Regulation mechanism of Ce on the surface structure and hydrogen activation behavior of Ni/γ-Al2O3 catalyst and its application in selective hydrogenation of pyridine

Cerium modification modulates the surface acidity and metal-support interactions of the Ni/γ-Al 2 O 3 catalyst. • Cerium species can not only suppress the formation of strong acid sites, but also regulate the adsorption configuration of pyridine molecules. • The enhanced electron transfer from cerium to nickel improves the reducibility and hydrogen activation performance of nickel. • The Ni/Al–Ce(10) catalyst achieves high catalytic activity in the pyridine hydrogenation reaction. To address the key challenge of achieving both high conversion and high selectivity in the selective hydrogenation of pyridine, this paper proposes a strategy of precisely modulating the surface acidity and metal–support interaction of an alumina support via cerium (Ce) modification. The study shows that Ce modification effectively suppresses the strong acid sites on the alumina surface, thereby promoting the desorption of the target product, piperidine. Meanwhile, Ce doping induces a flat-lying adsorption configuration of pyridine molecules, which is more favorable for the saturation hydrogenation of the aromatic ring, significantly enhancing the hydrogenation selectivity. Ce species facilitate electron transfer to the nickel active centers, increasing the local electron density around the nickel sites. This reduces the binding energy of nickel, enhances its reducibility, and effectively inhibits the formation of nickel aluminate spinel (NiAl 2 O 4 ), thereby improving the intrinsic hydrogenation activity of the catalyst. Under the reaction condition of 200 °C, the Ni/Al–Ce (10) catalyst achieves a pyridine conversion of 99.5% and a piperidine selectivity of 97.4%. Download: Download high-res image (281KB) Download: Download full-size image