Highly selective production of benzylamine from benzonitrile on metal-supported catalysts

Abstract

The selective liquid-phase hydrogenation of benzonitrile (BeN) to benzylamine (BeA) was investigated on silica-supported Ni, Co and Pd catalysts at 373 K and 13 bar H₂, using ethanol as a solvent. Ni/SiO₂ was more active and selective to BeA than Co/SiO₂ and Pd/SiO₂, yielding 78% of BeA and dibenzylamine (DBeA) as the only byproduct. The reaction was of positive order with respect to H₂ and BeN on Ni/SiO₂, but the selectivity to BeA did not change by increasing the reactant concentrations. In contrast, the BeA selectivity increased with the temperature. The effect of solvent on Ni/SiO₂ activity and selectivity was studied by using non-polar aromatic (toluene) and naphthenic (cyclohexane) hydrocarbons, and protic alcohols (methanol, ethanol). The highest BeA yield (92%) was obtained in methanol, without the addition of any additives. Ni/SiO₂ may be regenerated and reused after reaction, maintaining its catalytic selectivity performance at full BeN conversion.