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 H2 at 80 °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 (nTA/nNi = 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 H2 activation and HAP with both base and acid sites for appreciating phenol absorption.