Nickel Nanoparticles on Hydroxyl and Defect-rich Hollow Carbon Spheres as Catalysts for Efficient Selective Hydrogenation of Phenol

The development and design of high-performance catalysts for selective hydrogenation of phenol to high value-added cyclohexanol is challenging. A series of hollow carbon coated Ni nanoreactor catalysts (Ni@HCS-T) were synthesized, adjusting carbonization temperature to investigate the effect of chemical microenvironment on the performance of selective hydrogenation of phenol. The results confirmed the carbonization temperature can regulate the degree of carbon skeleton defects and hydroxyl functional group content on the catalysts. The optimum catalyst (Ni@HCS-800) catalyzed phenol conversion of 99.54% and cyclohexanol selectivity of 98.53% at 120 ℃, 2 h and 1 MPa H₂ under the carbonization at 800 ℃. The Ni@HCS-800 catalyst is rich in defective structures which, together with neighbouring hydroxyl groups, significantly enhance substrate adsorption. Meanwhile, the abundant defects reasonably modulate the interfacial charge transfer behavior, resulting in a significantly enhanced degree of electron transfer between the metal Ni and carrier, enhancing the interaction between carbon carrier and metal. The Ni@HCS-800 catalyst showed the activation energy E_a of 46.05 kJ⋅mol⁻¹ and remained stable performance after five cycles. In addition, the catalyst could effectively catalyze the conversion of a variety of lignin derivatives, showing wide applicability.