A novel core–shell nanocomposite Ni–Ca@mSiO₂ for benzophenone selective hydrogenation

A novel core–shell nanocomposite Ni–Ca@mSiO₂ was first prepared by a modified Stöber method in this paper. It has a core–shell structure with Ni (about 8 nm in diameter) and Ca as the cores and mesoporous silica as the outer shell, as proven by the transmission electron microscopy. This nanocomposite exhibited good catalytic performance in the selective hydrogenation of benzophenone, with 96.1% conversion and 94.9% selectivity for benzhydrol under relatively mild reaction conditions. It was demonstrated that addition of small amounts of alkaline Ca can not only markedly improve the dispersion of the active species but also tune the acid–base property of this nanocomposite, resulting in the efficient suppression of benzhydrol dehydration to achieve a high selectivity. Furthermore, the core–shell nanocomposite Ni–Ca@mSiO₂ can be recycled four runs without appreciable loss of its initial activity, more stable than the traditional supported nanocatalyst Ni–Ca/mSiO₂. It was suggested that the outer mesoporous silica shell of Ni–Ca@mSiO₂ can prevent both the aggregation and the leaching of the active Ni species, accounting for its relatively good stability.