Selective Amination of Phenol to Cyclohexylamine over Metal‐Acid Bifunctional Catalysts Derived from Nickel Phyllosilicates

Abstract

AbstractPhenol amination to various valuable amines has attracted considerable attention in heterogeneous catalysis, but limited studies have focused on non‐noble metal catalysts. This study reports a bifunctional catalyst (Ni/SiO2‐AE) containing nickel nanoparticles and Lewis acid sites derived from nickel phyllosilicates for efficient amination of phenol to cyclohexylamine. The Ni/SiO2‐AE catalyst resulted in 89.4% phenol conversion and 86.0% selectivity to cyclohexylamine at 160 °C for 2 h, which outperforms the catalysts by conventional deposition‐precipitation (Ni/SiO2‐DP) and wetness‐impregnation (Ni/SiO2‐WI). The turnover frequencies based on the actual exposed metal surface area for Ni/SiO2‐AE, Ni/SiO2‐DP, and Ni/SiO2‐WI are calculated as 71.7, 49.0, and 8.7 h−1, respectively. Results demonstrate that the Ni nanoparticles exsoluted from nickel phyllosilicates participate in the activation of dihydrogen molecules, and the Lewis acid sites stemmed from coordination unsaturated Ni2+ sites on the catalyst serve to adsorb and activate phenol. The synergistic effect of the dual‐functions intensifies the phenol amination.