Thermally-stable single-site Pd on CeO2 catalyst for selective amination of phenols to aromatic amines without external hydrogen.

Abstract

Developing a new route to produce aromatic amines as key chemicals from renewable phenols is a benign alternative to current fossil-based routes like nitroaromatic hydrogenation, but is challenging because of the high dissociation energy of the Ar-OH bond and difficulty in controlling side reactions. Herein, an aerosolizing-pyrolysis strategy was developed to prepare high-density single-site cationic Pd species immobilized on CeO2 (Pd1/CeO2) with excellent sintering resistance. The obtained Pd1/CeO2 catalysts achieved remarkable selectivity of important aromatic amines (yield up to 76.2%) in the phenols amination with amines without external hydrogen sources, while Pd nano-catalysts mainly afforded phenyl-ring-saturation products. The excellent catalytic properties of the Pd1/CeO2 are closely related to high-loading Pd single-site catalysts with abundant surface defect sites and suitable acid-base properties. This report provides a sustainable route for producing aromatic amines from renewable feedstocks.