Highly dispersed Ni/NiCaAlOx nanocatalyst derived from ternary layered double hydroxides for phenol hydrogenation: Spatial confinement effects and basicity of the support

Abstract

Mixed metal oxides derived from layered double hydroxides (LDHs) present favorable characteristics, mainly linked to the homogeneous distribution of the Ni species inside the lattice of metal oxides, resulting in ultrafine Ni(0) nanocatalysts. Herein, we report on the preparation and characterization of Ni/NiMAlOx (M = Ca, Mg or Zn) catalyst derived from ternary LDHs. These Ni catalysts were characterized by X-ray powder diffraction (XRD), transmission electron microscope (TEM), energy dispersive X-ray spectrometer (EDX), temperature-programmed reduction (TPR), and temperature-programmed desorption (TPD). For Ni/NiCaAlOx, the Ni particles were reduced in-situ and partially encapsulated by the NiCaAlOx support. The spatial confinement effects are beneficial to the metal-support interactions, which enhance the activity and catalytic stability of the Ni catalysts. The Ni/NiCaAlOx catalyst with strong basicity was highly active in phenol hydrogenation to cyclohexanol with a high TOF of 170 h−1; also, this catalyst was recycled 8 times without apparent loss of activity, thus demonstrating its good activity and stability. The pivotal roles of the spatial confinement effects and basicity of the support derived from ternary LDHs provide a viable strategy for the manufacture of highly active and stable non-precious metal catalysts.