Metal oxide sub-nanoclusters decorated Ni catalyst for selective hydrogenation of adiponitrile to hexamethylenediamine

摘要

Nickel based catalysts were decorated by metal oxide (MOx = CeO2, La2O3 or MgO) and used for the selective hydrogenation of adiponitrile to hexamethylenediamine. Additional MOx sub-nanoclusters were dispersed on surface to manipulate the electron and surface structures of nickel particles. The functional role of, e.g. CeO2 decorator, was to benefit the formation of Ni-CeO2 interfaces and acted as electron donor for the Ni active sites, rather than to change the morphology, crystallization, or the H-2 activation energy barrier. The d-band center calculated by Density Functional Theory was altered and close to the Fermi-level after CeO2 loading, rationally accounting for the accelerated reaction rate. The decorated CeO2 behaved like a double-edge sword. Excessive loading of ceria easily led to the coverage of Ni sites and destroyed the elaborated Ni-CeO2 synergy. By using Ni-Ce-3/Al2O3 with only 3 at% CeO2, adiponitrile can be completely transformed at 90 degrees C in 7 MPa H-2 for 3 h with 90% yield of hexamethylenediamine. The additional CeO2 also resulted in the enhanced stability of Ni catalyst, which maintains its high catalytic stability even after 5 reaction cycles. (C) 2019 Elsevier Inc. All rights reserved.