Hydrogenation of 4-Nitroacetophenone Over Rh/Silica: Understanding Selective Hydrogenation of Multifunctional Molecules

The hydrogenation of 4-nitroacetophenone (4-NAP) and 4-aminoacetophenone (4-AAP) was examined over a rhodium/silica catalyst at 333 K and 4 barg. High selectivities and yields (94 %) to 4-aminoacetophenone and 1-(4-aminophenyl)ethanol could be obtained from 4-NAP hydrogenation but high selectivity to 1-(4-aminophenyl)ethanol could not be obtained from direct 4-AAP hydrogenation. Addition of 4-methylcyclohexylamine modified the strength of adsorption and hence increased the rate of hydrogenation of both 4-NAP and 4-AAP and enhanced selectivity.