Effect of Re promoter on the structure and catalytic performance of Ni-Re/Al 2 O 3 catalysts for the reductive amination of monoethanolamine.

In this paper, Ni/Al 2 O 3 catalysts (15 wt% Ni) with different Re loadings were prepared to investigate the effect of Re on the structure and catalytic performance of Ni-Re/Al 2 O 3 catalysts for the reductive amination of monoethanolamine. Reaction results reveal that the conversion and ethylenediamine selectivity increase significantly with increasing Re loading up to 2 wt%. Ni-Re/Al 2 O 3 catalysts show excellent stability during the reductive amination reaction. The characterization of XRD, DR UV-Vis spectroscopy, H 2 -TPR, and acidity-basicity measurements indicates that addition of Re improves the Ni dispersion, proportion of octahedral Ni 2+ species, reducibility, and acid strength for Ni-Re/Al 2 O 3 catalysts. The Ni15 and Ni15-Re2 catalysts were chosen for in-depth study. The results from SEM-BSE, TEM, and CO-TPD indicate that smaller Ni 0 particle size and higher Ni 0 surface area are obtained in the reduced Ni-Re/Al 2 O 3 catalysts. Results from in situ XPS and STEM-EDX line scan suggest that Re species show a mixture of various valances and have a tendency to aggregate on the surface of Ni 0 particles. During reaction, the Ni 0 particles on the Al 2 O 3 support are stabilized and the sintering process is effectively suppressed by the incorporation of Re. It could be concluded that sufficient Ni 0 sites, the collaborative effect of Ni-Re, and brilliant stability contribute to the excellent catalytic performance of Ni-Re/Al 2 O 3 catalysts for the reductive amination of monoethanolamine.