Efficient selective hydrogenation of N,N-dimethylaniline in a continuous fixed-bed reactor over a Cu/Ni–Al2O3 catalyst

Abstract

A series of Cu-modified Ni–Al₂O₃ catalysts with various Cu/Ni ratios (xCu/Ni–Al₂O₃) were prepared, and systematically characterized using BET, XRD, SEM, H₂-TPR, H₂-TPD, TG, and XPS. The catalyst exhibited excellent catalytic performance in the selective hydrogenation of N,N-dimethylaniline to N,N-dimethylcyclohexylamine in a continuous fixed-bed reactor. When the Cu/Ni molar ratio was 0.1, the active components were highly dispersed on the Al₂O₃ support, which possessed a high specific surface area and well-developed porous structure. Furthermore, the catalyst demonstrated strong hydrogen desorption capacity and enhanced thermal stability. Synergistic electronic interactions between Ni and Cu improved the adsorption and activation of both reactant and H₂ molecules. The incorporation of Cu near the Ni active sites effectively modulated the selectivity toward the desired product N,N-dimethylcyclohexylamine. Under the optimal reaction conditions: H₂ pressure of 5 MPa, reaction temperature of 130 °C, liquid hourly space velocity 0.1 h⁻¹ and hydrogen-amine volume ratio of 5500 : 1, the 0.1Cu/Ni–Al₂O₃ catalyst achieved superior performance, with a N,N-dimethylaniline conversion rate of 99.5% and a selectivity for N,N-dimethylcyclohexylamine of 97.6%.