Continuous reductive amination to synthesize primary amines with high selectivity in flow

Reductive amination, a convenient way to convert carbonyl compounds into corresponding amines, gains increasing attention in the amine production. In this work, we propose a continuous reductive amination process in a micropacked bed reactor using nickel catalysts. The reductive amination of benzaldehyde is chosen as the model reaction to elucidate the effects of catalyst/support, solvent, temperature, the molar ratio of ammonia to benzaldehyde, pressure, and concentration. A high 99% yield of benzylamine is obtained under mild conditions, with less ammonia addition and shorter reaction time. Furthermore, a kinetic network for the reductive amination of benzaldehyde is established, and the rate-determining step is determined. Besides, satisfied yields (90–99%) were also obtained when applying this method to various substrates, including aromatic and aliphatic aldehydes, ketones, and biomass derivative furfural.