Catalytic hydrogenation of isophthalonitrile (IPN) over supported monometallic and bimetallic catalysts

Abstract

The hydrogenation of Isophthalonitrile (IPN) to meta-xylylenediamine (m-XDA) is usually catalyzed by RANEY® or supported Ni based catalysts in the presence of a basic additive. The supported catalysts have better mechanical strength and are safer than RANEY® Ni catalysts. This work aimed to study the catalytic performance of γ-Al₂O₃ supported Ni and Ni–M (M = Fe, Co, Cu) bimetallic catalysts in IPN hydrogenation. The H₂-TPR results revealed that the introduction of a second metal enhanced the reducibility of Ni catalyst. The Ni–M bimetallic catalysts also had different metal dispersion, electronic properties and adsorption strength. Among Fe, Co and Cu, Fe showed the best promoting effect, which was attributed to the strong N–metal bonding and weak H–metal adsorption strength, which enhanced the catalytic activity and m-XDA selectivity. The catalytic performance also strongly depended on the Ni–Fe mass ratio. For the γ-Al₂O₃ supported Ni and Ni–M catalysts with a low Ni loading of 5 wt%, the rate constant k_r increased from 0.024 mol^0.2 L^−0.2 min⁻¹ over 5Ni/Al₂O₃ to 0.033 mol^0.2 L^−0.2 min⁻¹ over 5Ni–1.67Fe/Al₂O₃, meanwhile the m-XDA selectivity increased from 34.7% to 49.5%. Over the Ni–Fe bimetallic catalyst with high metal loading, 20Ni–5Fe/Al₂O₃, a very high m-XDA selectivity of 99.9% was obtained.