Catalytic hydrogenation of <i>p</i>-nitroaniline and 2-methoxy-5-nitroaniline

Abstract

Catalytic hydrogenation of <i>p</i>-nitroaniline (PNA) to <i>p</i>-phenylenediamine (PPD) was carried out in methanol using 5% Pd/C as a catalyst at hydrogen pressures in the range of 200-1000 kPa, reaction temperatures 313-333 K, catalyst loadings 200-500 mg dm^-3 and PNA concentrations 0.3-1.02 mol dm^-3. Catalytic hydrogenation of 2-methoxy-5-nitroaniline (MNA) to 4-methoxy-1,3, benzenediamine (MBD) was carried out in dimethylformamide as a solvent using 5% Pd/C as catalyst at hydrogen pressures 1000-2000 kPa, reaction temperatures 413-433 K, catalyst loadings 200-600 mg dm^-3 and MNA concentrations 0.22-1.7 mol dm^-3. Speed of agitation beyond 17 rps had no effect on the progress of the reaction. The study shows that PNA and MNA can be selectively hydrogenated to PPD and MBD,

respectively and the initial rate of hydrogenations showed first order dependence on the reactant concentration, hydrogen partial pressure, and the catalyst loading for both the reactions. The activation energies for the catalytic hydrogenation of PNA and MNA were found to be 37.26 and 93.73 kJ mol^-1, respectively.