Liquid phase acetonitrile hydrogenation to ethylamine over a highly active and selective Ni-Co-B amorphous alloy catalyst

摘要

The ultrafine Ni-Co-B amorphous alloys with Co/(Co + Ni) molar ratio (Xc) varying from 0 to I was prepared by chemical reduction of mixed Ni2+ and Co2+ ions with BH4- in aqueous solution. During liquid phase acetonitrile hydrogenation to ethylamine, the specific activity (R-m) and the intrinsic activity (TON) of the Ni-Co-B catalyst first increased and then decreased with the increase of chi(Co) from 0 to 1. The maximum activity was obtained at chi(Co) = 0.5; the value of the activity was nearly twice as that of the Ni-B or the Co-B catalyst. Treatment of the Ni-Co-B catalyst at 873 K resulted in an abrupt decrease in the activity due both to a decrease in active surface area and, especially, to the crystallization and the decomposition of the Ni-Co-B amorphous alloy. The selectivity to ethylamine increased rapidly with chi(Co) and then remained constant at chi(Co) > 0.5. The maximum yield of ethylamine could reach 93%, showing a good potential for industrial applications. According to kinetic studies and results of various characterization methods, such as ICP, XRD, EXAFS, XPS, SAED, TEM, DSC, TPD. and hydrogen chemisorption, the correlation of the catalytic performance to both the structural and the electronic characteristics was discussed briefly. The activation of the Cequivalent toN and/or C=N bonds, the promotion on the hydrogen adsorption, and the inhibition on the ethylamine adsorption were the decisive factors responsible for the excellent activity and selectivity of the Ni-Co-B catalyst. (C) 2004 Elsevier B.V. All rights reserved.