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

Abstract

Phenol 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/SiO 2 -AE) containing nickel nanoparticles and Lewis acid sites derived from nickel phyllosilicates for efficient amination of phenol to cyclohexylamine. The Ni/SiO 2 -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/SiO 2 -DP) and wetness-impregnation (Ni/SiO 2 -WI). The turnover frequencies based on the actual exposed metal surface area for Ni/SiO 2 -AE, Ni/SiO 2 -DP, and Ni/SiO 2 -WI are calculated as 71.7, 49.0, and 8.7 h À 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 Ni 2 + sites on the catalyst serve to adsorb and activate phenol. The synergistic effect of the dual-functions intensifies the phenol amination.

Influence of the preparation method on Ni/SiO2 catalysts for selective hydrogenation of succinic anhydride to γ-butyrolactone

“…Catalysts prepared via ammonia evaporation showed the highest activity and methane selectivity due to the ability to be activated at low temperatures. Liu 36 compared the performance of Ni/SiO 2 catalysts prepared via ammonia evaporation, deposition–precipitation and wetness-impregnation for selective amination of phenol to cyclohexylamine. The results indicated that Ni/SiO 2 catalysts prepared via different methods would lead to different Ni nanoparticle sizes and surface acidity.…”

The Acquisition of Primary Amines from Alcohols through Reductive Amination over Heterogeneous Catalysts

“…Liu et al [81] prepared a bifunctional Ni-based catalyst (Ni/SiO 2 -AE) containing nickel nanoparticles and Lewis acid sites derived from nickel phyllosilicates via a modified ammonia evaporation method and used it in the reductive amination reaction of phenol. As shown in Figure 4…”

“…[103]. Copyright 2018, Royal Society of Chemistry.Liu et al[81] prepared a bifunctional Ni-based catalyst (Ni/SiO2-AE) containing nickel nanoparticles and Lewis acid sites derived from nickel phyllosilicates via a modified ammonia evaporation method and used it in the reductive amination reaction of phenol. As shown in Figure4, the Ni/SiO2-AE catalyst enabled 89.4% phenol conversion and 86.0% selectivity for cyclohexylamine at 160 °C for 2 h, outperforming the catalysts formed via conventional deposition-precipitation (Ni/SiO2-DP) and wetness-impregnation (Ni/SiO2-WI).…”