Nickel phosphide and the role of supports on the performance of catalysts in the reductive amination reaction to synthesize 5-methyl-N-alkyl-2-pyrrolidone

Abstract

The effect of different supports (SiO₂, Al₂O₃, TiO₂, and ZrO₂) on nickel phosphide as an active phase in the reductive amination reaction (using aniline and octylamine) for the synthesis of 5-methyl-N-alkyl-2-pyrrolidone was studied. The experiments were conducted at 200°C and 50 bar H₂, using dioxane as the reactive solvent. Various techniques were employed to characterize the catalysts, including N₂ adsorption–desorption, H₂-temperature-programmed reduction (H₂-TPR), X-ray diffraction (XRD), pyridine-FTIR, and X-ray photoelectron spectroscopy (XPS). Firstly, the supports influenced the nickel species present on the surface and the number of acidic sites in each catalyst. Secondly, in the reaction between levulinic acid and aniline, the turnover frequency ($\mathrm{TO}{F}_{M_2\to 5M{P}_{\mathrm{anilina}}}$) for 5-methyl-1-phenyl-2-pyrrolidone production followed the order: NiP/Al₂O₃ > NiP/ZrO₂ > NiP/SiO₂ > NiP/TiO₂. Regarding the reaction between levulinic acid and 1-octylamine, the $\mathrm{TO}{F}_{L_1\to 5M{P}_{\mathrm{octylamine}}}$ for 5-methyl-N-octyl-2-pyrrolidone production followed the order: NiP/ZrO₂ > NiP/Al₂O₃ > NiP/SiO₂ > NiP/TiO₂. Finally, the supports influenced the type of nickel phosphide species present on the catalyst surface and, consequently, the hydrogenation rate to pyrrolidone molecules.