Synthesis of fine chemicals by selective hydrogenation of unsaturated nitriles

DARÍO J. SEGOBIA; ANDRÉS F. TRASARTI; CARLOS R. APESTEGUÍA

Lyon

Congreso; 11th International Congress on Catalysis and Fine Chemicals CAFC 11; 2016

The liquid-phase hydrogenation of unsaturated nitriles is an important route to obtain unsaturated primary amines that are valuable intermediates in agrochemical, pharmaceutical, and fine chemicals industries. Nevertheless, the selective hydrogenation of the C≡N group in unsaturated nitriles is still a challenging objective in heterogeneous catalysis1. In general, the hydrogenation of unsaturated nitriles may form three types of products:unsaturated amines (hydrogenation of C≡N bond), saturated nitriles hydrogenation of C=C bond) and saturated amines (hydrogenation of C=C and C≡N bonds). Besides, in order to obtain selectively primary amines, the coupling reactions leading to secondary and tertiary amines have to be avoided. Ammonia is often employed to suppress the formation of higher amines by shifting equilibrium to the primary amine since ammonia is released in the coupling reactions leading to secondary and tertiary amines; nevertheless, the addition of ammonia entails concerns related to corrosion and disposal of spent base materials. In this work, we investigate the selective hydrogenation of cinnamonitrile (CN) tocinnamylamine (CA) on silica-supported Co, Ni, Ru and Cu metals. As shown in Figure 1, CN may be initially hydrogenated in the C=C bond to yield hydrocinnamonitrile (HCN) or in the C N group producing CA, probably via the formation of an imine intermediate (cinnamylimine). CA may then react with the imine intermediate to form by deamination the unsaturated secondary aminedicinnamylamine (DiCA) and partially unsaturated secondary amine hydrocinnamyl-cinnamylamine (HCCA). Otherwise, CA may be hydrogenated to the saturated primaryamine (hydrocinnamylamine, HCA). Similarly, in parallel pathways, HCN may be hydrogenated to HCA or it may react with the imine intermediate (hydrocinnamylimine) to produce by deamination the saturated secondary amine (dihydrocinnamylamine, DiHCA) and partially unsaturated amine HCCA. The activity and selectivity of silica-supported Ni, Co, Ru and Cu catalysts for ydrogenating CN to CA greatly depend on the nature of the metal and reaction operating conditions. We report here that Cu/SiO2 catalysts remarkably promotes the selective formation of CA from cinnamonitrile, thereby yielding 74%of CA at 403 K and 40 bar H2, in absence of ammonia.