Mixed oxides supported low-nickel formulations for the direct amination of aliphatic alcohols with ammonia

The present study focuses on the selective synthesis of primary amines from aliphatic alcohols and ammonia using alumina-ceria supported nickel formulations based on very low nickel loading (<= 2 wt%) and without any additive or external H-2 supply. The effect of the catalyst preparation methods and modes of nickel impregnation were studied in detail and comprehensively characterized. The best formulation afforded 80% n-octanol conversion with 78% selectivity to n-octylamine at optimized reaction conditions, which were far better than control catalysts and benchmark Ni-alumina formulations relying on high Ni loadings. The enhanced activities of the alumina-ceria supported nickel catalysts was attributed to three combined effects: (1) a higher reducibility of surface nickel oxide species, (2) the genesis of very small and homogeneously distributed nickel nanoparticles (2-3 nm), and (3) a strong decline in the formation of nickel aluminates. Furthermore, unlike benchmark Ni catalysts, these formulations afforded a higher resistance to leaching. (C) 2017 Elsevier Inc. All rights reserved.