Reductive amination of ethanol to ethylamines over Ni/Al2O3 catalysts

Abstract

Ni(x)/Al2O3 (x=wt%) catalysts with Ni loadings of 5–25 wt% were prepared via a wet impregnation method on an γ-Al2O3 support and subsequently applied in the reductive amination of ethanol to ethylamines. Among the various catalysts prepared, Ni(10)/Al2O3 exhibited the highest metal dispersion and the smallest Ni particle size, resulting in the highest catalytic performance. To reveal the effects of reaction parameters, a reductive amination process was performed by varying the reaction temperature (T), weight hourly space velocity (WHSV), and NH3 and H2 partial pressures in the reactions. In addition, on/off experiments for NH3 and H2 were also carried out. In the absence of NH3 in the reactant stream, the ethanol conversion and selectivities towards the different ethylamine products were significantly reduced, while the selectivity to ethylene was dominant due to the dehydration of ethanol. In contrast, in the absence of H2, the selectivity to acetonitrile significantly increased due to dehydrogenation of the imine intermediate. Although a small amount of catalyst deactivation was observed in the conversion of ethanol up to 10 h on stream due to the formation of nickel nitride, the Ni(10)/Al2O3 catalyst exhibited stable catalytic performance over 90 h under the optimized reaction conditions (i.e., T=190 °C, WHSV=0.9 h−1, and EtOH/NH3/H2 molar ratio=1/1/6).