Tartaric Acid-Assisted Synthesis of Well-Dispersed Ni Nanoparticles Supported on Hydroxyapatite for Efficient Phenol Hydrogenation

Developing highly active nonnoble-metal-based heterogeneous catalysts for selective hydrogenation is a long-sought goal due to the scarcity and high price of noble metals. Herein, well-dispersed and small-sized Ni nanoparticles (NPs) supported on hydroxyapatite (Ni-TA/HAP) were prepared using a simple tartaric acid (TA)-assisted impregnation method, which is based on the coupling interaction of strong electrostatic adsorption between the HAP and TA and reactive metal-ligand chelation between Ni and TA. Under mild conditions (e.g., 1 mol % Ni, 3 bar H-2 at 80 degrees C), the as-synthesized Ni-TA/HAP exhibited excellent activity and selectivity (>99%) for the efficient hydrogenation of phenolic compounds to the corresponding cyclohexanols, as well as the controlled partial hydrogenation of N-heteroarenes. Characterization results revealed that TA addition could promote a better dispersion of Ni species and inhibit the aggregation of Ni NPs during the fabrication of the Ni-TA/HAP catalyst. An optimal TA dosage (n(TA)/n(Ni) = 0.5) as well as a low Ni loading (1.0 wt %) coconstructed the favorable microstructure of the well-dispersed Ni nanoparticles as the catalytic center. The hydrogenation was boosted by small-sized Ni nanoparticles with a high ability for H-2 activation and HAP with both base and acid sites for appreciating phenol absorption.