Heterogeneous ru-based catalysts for one-pot synthesis of primary amines from aldehydes and ammonia

Abstract

The direct reductive amination of carbonyl compounds with NH3 and H2 is an alternative route to produce primary amines in practical production. The search for efficient and selective catalysts has attracted great interest. In the present work, the reductive amination of heptaldehyde with NH3 was investigated over a Ru-based catalyst. The product selectivities were found to be related with the supports of Ru. The alumina with spinel structure (γ-Al2O3, θ-Al2O3)-supported Ru catalysts exhibited selectivity favoring primary amines (94% yield) at 100% heptaldehyde conversion under optimal conditions. Purely basic (MgO, CaO) and relative acidic (Nb2O5, SnO2, MCM-41, HZSM-5) supports showed relatively poor selectivity towards primary amines (0%–53% yield). The reductive amination mechanism was also proposed. The Schiff base N-[heptylene]heptyl-1-amine was a key intermediate. Ru/γ-Al2O3 was shown to be an excellent hydrogenolysis catalyst to selectively produce primary amine by amination and hydrogenolysis of N-[heptylene]heptyl-1-amine.