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Selective heterogeneous catalytic hydrogenations in liquid phase

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Ayshan Khalafli
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Previously, at the Department of Organic Chemistry and Technology of BME, a new method for selective liquid-phase heterogeneous catalytic hydrogenation of nitriles to primary amines was developed. Complete conversion, high isolated yield (90%) and selectivity to primary amine (95%) can be obtained in the hydrogenation of benzonitrile under mild reaction conditions (30 C, 6 bar), over a supported palladium catalyst (Pd/C), in a mixture of two immiscible solvents (water/dichloromethane) and in the presence of a medium acidic additive (NaH2PO4). Very pure product (>99% purity) can be achieved without applying any further purification procedures (e.g. distillation). During the course of my MSc-work, I have screened some carbon supported precious metal catalysts (10% Pd/C, 10%Pt/C, 5% Rh/C, 5% Ru/C and 5% Ir/C) and investigated the effects of the catalytic metals, temperature, catalyst/substrate ratio and solvents on the selectivity, isolated yield and the coversion of adiponitrile under the same conditions used in the palladium-catalysed hydrogenations of benzonitrile or benzyl cyanide. Under similar conditions, however, the palladium-catalysed hydrogenation of adiponitrile resulted in complete conversion with lower isolated yield (57%), but neither primary amine (1,6-hexamethylenediamine, HMDA) nor other important intermediate, 6-aminocapronitrile (ACN) was obtained.