Hydrogenation of Dinitrobenzenes to Corresponding Diamines Over Cu–Al Oxide Catalyst in a Flow Reactor

The catalytic hydrogenation of dinitroaromatic compounds is an important reaction for the production of phenylenediamine derivatives, which are widely used in industry. In this work, the catalytic properties of a Cu–Al mixed oxide obtained from double layered hydroxide have been investigated in liquid-phase hydrogenation of 1,3-dinitrobenzenes under continuous-flow conditions. The reaction was carried out at temperature of 120 °C, total pressure of 30 bar, using methanol or methanol/isopropanol mixture as a solvent. It was found that hydrogenation of 1,3-dinitrobenzene, 2,4-dinitrotoluene, 2,4-dinitroanisole and 2,4-dinitromesitylene provides the selective formation of the corresponding diamines, which were isolated in the form of salts with sulfuric acid stable in storage. The effect of the reaction temperature, pressure, H 2 flow rate, and solvent nature on the catalyst performance was studied. Graphical Abstract