Reductive amination of 1,6-hexanediol with Ru/Al2O3 catalyst in supercritical ammonia

Hexamethylenediamine (HMDA) is an important reagent for the synthesis of Nylon-6,6, and it is usually produced by the hydrogenation of adiponitrile using a toxic reagent of hydrocyanic acid. Herein, we developed an environmental friendly route to produce HMDA via catalytic reductive amination of 1,6-hexanediol (HDO) in the presence of hydrogen. The activities of several heterogeneous metal catalysts such as supported Ni, Co, Ru, Pt, Pd catalysts were screened for the present reaction in supercritical ammonia without any additives. Among the catalysts examined, Ru/Al2O3 presented a high catalytic activity and highest selectivity for the desired product of HMDA. The high performance of Ru/Al2O3 was discussed based on the Ru dispersion and the surface properties like the acid-basicity. In addition, the reaction parameters such as reaction temperature, time, H-2 and NH3 pressure were examined, and the reaction processes were discussed in detail.