Influence of different microstructures of cobalt on the catalytic activity for amination of ethylene glycol: comparison of HCP cobalt and FCC cobalt

Abstract

Non-noble metal Co is an ideal catalyst for ethylene glycol amination due to its excellent dehydrogenation and hydrogenation activity. However, the influence of microstructures of Co on the catalytic activity is not clear, hindering the further improvement of its catalytic performance. In this work, two kinds of nano Co catalysts, which are separately rich in the face-centered cubic phase (fcc) and rich in the hexagonal close-packed phase (hcp), were prepared and their catalytic performances for ethylene glycol amination were compared. The results showed that fcc-Co is more active than hcp-Co. Combined with the reductive amination mechanism, the energy barriers for cleavage of chemical bonds in the dehydrogenation of ethylene glycol which is considered as the rate-determining step were determined by first-principles calculations separately on the Co (111), Co (10−11), Co (10−10) and Co (0001) facets. It was found that O–H and C–H bonds are more likely to be cleaved on the Co (111) facet, being consistent with the higher ethylene glycol conversion and yield of primary amines on the fcc-Co catalyst. In addition, the calculation results showed that the energy barriers for C–C bond cleavage in the intermediates of ethylene glycol dehydrogenation were smaller on the Co (10−11) and Co (10−10) facets, accounting for the lower primary amine selectivity on the hcp-Co catalyst.