Catalyst and Process for the Synthesis of Adiponitrile via Catalytic Amination of 6-Hydroxyhexanenitrile from ε-Caprolactone

Abstract

Adiponitrile, as an important bulk chemical, was synthesized in two steps: catalytic amination of ε-caprolactone to 6-hydroxyhexanenitrile over a ZnO catalyst through a patented process, followed by catalytic amination of 6-hydroxyhexanenitrile to adiponitrile. An Al2O3-MgO composite-supported bimetallic catalyst Ni30Fe10/Al2O3-MgO(0.8:1.2)-700-2 was found to be efficient in the catalytic amination of 6-hydroxyhexanenitrile to adiponitrile. Under the optimal reaction conditions, which are a reaction temperature of 300 °C, atmospheric pressure, 6-hydroxyhexanenitrile/NH3/H2 molar ratios of 1:5:2, and a residence time of 5 s, the conversion of 6-hydroxyhexanenitrile reached 63.1% with an adiponitrile selectivity of 51.5%, corresponding to a one-pass adiponitrile yield of 32.5%. The characterization results revealed that Ni and Fe are present in the form of Ni3Fe alloy nanoparticles with diameters of 8 to 16 nm in the catalyst Ni30Fe10/Al2O3-MgO(0.8:1.2)-700-2. The good catalysis of Ni30Fe10/Al2O3-MgO(0.8:1.2)-700-2 could be ascribed to the synergetic effect between the two metals in the Ni3Fe alloy and a suitable magnesium-to-aluminum molar ratio in the catalyst. Catalyst deactivation took place due to the deposition of carbonaceous substances on the surface of the catalyst in a catalytic run, and the deactivated catalyst could be regenerated fully by high-temperature reduction with H2.