Catalytic hydrogenation of 1,4-phenylenediamine to 1,4-cyclohexanediamine

Catalytic hydrogenation of 1,4-phenylenediamine to 1,4-cyclohexanediamine using Ru/Al₂O₃ as a catalyst was carried out in water, and the results were compared with those in isopropanol and SC-CO₂. 80% 1,4-phenylenediamine conversion with 87% selectivity to 1,4-cyclohexanediamine was achieved on 5% Ru/Al₂O₃ catalyst at 90°C and H₂ pressure of 4 MPa. The hydrogenation of 1,4-phenylenediamine is influenced by the solvent. A systematic study of the hydrogenation of 1,4-phenylenediamine revealed that the reaction was consecutive. The longer the time, the lower was the CHDA selectivity. Also, the reaction temperature was an important parameter and played a vital role in preventing the formation of side products.