Chemoselective hydrogenation of unsaturated nitriles to unsaturated primary amines: Conversion of cinnamonitrile on metal-supported catalysts

The liquid-phase hydrogenation of cinnamonitrile to selectively obtain the unsaturated primary amine (cinnamylamine) was studied at 383 K and 13 bar on Ni, Co, Ru and Cu metals supported on a commercial silica. Ni/SiO2 and Co/SiO2 were the most active catalysts for cinnamonitrile conversion but formed only small amounts of cinnamylamine. In contrast, Cu/SiO2 and Ru/SiO2 presented low activity for cinnamonitrile hydrogenation but formed selectively cinnamylamine in the liquid phase; nevertheless, on both samples the carbon balance was only about 40%. In an attempt of promoting the rate and yield to cinnamylamine, additional catalytic runs were carried out at higher temperatures and H2 pressures on a highly dispersed Cu(11%)/SiO2 catalyst prepared by the chemisorption–hydrolysis method. Results showed that when cinnamonitrile hydrogenation was performed at 403 K and 40 bar on Cu(11%)/SiO2, the yield to cinnamylamine was 74% giving as by-product only the unsaturated secondary amine (dicinnamylamine).

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