Preparation of metal and metal oxide doped silica hollow spheres and the evaluation of their catalytic performance

The aim of this study was the synthesis of silica hollow spheres-based materials doped with metal nanoparticles or metal oxides. Two different strategies based on the use of polymer colloids and cetyltrimethylammonium bromide (CTAB) as dual templates were developed. The first strategy involves the use of soap-free emulsion polymerization for the trapping of metal nanoparticles (Ag and Ni) and in the polymer structure. The second strategy exploited carboxyl groups present on the surface of the polymer particles for the adsorption of metal salts (Ni and Fe). A complete porous SiO2 shell was generated around the polymer colloids using a Stober method and CTAB to guide the silica shell growth. The obtained silica hollow sphere displayed either yolk-shell distribution of the doping elements or a uniform oxide deposit on the interior surface of the silica capsules. The versatility of the synthesis method and the catalytic performance of the materials were demonstrated in the case of Fe@SiO2 for a Fischer-Tropsch process.