External [1 1 1] facets on nanorod gamma alumina boosts catalytic reductive amination of carbonyl compound to primary amine

Hydrogen spillover had played a significant role in catalytic processes involving reducible oxide supported metal catalyst and hydrogen molecule. Herein, crystal plane regulative hydrogen spillover strategy for the effective reductive amination on Ni/Al2O3 was developed. A rod-like alumina supported Ni catalyst with primarily external (1 1 1) facets was prepared. In the presence of NH3 and H2, Ni/Al2O3 (1 1 1) exhibited a turnover number of 30.4 h−1, which was 136-fold higher than that of Ni/Al2O3 (1 1 0) in the reductive amination of furfural to furfuryl amine. For the Ni/Al2O3 (1 1 1) catalyst, Al2O3 (1 1 1) facets exhibited strong Lewis acidity, resulting in an enhanced H affinity of Al2O3 (1 1 1) and a positively charged of Ni through electronic interaction. It was revealed that strong H affinity of Al2O3 (1 1 1) and positively charged Ni sites significantly promoted hydrogen migration from Ni surface to Al2O3 (1 1 1) facets, which effectively prevented the Ni sites from hydrogen poisoning and enhanced the adsorption and activation of NH3 and intermediates for reductive amination. Consequently, the activation energy of Schiff base reductive ammonolysis was obviously reduced, resulting in high inherent activity for furfural reductive amination to furfuryl amine. This work developed a new strategy for high efficiency reductive amination catalyst in terms of hydrogen spillover effect.