An efficient route to prepare highly dispersed metallic copper nanoparticles on ordered mesoporous silica with outstanding activity for hydrogenation reactions

Abstract

Copper nanoparticles at relatively high metal loading of 10 wt.% were successfully synthesized via incipient wetness impregnation by using polyether-functionalized ordered mesoporous silica as organic–inorganic hybrid supports. The effect of functionalized triblock copolymer Pluronic P123 (0, 25 and 50 wt.% of total triblock copolymer in gel) on the structural and catalytic properties of copper nanocomposite materials was specifically investigated. The oxide forms of materials were systematically characterized by nitrogen physisorption, SAXS, WAXS, TEM, EDXS, DR UV–vis and TPR, while the metallic forms were analysed by N₂O chemisorption, WAXS and TEM. The results indicated that the use of mesoporous silica hybrids leads to highly dispersed supported copper nanoparticles (dispersions in the range of 43–57%) displaying excellent activity in the hydrogenation of cinnamaldehyde. The average particle size was shown to decrease from 2.3 to 1.7 nm with the increase in the amount of functionalized triblock copolymer from 0 to 50 wt.%. Under standard test conditions, all the nanosized copper catalysts showed high catalytic activity but selectivity towards the saturated aldehyde. Further improvements in activity and selectivity towards the unsaturated alcohol were achieved by increasing the hydrogen pressure and applying a two-step reduction–oxidation pre-treatment, respectively. The structure and controllable properties of nanoscale copper materials developed herein, both oxidic and metallic forms, make them very attractive candidates for both fundamental research and practical catalytic applications.