Selective Hydrogenation of Adiponitrile to Hexamethylenediamine by Supported Co Catalyst under Alkali-Free Conditions

Selective hydrogenation of adiponitrile (ADN) is an important strategy to produce high-value-added hexamethylenediamine (HMDA) that plays a crucial role in the development of engineering plastics. Herein, alkali-free catalytic hydrogenation of adiponitriles with a high yield of HMDA was conquered by supported Co catalysts with fine-tuned Co-support interaction. Characterizations including XRD, TEM, XPS, hydrogen temperature-programmed reduction/desorption experiments (H2-TPR / H2-TPD), and in situ FTIR spectroscopy of substrate were carried out to understand in-depth the specific selectivity toward HMDA modulated by structural advantages. The promoted H2 activation ability with the modulated electronic environment of Co/SiO2-400 was correlated with better alkali-free reactivity. It displayed 85.4% HMDA yields under a greatly reduced activation energy (56.9 kJ/mol) with a reaction rate constant k1 of 0.15 min–1. The catalyst maintains high catalytic stability even after 5 reaction cycles, which can be effectively applied for the hydrogenation of ADN to produce hexamethylenediamine under mild and alkali-free conditions.