Rational design of integrated nanocatalysts with hollow mesoporous transition metal silicates for chemoselective hydrogenation of cinnamaldehyde

Abstract

The chemoselective hydrogenation of α, β-unsaturated aldehydes are highly dependent on both the electronic and structural effects of the catalysts. In this study, hydrogenation of cinnamaldehyde was carried out over a series of integrated nanocatalysts consisting of Pt nanoparticles and hollow transition metal silicates which were prepared by either one-pot method or sol-immobilization method. The hollow transition metal silicates not only served as mesoporous support materials for high-efficient loading of Pt but also provide tunable Fe/Ni as promoters to improve the catalysis process. It was revealed that using hollow Fe silicate as support generally exhibited low activity but high selectivity due to the strong interaction of CO bond, whereas, using hollow Ni silicate as support showed enhanced activity but low selectivity, which was attributed to the different electronic effects as evidenced by H2-TPR and XPS. In addition, electronic effects among the ternary catalysts with Pt loading on Fe-Ni bimetallic silicates were critical to the observed high turnover frequencies, that is, Pt sites contributed to H2 activation, Fe sites favored the preferential adsorption of CO bond in cinnamaldehyde, while Ni sites promoted the formation of Pt0 rather than Ptδ+.