Production of Benzylamine by Tandem Dehydrogenation/Amination/Reduction over Cu and Au Catalysts

The feasibility of continuous synthesis of benzylamine from benzyl alcohol by tandem dehydrogenation/amination/reduction has been demonstrated over Cu/SiO2 and Au/TiO2. Both catalysts exhibited an equivalent metal particle size range (1-6 nm) and mean (3.1-3.2 nm, from STEM). Hydrogen chemisorption measurements revealed (five-fold) higher uptake on Au/TiO2 than Cu/SiO2 under reaction conditions. Reductive amination of benzaldehyde over Cu/SiO2 generated a 99% yield of dibenzylamine with no detectable benzylamine. Reaction of benzyl alcohol with NH3 (in N2) over Cu/SiO2 established utilisation of reactive hydrogen from alcohol dehydrogenation to convert intermediate imines to amines. Benzonitrile was the principal product due to the limited hydrogenation capacity of Cu. Inclusion of Au/TiO2 with Cu/SiO2 as a physical mixture promoted benzylamine formation and inhibited condensation-hydrogenation of benzylamine with benzaldehyde. Incorporation of H2 at low partial pressure (PH2 = 0.04 atm) in the feed and a lower reaction temperature (498 K → 448 K) enhanced benzylamine production.