valorization. Transition metal phosphates are extensively utilized in biomass hydrogenation reactions due to their Brønsted and Lewis acid sites. In this study, we synthesized a series of transition metal (Ni, Co, and NiCo) phosphide catalysts using the liquid phase method. We investigated the effects of metal species and initial Co/Ni molar ratios on catalytic activity in hydrogenation of ethyl levulinate and optimized the reaction conditions. The NiCoP-1.00 sample, prepared with a Co/Ni molar ratio of 1, demonstrated high efficacy in the hydrogenation of ethyl levulinate to γ-valerolactone, achieving excellent selectivity (97.9%) under optimized conditions. Experimental findings indicate that the synergistic interaction between Ni and Co facilitates the hydrogenation of the intermediate ethyl 4-hydroxypentanoate to γ-valerolactone while inhibiting excessive hydrogenation. The catalytic performance of the NiCoP-1.00 catalyst remained stable over five recycling runs.