Ag-doped Ni/SiO2 catalysts for the synthesis of aromatic amines from aromatic phenol†

Abstract

Aromatic primary amines are chemical products and raw materials with a wide range of applications. However, synthesis of primary aromatic amines relies heavily on non-renewable petrochemicals as feedstock. We have prepared a catalyst for Ni/SiO₂ doped Ag, and a process has been instituted to prepare aromatic primary amines, which use renewable resources as raw materials through a fixed bed reactor under ambient pressure conditions. The catalyst and process were validated using phenol synthesis of aniline as a template reaction. The resultant surface phenol conversion is 99% and aniline selectivity is 98.5%, and the by-product of the reaction is water, which is in line with the principles of green chemistry. The broad applicability of the catalysts and synthesis process was further verified by the synthesis of aromatic primary amines using the corresponding aromatic phenols. The catalysts were characterized using TEM, SEM, BET, XPS and XRD techniques to fully analyze their morphology, microstructure and elemental composition. The adsorption model was constructed based on the characterization results, and the density functional theory (DFT) calculations confirmed that after doping Ag, phenol formed shorter chemical bonds at the active site of Ni–Ag bimetal through chemical adsorption, which indicated that it had stronger adsorption energy for phenol, and the amount of electron transfer from the active site of Ni–Ag bimetal to phenol was 2.9 fold higher than that before doping, which significantly promoted the activation of reactants.