Propanol Amination over Supported Nickel Catalysts: Reaction Mechanism and Role of the Support

Ni-supported hydroxyapatite catalyst (Ni/HAP) was characterized and evaluated for propanol amination to propylamine at 423 K. The reaction proceeds via dehydroamination, a process that involves sequential dehydrogenation, condensation, and hydrogenation. Kinetic and isotopic studies indicate that alpha-H abstraction from propoxide species limits the rate of the dehydrogenation step and hence the overall rate of reaction. The rate of propanol dehydrogenation depends on the composition of the support and on the concentration of Ni sites located at the interface between Ni nanoparticles and the support. Ni/HAP is an order of magnitude more active than Ni/SiO2 and displays a higher selectivity toward the primary amine. The superior performance of Ni/HAP is attributed to the high density of basic sites on HAP, which are responsible for stabilizing alkoxide intermediates and suppressing the disproportionation and secondary amination of amines.