Langmuir, Vol.36, No.2, 576-584, 2020
Preparation of Silica@Silica Core-Shell Microspheres Using an Aqueous Two-Phase System in a Novel Microchannel Device
In the present work, a novel microchannel device was developed and used for the preparation of core-shell microspheres combining with a dextran/poly(ethylene glycol) diacrylate (DEX/PEGDA) aqueous two-phase system. Silica@silica core-shell micro spheres were prepared as a model material. Silica@silica core-shell microspheres with different sizes of cores and thicknesses of shells were prepared by using different flowrate ratios of DEX/silica and PEGDA/silica aqueous solutions. The content of colloidal silica and the calcination temperature have a significant effect on the texture properties of the prepared core-shell microspheres. The surface area decreased from 199 to 177 m(2)/g with an increase in the colloidal silica content from 30 to 60 wt %. For a specific colloidal silica content (50 wt %), with the increase in calcination temperature from room temperature to 650 degrees C, the total pore volume went through a maximum of 0.7 cm(3) g(-1) with a surface area of 178 m(2) g(-1) and pore size of 7.32 nm at 450 degrees C. Due to the accumulation of metal nanoparticles in DEX, different metal nanoparticles (Ni and Pd) were successfully introduced into the core of the core-shell microspheres for the preparation of silica/metal nanoparticles@silica core-shell microsphere catalysts. The catalysts showed similar catalytic performance as the metal nanoparticles for hydrogenation of 4-nitrophenol with a conversion higher than 95%. However, the core-shell microsphere catalyst is much easier to recover. The reuse experiments indicated that the core-shell catalyst has high stability.