Highly Dispersed and Stable Hydrotalcite-Derived NiCu/MgAlO Alloy Catalyst for Efficient Amination of Cyclohexanol to Cyclohexylamine in the Vapor Phase

Developing a mild and efficient method for highly selective amination of alcohols to amines as important versatile compounds is very interesting in the organic synthesis field. In this work, we have developed a simple and efficient approach for high-yield preparation of cyclohexylamine from the vapor-phase catalytic amination of cyclohexanol with ammonia under atmospheric pressure. The results indicated that the hydrotalcite-derived NiCu/MgAlO alloy catalyst exhibited excellent catalytic performance and stability, and 98% cyclohexanol conversion with 95% selectivity toward cyclohexylamine had still been maintained after running for over 300 h at 170 °C. The super high activity and stability of the NiCu/MgAlO catalyst are attributed to the active Ni–Cu alloy nanoparticles with high dispersion and uniform particle size (about 4 nm). DFT calculation results indicated the Ni site of the NiCu alloy (111) facet as the main catalytic active site. The energy profiles for the potential comparative free energy of cyclohexanol to cyclohexylamine on the NiCu alloy (111) facet were calculated. This approach employing a highly dispersed and stable Ni–Cu bimetallic alloy catalyst for efficient amination of cyclohexanol to cyclohexylamine in the vapor phase is promising and has potential industrial application prospects. Especially, the designed Ni–Cu alloy catalyst can also be applied in the amination of other alcohols with ammonia to prepare the corresponding organic amines.