Monometallic Ni, Co and Ru, and bimetallic NiCr, NiTi and CoFe Ziegler-Sloan-Lapporte catalysts for the hydrogenation of adiponitrile into hexamethylenediamine: Effect of water and dopants

The catalytic hydrogenation of adiponitrile into hexamethylenediamine (HMD) under mild conditions (20 bar H-2, 120 to 180 degrees C) using monometallic Ni, Co and Ru and bimetallic NiCr, NiTi, NiCo and CoFe Ziegler-type catalysts is reported. It is found that water exerts a strong negative influence on the selectivity to the primary amine HMD whereas it has a spectacular beneficial effect on the catalyst activity, especially for Ni based catalysts. Adding a second metal (Cr, Ti) as a dopant for nickel has a beneficial effect on the selectivity in HMD but results in lower activities. The ratio Ni/M (M = Cr, Ti) does not appear to be a key parameter in these systems as the doping effect on the HMD selectivity already appears at low dopant loading (atom.-%, 3% for Cr, 10% for Ti) and is constant up to 60%. The temperature has an influence on the HMD selectivity: the NiCr and NiTi catalysts show a peculiar behaviour, maintaining a high selectivity level (ca. 90%) over all the temperature range, This is not the case for the Co based catalysts.